Final Report.pdf

S

A summary of the experiance gained

King Fahd University of Petroleum and Minerals
College of Engineering and Physics
Electrical Engineering Department
COOP Final Report
Power System in Saudi Arabia
Saudi Aramco
Dhahran
Hussain Al-Hussain
201846020
COOP Advisor: Dr. Motaz Alfarraj
March 23, 2023
I
Abstract
This report will present my training experience as a COOP student in Saudi Aramco,
specifically at Power Operation Department as well as Power Planning Department. This
report will delve into several subjects regarding power system in Saudi Arabia. Within it,
the affiliate structure of the power system will be discussed. Also, this report will elaborate
on various power generation topics, in which kingdom’s reliability on different
technologies and fuels are going to be highlighted.
A plan to expand the kingdom’s gas network will be outlined. In addition, A brief
discussion on different transmission towers and poles will be introduced. More
importantly, the Saudi Arabian Grid Code and Transmission Use of System agreement will
be succinctly discussed. Furthermore, an inclusive revision of different electrical
equipment, Uninterruptable Power Supplies and Power Transformers for instance, is
presented.
Three case studies are presented in this report. The first case study tests the validity to reuse
a CO-9 Protective Relay. The second case study investigates the root causes of the power
outage occurred in Power Operation Department, while the third one focuses on
establishing a correction factor that will make two meters, installed in different locations,
read the same energy demand.
II
Acknowledgement
Thanks to Allah, for all the blessings that I, my family, and all the people have in this life.
Thanks to my parents for their guidance and support continuously since I was born and
though every milestone through my life.
I am deeply thankful to everybody for helping me reach this milestone. My sincere
gratitude goes to my supervisor in Aramco, Mohammed AL-Ghamdi, for his invaluable
support, guidance and mentorship through my training period. I also want to express my
appreciation to my colleagues at Aramco, Khalid Al-Rashidi, Rashed AL-Olayan, Muhana
AL-Dakheel, Amer Alsubaie, and Murali, for their collaboration and support, which made
every challenge surmountable.
Turning to my academic pursuits, I am grateful to Dr. Motaz Alfarraj, my advisor at
KFUPM, for his guidance and insights that enriched my academic experience. I extend my
heartfelt thanks to all who contributed, both directly and indirectly, to my journey, as your
contributions have left a lasting impact. This achievement is the result of the combined
efforts and support of these remarkable individuals. Thank you all for being part of my
success.
King Fahd University of Petroleum and Minerals, Dhahran
Electrical Engineering Department
III
Table of Content
CHAPTER 1:INTRODUCTION ....................................................................................... 1
CHAPTER 2:TRAINING EXPERIENCE............................................................................. 5
2.1. MEMBERS OF POWER SYSTEM.................................................................................... 5
2.2. POWER GENERATION.............................................................................................. 12
2.3. POWER TRANSMISSION ........................................................................................... 25
2.4. POWER DISTRIBUTION............................................................................................. 40
CHAPTER 3:CASE STUDY I - ELECTROMAGNETIC RELAY TEST ..................................... 66
3.1. INTRODUCTION...................................................................................................... 66
3.2. METHODOLOGY..................................................................................................... 66
3.3. FINDINGS.............................................................................................................. 69
3.4. ANALYSIS.............................................................................................................. 70
3.5. CONCLUSION......................................................................................................... 70
CHAPTER 4:CASE STUDY II - POWER OUTAGE IN POD................................................ 71
4.1. INTRODUCTION...................................................................................................... 71
4.2. FIRST CASE ........................................................................................................... 71
4.3. SECOND CASE........................................................................................................ 71
4.4. ANALYSIS.............................................................................................................. 72
4.5. CONCLUSION......................................................................................................... 74
CHAPTER 5:CASE STUDY III - METERS’ CORRECTION FACTOR..................................... 75
5.1. INTRODUCTION...................................................................................................... 75
5.2. METHODOLOGY..................................................................................................... 76
5.3. FINDINGS.............................................................................................................. 78
5.4. ANALYSIS.............................................................................................................. 79
5.5. CONCLUSION......................................................................................................... 80
CONCLUSION............................................................................................................ 81
RECOMMENDATION................................................................................................. 82
REFERENCES............................................................................................................. 83
APPENDIX A: COOP PLAN ......................................................................................... 87
APPENDIX B: CALCULATING METERS’ CORRECTION FACTOR...................................... 89
IV
List of Figures
Figure 1: Industry Structure of Saudi Energy Sector [3]............................................ 6
Figure 2: Operation of a Brayton Cycle Power Plant [7]......................................... 13
Figure 3: Operation of a Rankine Cycle Power Plant [10]....................................... 14
Figure 4: Operation of Combined Cycle Power Plant [12]...................................... 15
Figure 5: Current Fuel Mix in Saudi Arabia ............................................................ 18
Figure 6: Comparison Between Domestic and International Fuel Price [16]. ......... 19
Figure 7: Emission of Fuels Currently Used in Saudi Arabia [17]. ......................... 19
Figure 8: Saudi Arabian Oil Fields and Oil Facilities [19] ...................................... 26
Figure 9: Saudi Arabia’s Pipelines [18] ................................................................... 26
Figure 10: Saudi Arabia’s Shuaiba’s Pipeline............................................................ 27
Figure 11: An Illustration of Different Electrical Towers and Poles [20].................. 28
Figure 12: Transmission Tower Classification Based on Supply Circuits [21]. ........ 29
Figure 13: Components of a Transmission Tower ..................................................... 30
Figure 14: Procedure of Connecting to National Grid ............................................... 33
Figure 15: Connection of Off-Site Facilities.............................................................. 35
Figure 16: Equipment of Online Double Conversion UPS System [25].................... 42
Figure 17: Batteries of the UPS System..................................................................... 44
Figure 18: Representation of Transfer Switches ........................................................ 45
Figure 19: A Photograph of UPS Rectifier................................................................. 46
Figure 20: Illustration of a UPS Inverter.................................................................... 47
Figure 21: Left View of a Power Transformer........................................................... 51
Figure 22: Front View of a Power Transformer......................................................... 51
Figure 23: Power Transformer Components [28]. ..................................................... 52
Figure 24: Dehydrating Breather of Power Transformer [29].................................... 52
Figure 25: Connection of Insulation Resistance Test [30] ......................................... 54
Figure 26: Example of an SFRA Test Measurement [31].......................................... 55
Figure 27: An illustration of MCB, MCCB and RCCB, respectively........................ 57
Figure 28: A Photograph of a Breaker Panel [35]...................................................... 57
Figure 29: An Illustration of Coordination Characteristic. ........................................ 58
Figure 30: First Page of ANSI Standard Device Number [36]. ................................. 60
Figure 31: Second Page of ANSI Standard Device Number [36].............................. 61
Figure 32: Components of a CO-9 Electromagnetic Relay........................................ 65
Figure 33: CO-9 Magnetic Relay Characteristic Curve [37]...................................... 67
Figure 34: A Photograph of the Megger SVERKER 750 [38]................................... 68
Figure 35: Connection of SVERKER 750.................................................................. 68
Figure 36: Connection of CO-9 Relay........................................................................ 68
Figure 37: Pollution Flashover Progression of insulators [39]................................... 72
Figure 38: The Process of Contamination Discharge on Polluted Insulators [40]..... 73
Figure 39: Sorted Percentage Difference ................................................................... 77
Figure 40: Expected Correction Factor Trendline According to SEC. ...................... 78
Figure 41: Relation Between Distance and Correction Factor................................... 80
V
Figure 42: Main and Check Meters’ Readings Against Time.................................... 90
Figure 43: Difference Between Main meter and Check meter................................... 91
Figure 44: Demonstration of the Filter Function........................................................ 91
Figure 45: Lowest to Highest % Difference............................................................... 92
Figure 46: Procedure for Filtering Best 90% Readings.............................................. 93
Figure 47: Correction Factor Trendline and Slope..................................................... 94
VI
List of Tables
Table 1: IPP and IWPP Groups [3]............................................................................... 7
Table 2: Renewable Energy Projects Overseen by MoE [4]......................................... 8
Table 3: Pros and Cons of Single Cycle Plants [8] [9]. .............................................. 14
Table 4: Scenario 1, No Change in Current Prices. .................................................... 20
Table 5: Scenario 2, HFO Price will be more expensive than gas going forward. ..... 20
Table 6: Conversion Factors. ...................................................................................... 21
Table 7: Summary of Given Parameters ..................................................................... 21
Table 8: Steps to Find Daily Fuel Consumption of HFO and Sales Gas. ................... 22
Table 9: Total Costs of Fuels in Scenario 1. ............................................................... 23
Table 10: Total Costs of Fuels in Scenario 2. ............................................................... 24
Table 11: Tariffs of Different End-users....................................................................... 37
Table 12: Given Parameters.......................................................................................... 37
Table 13: Cost of Purchased Energy per Load Type .................................................... 37
Table 14: TUoS Payment with Different Load Factors ................................................ 38
Table 15: Total Cost of Transferred Energy ................................................................. 38
Table 16: Cost Comparison (Purchased Energy – Transferred Energy)....................... 39
Table 17: Most Common ANSI Device Numbers ........................................................ 62
Table 18: Results of Time Dial Test ............................................................................. 69
Table 19: Results of Instantaneous Relay Coil Test ..................................................... 69
Table 20: Results of Current Tap Setting Test.............................................................. 69
Table 21: Summary of Facilities’ Correction Factors................................................... 79
Table 22: Assumed Meter’s Readings .......................................................................... 89
Table 23: Filtered Data with % Difference................................................................... 92
Table 24: Re-Filtered Meter’s Readings....................................................................... 94
1
CHAPTER 1: INTRODUCTION
As you turn on the kitchen light switch, a circuit is closed connecting the breaker inside
the house. The end connection of this breaker is at the transformer, installed outside the
house. The cables that supply this transformer are hidden underground, and coming from
a substation in which the voltage, specifically inside Saudi Arabia, is stepped down from
13.8 KV to 600 V for residential use.
Inside this substation, protective equipment, like switchgear, relays, breakers, control
panels and other equipment serves to prevent the occurrence of electric faults. At this
substation, the cables are raised from underground to above a transmission tower. Multiple
types of transmission towers carrying the cables exist. The general rule is, the more voltage
contained in the cables, the higher and stronger the transmission towers are. This is to
protect people from being shocked, since more voltage means greater distance that
electrons can jump for.
The cables, known as transmission lines, extend to pass through several substations, to
finally reach the generators, found in the eastern and western side of the kingdom. The
fuels, specifically crude oil and gas, extracted in the eastern side of the country, are
primarily Aramco’s main industry. The company is introduced next.
Saudi Aramco (the Arabian American Oil Company) is one of the largest integrated energy
and chemicals companies in Saudi Arabia. Saudi Aramco creates value across the
hydrocarbon chain, and deliver economic and societal benefits to the people and
communities around the globe. Saudi Aramco aims to (1) reinforce its leading position in
2
oil and gas exploration and production, (2) enable the sustainable development of the
Kingdom, and (3) lead the way in technology development and innovation [1].
Currently, Saudi Aramco is developing five mega projects which are: Fadhili Gas Plant,
Manifa Bay, Sadara Chemical Company, Shaybah Power Plant and Wasit Gas Plant.
Fadhili Gas Plant reflects Saudi Aramco’s dedication to reduce emissions, increase
supplies of cleaner burning natural gas, and free up more crude oil for value-added refining
and export. The Manifa shallow water oil field is one of the world's biggest producing oil
fields. 328,500,000 barrels were produced in Manifa by 2017 [2]. The Sadara Chemical
Company is a joint venture between both ARAMCO and the Dow Chemical Company.
Sadara Chemical Company is constructing in Jubail Industrial City the world’s largest
chemical complex ever built in a single phase. Shaybah Power Plant is a super-giant power
plant under the control of Saudi Arabia which is located in the northern edge of the Rub'
Al-Khali desert. Wasit Gas Plant is operating gas-fired power station in Al-Jubail, Eastern,
Saudi Arabia, that supplies about 1400 MW.
Speaking about my experience in Saudi Aramco, I was assigned with the Power System
Planning department first in Saudi Aramco, to (1) have an introduction about the
company’s goals, (2) have an overview to the power grid in Saudi Arabia, and (3) learn
networking skills needed in the workplace. After that, to connect my theoretical knowledge
with practical applications, I was sent temporarily to the Power Operation Department
(POD). Until the 30th
of March, I was rotating between units weekly to have an overview
of distribution stage activities and operations. The Power Operation department hosts six
units, each will be discussed briefly in the next page.
3
1) Maintenance Planning unit is responsible for creating plans for the other units,
reviewing ongoing projects and dealing with contractors.
2) Uninterruptable Power Supply (UPS) & Renewables unit is responsible for
maintaining the UPS System by undertaking weekly inspections and minor/major
preventive maintenance.
3) Power Service unit is responsible for testing and maintaining the healthiness of heavy
electrical equipment, including transformers, switchgears, gas switches, breakers, etc.
4) Electrical System Operation unit controls Aramco electrical network. It is
responsible for isolating any electrical equipment before maintenance and investigation
on the locations of electric faults.
5) Power Lines & Cables unit is responsible for mid/high voltage cables replacements,
and inspection and maintenance on transmission towers.
6) Power Relay unit is responsible for troubleshooting and maintaining all of protective
relaying and control systems within substations, power plants, large motors, etc.
After completing my assignment in the Power Operation Department, I returned to the
Power System Planning Department and joined three divisions, namely, National
Regulations, Kingdom Utilities and Power Demand Analysis. The activities that these three
departments are concerned with are discussed next.
7) National Regulation division is the point of connection between Aramco and the
government. It is where codes, rules and regulations are reviewed to be considered in
the company’s current and future projects.
4
8) Kingdom Utilities division deal with all parts of the kingdom, in regard to the planning
of its utilities, for example, forecasting and planning fuel consumption, energy to be
generated both renewable and non-renewable, and energy transmission and
consumption locations.
9) Power Demand Analysis division is concerned with reviewing the data used to
calculate peak demand, as well as deciding whether to transmit excess energy using
TUoS (Discussed in subsection 2.3.4), or sell the excess energy as a spill.
Through learning and working with the different units and divisions mentioned above, I
gained knowledge in different spectrums, improving my skills and helping me realize the
future of a typical power electrical engineer.
This report summarizes important experience gained when working in Aramco,
specifically in chapter 2, and presents three case studies in the remaining chapters, where
chapter 3 and 4 were done in the Power Operation Department, while chapter 5 is
completed in Power Planning Department.
5
CHAPTER 2: TRAINING EXPERIENCE
This chapter summarizes my training experience in the COOP period. Section 2.1 discusses
the structure of the power system, specifically the members who participate, regulate, or
authorize the activities within the Power System. Section 2.2 explains different subjects
about power generation in the kingdom. Section 2.3 explores the structure and material of
transmission towers and poles. It then dives deep into regulations and policies that control
the national grid. Section 2.4 summarizes characteristics of different necessary equipment
used in electrical substations.
2.1. Members of Power System
There are six players in the energy market, two of them are considered vital. The first and
most important member in the energy market is the Ministry of Energy (MoE). MoE
authorizes the opening of an energy field, for example, the opening of Solar energy market
in the kingdom. MoE plans for the future, say, the next 10 years, before the authorization.
Moreover, MoE is considered an important member of the power system, and therefore, a
deeper view about MoE is provided in subsection 2.1.1. Second is Water & Electricity
Regulatory Authority (WERA). WERA is the entity who regulates energy fields by
establishing rules and policies to maintain the quality of energy services provided by
companies. Also, WERA focuses on regulating the activities in the energy sector. Because
of its importance, more details about WERA are provided subsection 2.1.2.
Third, Principal Buyer (PB) is the sole buyer & seller of electricity. PB is sometimes
referred to as Saudi Power Procurement Company. Fourth, National Grid, consisting of
Transmission Service Provider (TSP) and Distribution Service Provider (DSP), is wholly
6
owned by Saudi Electricity Company (SEC). Fifth are the Generators, the ones responsible
for generating energy, whether it is renewable or non-renewable, such as Aqua Power,
Saudi Aramco Power Company, or SEC. Sixth are the Consumers, the ones who consume
the energy. These can be industrial users such as machines in factories, can be citizens
living in residential zones, can be employees working in commercial buildings such Clock
Tower found in mecca, or can be for governmental services, schools and hospitals for
instance. The current electricity industry structure is shown below in Figure 1. In the figure,
IPP and IWPP are the groups of the companies illustrated in Table 1.
Figure 1: Industry Structure of Saudi Energy Sector [3].
7
Table 1: IPP and IWPP Groups [3]
Group Members
Independent Power Producer (IPP) Hajr for Electricity Production Company
Durmah Electric Company
Rabigh Electric Company
Al-Mourjan for Electricity Production
Company
Independent Water & Power Producer
(IWPP)
Jubail Water & Power Company
Shuaibah Water & Power Company
Shuqaiq Water & Power Company
2.1.1 Ministry of Energy
Ministries have the highest responsibility within their sectors. They are the hand of the
government that regulates all activity aspects of their dedicated sector. Accordingly, MoE
monitors and regulates all activity aspects of energy sectors. MoE vision manifests itself
in the aspiration of being an international leader in the field of energy and innovation.
Furthermore, to achieve that vision, MoE established the mission; to be the leader in the
energy sectors by first establishing development plans and programs that improve the
added value of the sector, i.e., improve the service quality to raise the price of the sector
services. And more importantly, by overcoming the economic challenges to maintain
kingdom’s wealth, for instance, kingdom’s full dependence on fossil fuels. One of the
solutions that MoE applied was to build renewable energy projects, shown on Table 2,
where IPP PV stands for Independent Power Producer Photovoltaic.
8
Table 2: Renewable Energy Projects Overseen by MoE [4].
Project Type Location Production Capacity
IPP PV Rahfa 20 MW
IPP PV Medina 50 MW
IPP PV Qurayyat 200 MW
IPP PV Rabigh 300 MW
IPP PV Jeddah 300 MW
Wind Farm Dumat Al-Jandal 400 MW
IPP PV Shuaibah 600 MW
IPP PV Sudair 1500 MW
IPP PV Sakaka 9500 MW
MoE strives to accomplish its mission by achieving the following objectives: to (1) lead
global energy markets, (2) optimize the production and consumption of hydrocarbons,
which is a raw material used in lubricants, fuels, plastic, explosives, and other industrial
chemicals, (3) be highly efficient in economic growth and consumption, and (4) maintain
sustainability of the supplies by preserving the fortunes of the kingdom. In addition, for the
reader to know which specific fields MoE works on, the most important units [5] that make
up MoE are discussed next.
1) Optimum Allocation of Energy Resources
Optimum Allocation of Energy Resources unit is responsible for receiving and reviewing
orders related to allocating energy resources. One of the main jobs of this unit is to create
9
licenses for the pipelines of the energy distribution network. In fact, the unit also
establishes the rules in coordination with energy source requester in order to get the license.
More importantly, scrutinizing whether the established rules were compiled is within the
unit responsibilities.
2) Policy and Strategic Planning
Policy and Strategic Planning is responsible for collecting and revising data to develop
strategic plans and complete policies for the energy sector.
3) Development of Local Content, Crisis Management, and Risk
This unit is responsible for increasing domestic production in the energy sector by working
with all energy concerned parties. Also, the unit is responsible for creating jobs to reduce
unemployment in the kingdom. Last, searching for possible risks in the national grid is part
of unit’s obligations.
4) Electricity Affairs
Duties of Electricity Affairs unit are demonstrated in: (1) developing energy services that
increases the added value of energy sector, (2) reinforcing the electrical grid to have enough
capacity, that is, to receive different kinds of energy, especially the promised renewable
energy projects. Finally, (3) inspect whether users of the national grid complied with rules
mentioned in the Distribution Code.
10
5) Renewable Energy
Renewable Energy unit is solely obligated to develop strategic plans that advance
renewable energy projects. Part of their work is to study the global energy market and gain
insight from other countries, to apply the learnt information in supporting domestic
projects.
6) Regulation of Petroleum and Gas
The responsibility of Regulation of Petroleum and Gas unit is to supervise and regulate all
activity aspects associated with the three sectors, namely. Petrol sector, gas sector, and
petrochemical sectors.
7) International Relations and Cooperation
Creating and reinforcing a strong relationship between Saudi Arabia and other countries,
both gulf and non-gulf, in pertaining to energy sectors is the unit’s main objective. The unit
also studies and analyzes the international shared objectives, which helps in identifying
areas of cooperation, and avoiding any potential conflicts between the kingdom and
neighboring countries.
8) Sustainability and Climate Change
The duties of this unit are many. Therefore, the most general duties are only mentioned.
The first duty is giving the needed support against climate change, specifically, the yearly
increase of temperature due to global warming. The second duty is to participate in putting
strategies to increase clean energy as illustrated in Table 2. The third duty is to develop the
11
environmental policies related to the energy sector, while the last one is to monitor the
implementation of the carbon circular economy and promote it. In fact, Carbon circular
economy manifests in creating something that is known to be dismantled and restored later,
because even though the kingdom’s resources are abundant, they can be easily depleted if
not used wisely. These are the vital units that make up MoE. WERA is discussed next.
2.1.2 Water & Electricity Regulatory Authority
WERA regulates the electricity and water desalination sector within the Kingdom.
WERA’s vision is to make water and electricity reach a sustainable state, and at the same
time, guarantee to give the best services that comply with the global standards in terms of
quality, efficiency and inclusivity [6]. WERA will achieve its vision by guaranteeing to the
consumers that electrical service providers deliver services of high quality, complete,
dependable and at a reasonable price. Next, the objectives of the WERA are to:
1) Create a suitable environment that encourages competition between water and
electricity service providers.
2) Encourage investors to share in improving power generation and water desalination
sectors, and enable them to make economic profits. The reasons to do so is
demonstrated in this case. Whenever investors invest in the kingdom, they will open an
outlet of their company, business, or enterprise in Saudi Arabia. Because of that, the
branch opened in Saudi Arabia must comply with all the rules and policies, for
example, nationalization of the workforce, which will decrease the rate of
unemployment. In addition to that, the 15% tax payment must be submitted for any
12
service or product presented by the branch to the kingdom, increasing kingdom’s
wealth.
3) Protect Public interest and consumers’ rights by providing high quality water and
electricity services with reasonable prices.
2.2. Power Generation
This section briefly explains the diverse generation technologies employed in Saudi
Arabia. Following this, the extent to which the kingdom relies on the mentioned
technologies is outlined. After that, this section explains the kingdom’s dependence on
various fuels used to generate power. Finally, this section concludes with an exercise that
demonstrates how to calculate the consumption of fuels in a power plant.
2.2.1 Generation Technologies
Three technologies are applied when generating electricity, these are: Simple Cycle,
Combined Cycle and Co-generation. The process of each technology with its operational
times is discussed briefly Next.
First is the Simple Cycle. Because of its fast start up, Simple Cycle technology is used
whenever power demand is high, especially at noon, when numerous air conditioners are
operating. The process of Simple cycle technology is as follows: A simple cycle power
plant (1) pumps the received air, (2) mixes it with natural gas and burns it to produce a
high-pressure (HP) gas, (3) uses this gas to move the turbine which results in moving
generator’s rotor; thus, produce electric energy. This is called Brayton Cycle, depicted in
Figure 2.
13
Figure 2: Operation of a Brayton Cycle Power Plant [7].
Another method to do the same job in which water is used in place of air is called the
Rankine cycle, illustrated in Figure 3. The process of a Rankine cycle power plant is
explained next. First, water goes into a pump, to increase the water pressure. Second, the
HP water goes into a boiler to be vaporized and converted into steam. Third, this steam is
used to move the turbine, and the turbine will move the rotor of a generator, thus generating
electricity. Fourth, outlet steam is cooled and condensed to be reused in generating the
steam, starting the loop from the beginning. Additionally, the advantages and
disadvantages of a Simple Cycle power plant are briefly mentioned on Table 3.
14
Table 3: Pros and Cons of Single Cycle Plants [8] [9].
PROS CONS
Fast Start-up, in as low as minutes Low Heat Efficiency (33.8%)
Cheap Construction Expensive Operation & Maintenance
Space-saving Much Emission is Produced
Figure 3: Operation of a Rankine Cycle Power Plant [10].
Second is the Combined Cycle. Combined Cycle technology is the combination of both
Brayton Cycle and Rankine Cycle. In Combine Cycle, the same fuel is used in both cycles.
The difference between Single Cycle and Combined Cycle is in the use of exhausted air.
To explain, whereas Single cycle generators exhaust all the low-pressure gas, Combined
cycle generators utilize it to produce more power. Utilizing the exhausted gas resulted in
almost doubling the efficiency of the generators, from 33.8% (Single cycle generators) to
15
at least 60% (Combined Cycle generators), and on top of that, the CO2 emission is reduced
by 50% [11].
The operation of Combined cycle technology is demonstrated in Figure 4. The blue side
represents the Brayton Cycle, while the green side is where the exhausted air from Brayton
Cycle is exploited (Rankine Cycle). The complete process of a combined cycle power plant
is explained next. First, the exhausted air enters the heat recovery steam generator, which
vaporizes the water using the heat of the exhausted gas. Then, HP steam is used to move
the turbine in order to generate electricity. After using the HP steam by the generator, a
low-pressure (LW) steam resulted, and is injected to the air condenser to convert steam
back into water, and water is pumped to be reused by the heat recovery steam generator.
Figure 4: Operation of Combined Cycle Power Plant [12].
16
Last Power technology is Co-generation. Co-generation is indeed a part of Combined Cycle
technology. Co-generation is the production of both electricity and Steam. In Combined
Cycle technology, steam is used only to generate more electricity. However, in
Cogeneration, steam is sold as is, since it can be used in a much wider scope. One
application is to use the heat of the steam to separate chemical compounds of the gas that
is used in Brayton Cycle, e.g., separate methane and ethane from the gas to sell each one
individually. Another application is to use steam as a source that moves pumps. This is
done by moving the steam through a turbine that rotates a pump, to increase the pressure
of other gases or liquids. A third application is to heat other fluids using steam. For the
power sector, companies such as SEC prefer combined cycle technology over Combined
Cycle technology. However, in the context of oil and gas companies like Aramco, co-
generation technology proves to be a more advantageous and practical option.
To summarize, whenever electricity is needed for demand peaking time, Simple cycle
plants are used. If electricity is needed continuously, Combined Cycle plants are used. If,
however, steam is needed for any such applications, Co-generation plants are used.
2.2.2 Generation Mix
By generation mix, the author means the amount of reliance on different technologies used
in Saudi Arabia. The main three technologies used in electricity generation inside Saudi
Arabia are: Gas Turbine (Brayton Cycle), Steam Turbine (Rankine Cycle), and Combined
Cycle. The total energy generation of kingdom of Saudi Arabia, as per 2017 data, is 289
TWh, with power capacity of 90 GW distributed between the three technologies as 49.8%
for Steam Turbines, 35.4% for Gas Turbines, 13.9% for Combined Cycle units [3].
17
The average capacity of one unit of Steam Turbine (ST), Gas Turbines (GT), and
Combined Cycle (CC), is 37 MW [13], 29.98 MW [14], and 820 MW [15] respectively. In
other words, an estimation of 1200 units of STs, 1050 units of GTs and 15 units of CC exist
in the kingdom. As will be shown later, gas turbines exist on the eastern side of the country,
because of the much availability of gas there, and steam turbines exist on western side of
the country, because of the easy access to water at that location. The eastern and western
sides of the country supply energy to the whole country.
According to KSA 2030 Vision, our generation mix will shift to depend solely on the two
technologies, namely, GTs and Renewable Energy technology. To be exact, the capacity
of the country must be 50% for Renewables, and 50% for GTs. The reader is suggested to
refer to Table 2 to check the current progress of KSA towards having 50% renewable
energy in the country.
2.2.3 Fuel mix in the kingdom
As per Aramco’s 2017 data, the current fuel mix for the kingdom, as depicted in Figure 5,
is distributed between four types of fuels. These are Natural Gas, Crude Oil, Heavy Fuel
Oil (HFO) and finally Diesel. Most of the power generated is by combusting Natural Gas,
making up 44% of power generation capacity. On the other hand, Diesel, the least burned
fuel, makes up only 7% of the generation capacity. Reasons for that are further explained
afterwards. In the middle are HFO and Crude Oil, making up 28% and 21% of the capacity,
respectively.
18
Figure 5: Current Fuel Mix in Saudi Arabia
As mentioned before in 2.2, one objective of vision 2030 is to stop using liquid fuels
completely, and shift the dependance on gas and renewable energy. This is to decrease
energy costs, by removing the subsidies given to liquid fuel sellers; and to protect the
environment, by reducing carbon emissions produced from fuel combustion. To illustrate,
Figure 6 shows the significant reduction in domestic diesel price, which can be recovered
by removing Saudi governmental subsidies, and Figure 7 in turn demonstrates a significant
difference in the emissions of gas compared to the other liquid fuels. One third of the
emissions coming out from combusting HFO can be eliminated if gas is used instead.
44%
28%
21%
7%
CONSUMPTION OF DIFFERENT FUELS IN SAUDI
ARABIA
Natural Gas
HFO
Crude Oil
Diesel
90 GW
19
Figure 6: Comparison Between Domestic and International Fuel Price [16].
Figure 7: Emission of Fuels Currently Used in Saudi Arabia [17].
23.14
71.73
119.85 116.84
0.00
20.00
40.00
60.00
80.00
100.00
120.00
140.00
Diesel GAS
Price
of
Fuel
(SAR/MMBtu)
Diesel Price Comparison
Domestic International
0.27
0.18
0.25
0
0.05
0.1
0.15
0.2
0.25
0.3
HFO GAS Diesel
Emission
Factor
(Kg/KWh)
Emission of Different Fuels
20
2.2.4 Fuel Consumption Exercise
The problem statement is as follows. Consider Rabigh Power Plant facility with the
following parameters:
• The plant has 4 units running on HFO.
• The first two units are 300 MW while the other two units are 800 MW
• Efficiencies at 25% and 35%, respectively.
• Plant utilization rate is 90%, with annual interest rate of 6%
Assuming steady demand and steady generation throughout the year, calculate:
1) The plant’s daily fuel consumption using HFO.
2) The plant equivalent consumption using sales gas.
3) If the total cost (Capex) to convert the plant to burn sales gas instead of HFO is $41,000.
Calculate the Net Present Value from the fuel savings from 2022 till 2030 considering
the following fuel cost profiles:
Table 4: Scenario 1, No Change in Current Prices.
Year 2022 2023 2024 2025 2026 2027 2028 2029 2030
HFO
($/MMBTU)
0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6
Sales Gas
($/MMBTU)
1.25 1.25 1.25 1.25 1.25 1.25 1.25 1.25 1.25
Table 5: Scenario 2, HFO Price will be more expensive than gas going forward.
Year 2022 2023 2024 2025 2026 2027 2028 2029 2030
HFO
($/MMBTU)
0.6 0.9 1.2 2.1 4.0 5.6 7.4 8.9 9.8
Sales Gas
($/MMBTU)
1.25 1.25 1.25 1.25 1.25 1.25 1.25 1.25 1.25
21
Table 6: Conversion Factors.
Electric to Thermal
Conversion Factor
(MMBtu/MWh)
Thermal Energy
Per Barrel
(MMBtu/BBL)
Number of Hours
per year
Thermal Energy
Per Standard Cubic
Foot (MMBtu/SCF)
3.412 6.327 8760 1080
Table 7: Summary of Given Parameters
Unit
Parameter
A B C D
Capacity (MW) 300 300 800 800
Efficiency 25.00% 25.00% 35.00% 35.00%
Utilization Rate 90.00% 90.00% 90.00% 90.00%
Power Plant
Conversion Capex
$41,000
Annual Interest
Rate
6.00%
The solution to this problem can be approached by summarizing the information given in
the problem above in Table 7. First, to find the daily fuel consumption of HFO, required in
the first part of the problem, the unit of the capacity (MW) needs to be converted to the
unit of heat (MMBtu), and after that, by dividing by Thermal Energy Per Barrel, heat is
converted to Barrels of HFO (BBL). A step-by-step solution is provided next. The reader
is suggested to refer to Table 8 shown in the next page as he reads the following steps. To
calculate how much of the capacity has been utilized, the capacity of the power plant is
multiplied by the utilization rate (Step 1) to find the utilized energy. After that, to convert
the utilized energy into heat, while taking the efficiency into account, the utilized energy
22
is divided by the efficiency and, at the same time, multiplied by Electric to Thermal
Conversion Factor (Step 2), thus, resulting in the hourly heat utilized by the unit.
First, to find the number of barrels used for each unit, simply divide the hourly heat utilized
by the conversion factor Thermal Energy Per Barrel, and multiply the answer by 24 to
convert the hours to days (Step 3), since daily fuel consumption is required. Second, to find
the daily consumption of sales gas, as needed in part 2 of the problem, steps 1 and 2 must
be repeated to find the hourly heat utilized. Next, the hourly heat utilized is divided by the
conversion factor Thermal Energy per Standard Cubic Foot, and again, since sales gas is
required daily, the answer is also multiplied by 24 (Step 4). The answers to parts 1 and 2
of the problem are shown in Table 8. Third, to calculate the NPV of both scenarios, we
need to find the total yearly heat utilized. This is done by multiplying the total hourly heat
utilized found in step 2 by 8760, which is the number of hours in a year. After that, multiply
the price of HFO by the total yearly heat utilized to find the yearly cost of producing HFO.
Table 8: Steps to Find Daily Fuel Consumption of HFO and Sales Gas.
Steps Parameter A B C D Total
Step 1 Energy Capacity (MWh) 300 300 800 800 2,200
Utilized Energy (MWh) 270 270 720 720 1,980
Step 2 Hourly Heat Utilized
(MMBtu)
3,685 3,685 7,019 7,019 21,408
Step 3 Daily Barrels Needed (BBL) 13,978 13,978 26,625 26,625 81,206
Step 4 Daily Gas Needed (SCF) 82 82 156 156 476
23
Applying this reveals that the total cost of HFO, as based on scenario 1, is $112,519,727
dollars yearly, meaning that it does not change. Doing the same, that is multiplying the
total yearly heat required by the price of Sales gas, gives the yearly cost of producing Sales
Gas.
More importantly, if we were to convert the Rabigh Power Plant from HFO to Sales gas,
the first year will have only Capex cost, which is $41,000. The following years will be the
difference between HFO costs to Sales Gas costs, as will be shown later. For Scenario 1,
with unchanged HFO prices. The NPV is -$714,143,708. This means that Rabigh Power
Plant, if converted to Sales Gas, will cause a loss of more than 700 million dollars.
Table 9: Total Costs of Fuels in Scenario 1.
Scenario
1
Year
Total Cost
(HFO)
Total Cost
(Gas)
Differential
(Gain)
NPV
2022 $112,519,727 $234,416,098 -$41,000
-$714,143,708
2023 $112,519,727 $234,416,098 -$121,896,371
2024 $112,519,727 $234,416,098 -$121,896,371
2025 $112,519,727 $234,416,098 -$121,896,371
2026 $112,519,727 $234,416,098 -$121,896,371
2027 $112,519,727 $234,416,098 -$121,896,371
2028 $112,519,727 $234,416,098 -$121,896,371
2029 $112,519,727 $234,416,098 -$121,896,371
2030 $112,519,727 $234,416,098 -$121,896,371
24
However, as mentioned earlier in section 3 (Fuel mix in the kingdom), the government
plans to remove the subsidies from all liquid fuels, which for sure causes the price of HFO
to increase significantly. Scenario 2 anticipates the change of increasing the price of HFO.
Repeating the calculation done before with the expected HFO prices results in NPV to be
$3,636,575,644, that is, the profits of this project, if the price of HFO changed as expected,
will exceed three and a half billion dollars. This project will break even between the years
2024 to 2025, as shown in the table below.
Table 10: Total Costs of Fuels in Scenario 2.
Scenario
2
Year
Total Cost
(HFO)
Total Cost
(Gas)
Differential
(Gain)
NPV
2022 $112,519,727 $234,416,098 -$41,000
$3,636,575,644
2023 $168,779,591 $234,416,098 -$65,636,508
2024 $225,039,454 $234,416,098 -$9,376,644
2025 $393,819,045 $234,416,098 $159,402,947
2026 $750,131,515 $234,416,098 $515,715,416
2027 $1,050,184,120 $234,416,098 $815,768,022
2028 $1,387,743,302 $234,416,098 $1,153,327,204
2029 $1,669,042,620 $234,416,098 $1,434,626,522
2030 $1,837,822,211 $234,416,098 $1,603,406,112
It is important to note for the reader that this is a real project that is going to be done by
Aramco. The prices used here may not be as accurate as in their calculations, because real
25
data is considered government confidential, meaning that the author does not have access
to these data. However, real data are not far away from the numbers above based on what
Nassar, the supervisor of Kingdom Utilities division in Aramco, said.
2.3. Power Transmission
This section shows first the kingdom's gas network with the plan to expand it. It then covers
briefly classifications and types of transmission towers and poles. After that, it outlines
Saudi Arabian Grid Code, and dives deep to the operations and an agreement regarding the
grid. Finally, an exercise is solved to explain the usefulness of Transmission Use of System
agreement.
2.3.1 Current and Future Gas Network
Currently, the kingdom of Saudi Arabia depends on two types of fuels: Gas and Crude Oil.
These fuels are extracted from Earth in Oil fields. After extraction, fuels are sent to Oil
Facilities for the purpose of separating and removing impurities from fuels. Figure 8 in the
next page shows the different oil fields and oil facilities of the kingdom, in blue and green,
respectively. The facilities and fields of oil are all connected to Abqaiq facility, and from
there, fuels are transported via pipelines across Riyadh to finally reach Yanbu, as shown in
Figure 9 where they are represented as orange lines. At Yanbu, a 3100 MW power plant
utilizes transported fuel. Indeed, there are two pipelines, one pipeline with 56-inch in
diameter to transport oil, and the other is a 48-inch diameter to transport natural gas [18].
The kingdom plans to expand and install new pipelines running from Riyadh to Shuaiba.
The purpose of doing so is to utilize the largest power plant in Saudi Arabia, the Shuaiba
26
Power and Desalination Plant located in the south of Jeddah, with a total capacity of 5.6
GW [18]. The new pipeline is shown below in Figure 10.
Figure 8: Saudi Arabian Oil Fields and Oil Facilities [19]
Figure 9: Saudi Arabia’s Pipelines [18]
Riyadh
Yanbu
27
Figure 10: Saudi Arabia’s Shuaiba’s Pipeline.
2.3.2 Transmission Towers & Poles
After generating electricity in power plants, and after stepping up its voltage, overhead
transmission lines carry the electricity to industrial, commercial, or residential loads. Along
the way, Transmission Towers and the poles carry heavy conductors. These two are
categorized based on their voltage level, construction material, and finally number of lines
carried.
Based on Voltage, they can be classified as High Voltage, for more than 69 KV, medium
voltage, between 600 V to 69 KV, and low voltage, under 600V. Speaking about the
construction material, the standard material used in building transmission towers is steel,
due to its strength, lightweight, and most importantly, its inexpensive cost. If more
durability is needed, for example, in areas that experience seismic activities, then concrete
is used instead in building them. More durability comes with an increased costs because of
concrete price. While concrete poles and steel transmission towers are used to carry
Riyadh
Yanbu
Shuaiba
28
medium and high voltage lines, respectively, wooden transmission poles are used in low
voltage lines. This is mainly because of their low cost, ignoring their lack of strength and
durability. The mentioned types are shown in Figure 11.
Finally, when it comes to the number of lines carried, Transmission Towers can carry
cables that feed single circuits, double circuit, or multiple circuits. Single circuit
transmission towers carry low voltage transmission lines, double circuit carry medium
voltage, and multiple circuit carry high voltage conductors. The three types are shown in
Figure 12.
Figure 11: An Illustration of Different Electrical Towers and Poles [20].
29
Figure 12: Transmission Tower Classification Based on Supply Circuits [21].
A typical transmission tower consists of the following components:
1) Cross Arms: used to carry power lines.
2) Insulator: used to hold power lines in place, and keep them isolated from transmission
tower. Since transmission towers are conductive, any power line touching the
transmission tower will cause electricity to flow to earth, resulting in a ground fault.
3) Cable Raiser: used to raise the cables and keep them insulated from the tower.
4) Buss Bar: used to combine the energy from two cables into a single line.
5) Lightning Arrester: used to protect the transmission line and tower from lightning,
creating a path for excess electricity to flow directly to ground.
6) Skirts: Used to insulate the tower from the power cables. This is to increase the
protection on the cables from lighting. By increasing the resistance of the cable
insulation, the current coming from the lightning will be guided towards earth directly.
30
7) Guy Strain Insulator: This is to insulate the guy wire (a wire that is used to support
in holding transmission tower from leaning) from the transmission tower. All the
components are depicted in Figure 13.
Figure 13: Components of a Transmission Tower
31
2.3.3 Saudi Arabian Grid Code
To ensure a safe, reliable, and efficient operation of the grid, WERA created the SAGC
(Saudi Arabian Grid Code). SAGC is a technical regulatory document that defines the
obligations and responsibilities to the owner of the grid, that is SEC, and to all Users of the
grid. SAGC is written specifically for the generation and transmission parts of the power
system, while the Saudi Arabian Distribution Code, a document similar to SAGC, is
dedicated to the distribution stage. Within the SAGC, six major codes are discussed, which
are Connection Code, Planning Code, Operating Code, Metering Code, Data & Information
Exchange Code, and finally Scheduling and Dispatch Code.
All the above codes set the minimum requirement and rules that must be followed in order
to comply with SAGC. Before introducing the codes, it is better to start with the general
conditions, which connect and clarify any potential misconception with the above codes.
General Conditions contains provisions that are applied to all sections of the Grid Code.
Their main objective is to ensure that different sections of the Grid Code work collectively
and in harmony. General problems that Users may face are discussed in this section, for
example, when should a condition of the grid code be skipped, how to settle a dispute, and
etcetera.
Connection Code focuses on any connection related topics, connection agreements,
transmission system performance like frequency or voltage variations, operation, and
maintenance safety conditions…etc. The reader is suggested to refer to this section
whenever his needs are technical and related to the connections between the grid and Users.
Note that all plants and apparatus at the Connection Point shall comply with the relevant
32
TSP (Transmission Service Provider) standards, or in their absence, other IEC, ANSI, or
IEEE standards. The procedure to connect to the national grid is demonstrated in Figure
14.
Planning Code is intended for tasks that are related to the development and expansion of
the transmission system. It also specifies the data that should be exchanged between the
TSP and Users of grid. Planning, responsibilities, processes, and the grid information is
covered in detail in this section.
Operating code covers the topics that are related to proper operation of the Grid, for
example, energy demand forecasting, maintenance planning for electricity generation and
transmission, management of system support services, contacting between the TSP and
Users and coordination of Safety. Apart from this, to avoid blackouts, black start stations
are used, which are generators that start up whenever a power outage occurs to a city.
Methods of investigation and verification of performance are explained in this section.
Scheduling and Dispatch Code specifies the responsibilities and obligations of the TSP
and Users regarding scheduling and dispatching of generating units and demand resources.
Moreover, this code establishes a procedure for users to supply accurate information to
TSP. After that, the TSP prepares and issues Generation Schedules and Dispatch
Instructions.
Metering Code sets out the regulations and rules for metering and recording requirements
for Participants. In addition, it clarifies the obligations of the participants related to such
installations of meters. Furthermore, it also establishes important technical design and
operational criteria that grid participants shall comply with in terms of metering and data
collection of equipment and installations.
33
Figure 14: Procedure of Connecting to National Grid
34
2.3.4 Features of National Grid.
Large Companies, especially ones that produce electricity like Aramco, have a complex
relationship with SEC where they can use grid infrastructure for various operational
purposes. Their relation can be understood through three main ways: Spill mechanism,
wheeling strategy and security of supply. Each of these ways is explained below.
Spill Mechanism: When a company produces more energy than it needs, the company
sells the extra energy to PB. This excess energy is distributed to other users of the grid.
The price of this energy is typically much lower than the one purchased from PB, due to
the fact that PB is the only customer in the energy market who can purchase this energy,
as explained in section 2.1. Although the price of the sold excess energy is low, it is
considered a very good way to reduce surplus energy losses.
Wheeling Strategy: in this strategy, companies are allowed to transfer their excess energy
through the grid, enabling an efficient energy distribution across different parts of
companies’ outlets. Due to the fact that all cities of the kingdom are connected to the power
grid, the company will not face difficulties in transferring its excess energy even if its
energy generators are far away from its outlet, say, one in the eastern side of the kingdom
while the other is at the center. Companies can transfer their excess energy after signing
the Transmission Use of System agreement, explained in detail in the next section.
Security of Supply: This strategy serves to protect companies from power outages. To
explain, when companies’ energy resources are depleted, companies can directly utilize the
power supplied by the grid, preventing the stoppage of their operation. Demand meters are
employed to measure the amount of power that has been consumed from the grid, which is
used later in calculating electricity consumption invoice to be paid for PB.
35
2.3.5 TUoS Agreement
Transmission Use of System (TUoS) is an agreement that governs wheeling, that is the
transmission of excess power, from one facility to the other. To explain, worldwide oil and
gas companies, like Aramco, usually build power plants to generate their needed electricity,
since it is cheaper for them in the long run. However, some outlets of the company are not
directly connected to their generators, it is connected to company’s generators through the
grid, which are called off-site facilities, as shown in Figure 15.
Figure 15: Connection of Off-Site Facilities
Therefore, to feed energy to the off-site facilities, the company is bound between two
choices. First choice is to agree upon the TUoS agreement and pay its related taxes. The
second choice is to purchase electricity directly from PB. Assuming that the company
agrees upon TUoS Agreement, then it must pay the TUoS Payment and Bulk Supply
Charge (BSC), defined in (2.1) and (2.2). Otherwise, if the company would like to buy
electricity directly from PB, then it must pay PB invoice, given in (2.3). Note that the
average of demand peaks, shown in all three equations, is calculated using (2.4). In
addition, the load factor, as described in (2.5), is analogous to the efficiency of paid
36
electricity. For example, when a company pays an invoice with low load factor, say 10%
load factor, it means 100 MW was purchased, but only 10 MW is received.
𝑇𝑈𝑜𝑆 𝑃𝑎𝑦𝑚𝑒𝑛𝑡 (𝑆𝐴𝑅) = 𝑇𝑈𝑜𝑠 𝑃𝑟𝑖𝑐𝑒 (
𝑆𝐴𝑅
𝐾𝑊
) ×
𝐴𝑣𝑒𝑟𝑎𝑔𝑒 𝑜𝑓 3 𝑑𝑒𝑚𝑎𝑛𝑑 𝑝𝑒𝑎𝑘𝑠(𝐾𝑊)
𝐿𝑜𝑎𝑑 𝑓𝑎𝑐𝑡𝑜𝑟
(2.1)
𝐵𝑆𝐶(ℎℎ) = 𝐵𝑆𝐶 𝑡𝑎𝑟𝑟𝑖𝑓 (
ℎℎ
𝐾𝑊ℎ
) × 𝑌𝑒𝑎𝑟𝑙𝑦 ℎ𝑜𝑢𝑟𝑠(ℎ) × 𝐴𝑣𝑒𝑟𝑎𝑔𝑒 𝑜𝑓 3 𝑑𝑒𝑚𝑎𝑛𝑑 𝑝𝑒𝑎𝑘𝑠(𝐾𝑊) (2.2)
𝑃𝐵 𝐼𝑛𝑣𝑜𝑖𝑐𝑒(𝑆𝐴𝑅) = 𝑇𝑎𝑟𝑟𝑖𝑓 (
𝑆𝐴𝑅
𝐾𝑊ℎ
) × 𝑌𝑒𝑎𝑟𝑙𝑦 𝐻𝑜𝑢𝑟𝑠(ℎ) × 𝐴𝑣𝑒𝑟𝑎𝑔𝑒 𝑜𝑓 3 𝑑𝑒𝑚𝑎𝑛𝑑 𝑝𝑒𝑎𝑘𝑠 (𝐾𝑊) (2.3)
𝐴𝑣𝑒𝑟𝑎𝑔𝑒 𝑜𝑓 3 𝑑𝑒𝑚𝑎𝑛𝑑 𝑝𝑒𝑎𝑘𝑠 =
𝑃𝑒𝑎𝑘 1 + 𝑃𝑒𝑎𝑘 2 + 𝑃𝑒𝑎𝑘 3
3
× 𝑇𝑈𝑜𝑆 𝑃𝑟𝑖𝑐𝑒 (2.4)
% 𝐿𝑜𝑎𝑑 𝑓𝑎𝑐𝑡𝑜𝑟 =
𝐴𝑣𝑒𝑟𝑎𝑔𝑒 𝐿𝑜𝑎𝑑
𝑀𝑎𝑥𝑖𝑚𝑢𝑚 𝐿𝑜𝑎𝑑
× 100 (2.5)
2.3.6 TUoS Exercise
The problem Statement is: should a company purchase electricity directly from SEC, or
transfer the excess power from its generators? Given that the average power consumption
of the company is 100,000 KW, Current TUoS Price is 287.4 Sar/KW, and tariffs are as
given in SEC website.
The tables in the next page summarize the information needed to solve the problem. The
tariffs, as given by SEC, with other parameters are shown in Tables 11 and 12, respectively.
The cost of purchasing power directly from SEC for all types of loads is found using (2.3).
Results are shown on Table 13.
37
Table 11: Tariffs of Different End-users
Table 12: Given Parameters
Table 13: Cost of Purchased Energy per Load Type
Now, to find the price for wheeling the excess power, the Bulk Supply Charge must be
calculated first using (2.2).
𝐵𝑆𝐶(𝑆𝐴𝑅) = (8.3)/100 ∗ (24 ∗ 365) ∗ (100000)
End-User Tariffs (hh/KWh)
Residential 30
Commercial 30
Agricultural 20
Governmental 32
Industrial 18
Private Education
Facilities
18
Avg of Demand
Peaks
100000 KW
TUoS Price 287.4 SAR/KW
Bulk Supply Tariff 8.3 hh/KWh
Yearly Hours 8760 h
End-User Energy Cost Purchased (SAR)
Residential $262,800,000
Commercial $262,800,000
Agricultural $175,200,000
Governmental $280,320,000
Industrial $157,680,000
Private Education Facilities $157,680,000
Table 11: Tariffs of Different End-users Table 12: Given Parameters
Avg of Demand
Peaks
100000 KW
TUoS Price 287.4 SAR/KW
Bulk Supply Tariff 8.3 hh/KWh
Yearly Hours 8760 h
Table 12: Given Parameters
38
Resulting in
𝐵𝑆𝐶 = 72,708,000 𝑆𝑎𝑟
Next to find the TUoS Payment, (2.1) is used. Different arbitrary load factors are assumed.
Therefore, we have the following results shown in Table 14. Adding Table 14 to the Bulk
Supply Charge gives the total costs for transferring energy, shown in Table 15. Finally, a
comparison between the costs of purchasing electricity from SEC and transferring excess
energy is shown in the next page, Table 16, where simply the green number stands for
revenues, and, conversely, red number is for losses.
Table 14: TUoS Payment with Different Load Factors
Table 15: Total Cost of Transferred Energy
Load Factor TUoS Payment (SAR) Bulk Supply
Charge
Load Factor TUoS Total
Cost (SAR)
100.00% $28,740,000
$72,708,000
100.00% $101,448,000
95.00% $30,252,632 95.00% $102,960,632
90.00% $31,933,333 90.00% $104,641,333
85.00% $33,811,765 85.00% $106,519,765
80.00% $35,925,000 80.00% $108,633,000
75.00% $38,320,000 75.00% $111,028,000
70.00% $41,057,143 70.00% $113,765,143
65.00% $44,215,385 65.00% $116,923,385
60.00% $47,900,000 60.00% $120,608,000
55.00% $52,254,545 55.00% $124,962,545
50.00% $57,480,000 50.00% $130,188,000
45.00% $63,866,667 45.00% $136,574,667
40.00% $71,850,000 40.00% $144,558,000
35.00% $82,114,286 35.00% $154,822,286
30.00% $95,800,000 30.00% $168,508,000
25.00% $114,960,000 25.00% $187,668,000
20.00% $143,700,000 20.00% $216,408,000
15.00% $191,600,000 15.00% $264,308,000
10.00% $287,400,000 10.00% $360,108,000
5.00% $574,800,000 5.00% $647,508,000
Table 14: TUoS Payment with Different
Load Factors
Table 14: TUoS Payment with Different
Load Factors
Table 15: Total Cost of Transferred
Energy
Table 15: Total Cost of Transferred
Energy
39
Table 16: Cost Comparison (Purchased Energy – Transferred Energy).
Load
Factor
Residential Commercial Agricultural Governmental Industrial
Private
Education
Facilities
100.00% $161,352,000 $161,352,000 $73,752,000 $178,872,000 $56,232,000 $56,232,000
95.00% $159,839,368 $159,839,368 $72,239,368 $177,359,368 $54,719,368 $54,719,368
90.00% $158,158,667 $158,158,667 $70,558,667 $175,678,667 $53,038,667 $53,038,667
85.00% $156,280,235 $156,280,235 $68,680,235 $173,800,235 $51,160,235 $51,160,235
80.00% $154,167,000 $154,167,000 $66,567,000 $171,687,000 $49,047,000 $49,047,000
75.00% $151,772,000 $151,772,000 $64,172,000 $169,292,000 $46,652,000 $46,652,000
70.00% $149,034,857 $149,034,857 $61,434,857 $166,554,857 $43,914,857 $43,914,857
65.00% $145,876,615 $145,876,615 $58,276,615 $163,396,615 $40,756,615 $40,756,615
60.00% $142,192,000 $142,192,000 $54,592,000 $159,712,000 $37,072,000 $37,072,000
55.00% $137,837,455 $137,837,455 $50,237,455 $155,357,455 $32,717,455 $32,717,455
50.00% $132,612,000 $132,612,000 $45,012,000 $150,132,000 $27,492,000 $27,492,000
45.00% $126,225,333 $126,225,333 $38,625,333 $143,745,333 $21,105,333 $21,105,333
40.00% $118,242,000 $118,242,000 $30,642,000 $135,762,000 $13,122,000 $13,122,000
35.00% $107,977,714 $107,977,714 $20,377,714 $125,497,714 $2,857,714 $2,857,714
30.00% $94,292,000 $94,292,000 $6,692,000 $111,812,000 -$10,828,000 -$10,828,000
25.00% $75,132,000 $75,132,000 -$12,468,000 $92,652,000 -$29,988,000 -$29,988,000
20.00% $46,392,000 $46,392,000 -$41,208,000 $63,912,000 -$58,728,000 -$58,728,000
15.00% -$1,508,000 -$1,508,000 -$89,108,000 $16,012,000 -$106,628,000 -$106,628,000
10.00% -$97,308,000 -$97,308,000 -$184,908,000 -$79,788,000 -$202,428,000 -$202,428,000
5.00% -$384,708,000 -$384,708,000 -$472,308,000 -$367,188,000 -$489,828,000 -$489,828,000
Hence, based on the load factor, the company’s decision is taken. If we were to assume
that the load is residential, and its load factor is more than 15.12%, then for sure it would
be better to transfer excess power. If not, then buy it from PB.
40
2.4. Power Distribution
This section goes over some of the technology activities done in the POD department. It
starts with a detailed view of the UPS system, mentioning details about what it is, what are
its types and applications, and then dives deeply to the On-Line Double Conversion UPS
system by laying down its main application, process, components, and maintenance
activities. Followingly, the same is done in power transformer in terms of showing its types,
components and maintenance tests. It then outlines key information about low voltage
breakers and finally gives a summary about protective relays, needed to understand Chapter
3.
2.4.1 Uninterruptible power supply
An Uninterruptible power supply (UPS) is an apparatus used to maintain energy supply to
loads, commonly in the case of a power outage. UPS Systems can be classified based on
four main factors. Battery Capacity, to determine capability to supply the load. Power
Conditioning, in which voltage supply is cleaned from fluctuation. Transfer time, the time
it takes to transfer from primary supply to the battery. And finally Surge Protection, the
technology used to protect the equipment from, for example, overloading and lighting.
Based on these specifications, the three types of UPS systems are classified which are:
Standby UPS system, Line-interactive UPS system, and Online Double Conversion UPS
system.
Three types of UPS System exist. First, the most basic form is the Standby UPS system.
Simply, it uses AC power supply, and when a power outage occurs, the load receives
energy from UPS’s battery. It does not have the Power Conditioning feature. However, it
41
can supply energy to small devices, specifically, ones with under 600 VA [22]
consumption, e.g., printers, scanners, routers and other home or office devices. In addition,
it takes 2-10 ms [22] to transfer the load, which means it is not a good option for critical
loads, personal computers for example.
Second, the line-interactive UPS system has the Power Conditioning feature; a built-in
transformer is employed to decrease voltage fluctuations. Besides, it has a battery capacity
that reaches up to 5 KVA [22]. The transfer time of the line-interactive UPS system is
between 2 to 4 milliseconds, enough for critical loads.
Finally, and most importantly, is the Online Double Conversion UPS System. The capacity
of the batteries depends on user’s need. As will be shown later, the batteries for Aramco’s
data centers reaches up to a 100 KVA, with a Transfer time less than 4 milliseconds [22].
Several layers of electronic components, filters and surge protectors, are used in removing
electrical disturbances. It is important to note that any commercial UPS system must meet
the following requirements [23] [24]:
1) It must have a constant steady state RMS voltage, with less than 2% variation in other
parameters, e.g., load current.
2) No more than 10% peak transient voltage deviation is allowed in loading/unloading
process.
3) The inverter output voltage shall not have more than 4% total harmonic distortion in
all load conditions.
4) In 2 AC cycles, the voltage must not drop more than 5% of the rated voltage.
42
Next, the process of a UPS system is as follows, electricity is supplied and converted to
DC using the rectifier. It is then converted back to a clean sinusoidal AC by the inverter.
This is done to (1) isolate the load from frequency variation, (2) to clean voltage distortions
before it is supplied, as critical loads are sensitive to these distortions, and (3) charge the
batteries, since they cannot be charged with AC. The components of the Online Double
Conversion UPS system are shown in Figure 16.
Figure 16: Equipment of Online Double Conversion UPS System [25]
UPS is operated in one of the three modes, namely, normal mode, bypass mode, and battery
mode. Firstly, in normal mode, the UPS will operate as mentioned in the previous
paragraph. It isolates the load and supplies it with clean sinusoid electricity. Secondly,
bypass mode is activated when any fault occurs inside the UPS system. The transfer switch
connects the load to the main supply directly through bypass line until the internal fault is
fixed. Finally, any interruption to the primary power supply results in an automatic
conversion to battery mode. In this mode, batteries feed the critical load through inverter.
Whenever batteries’ energy is depleted, the UPS will check the status of Bypass line. If
there is energy on the bypass, UPS will switch to the bypass line using the transfer switch.
43
Otherwise, UPS will issue a shutdown Imminent alarm. In case the AC power supply is
back, UPS mode is switched back to the normal mode. Additionally, UPS consists of
batteries, transfer switches, solid-state rectifier, and an inverter. Each of these components
is discussed and depicted in the next several pages.
1) Batteries
Lead-acid batteries are used in the UPS System due to their low cost, long lifespan ranging
from 6 to 15 years [26], and reliable performance. Each package of Lead-acid batteries is
connected in series to increase its total output voltage. Each battery, shown next page in
Figure 17 is a 2.2 Volt battery, collectively having an output voltage of 240V. Each package
of batteries is connected in parallel to increase their capacity. Utilizing all the packages,
the UPS system has an output capacity of 100 KVA [27], with 0.9 Power factor.
2) Transfer Switch
Transfer switch is an auto/manual switch to change UPS’s mode of operation, shown in
Figure 18. For maintenance, specifically in minor preventive maintenance, the transfer
switch is used to convert supply directly through the Bypass. However, in Major Preventive
Maintenance, the isolation switch is used to shut down the UPS completely.
3) Rectifier
Rectifier is used for two purposes, (1) to convert AC voltage into DC, and (2) to smooth
and clear noise and spikes from voltage supply. Rectifier’s equipment are shown in the
Figure 19. Control Fuses are used to protect the fans from faults, and Input Fuses protect
44
the Input Capacitors. Input Capacitors aid in smoothing input voltage. Rectifier’s Blower
Fans cool down the rectifier, and the DC capacitors cleans output DC signal from
distortions. Breaker is used to shutdown the rectifier when internal fault occures.
4) Inverter
Inverter converts DC Voltage into AC. Its equipment are shown in Figure 20. The Remote
Communcation Board is for communcating with an outside computer. The internal
communcation board is for internal communcation between components of the Inverter.
Figure 17: Batteries of the UPS System.
45
Figure 18: Representation of Transfer Switches
46
Figure 19: A Photograph of UPS Rectifier
47
Figure 20: Illustration of a UPS Inverter
48
The main application of a UPS system is elucidated in the following case. Whenever the
input supply fails, critical loads receive energy from UPS. Servers of companies are a very
good example of this. To elucidate the usefulness of using UPS system, assume the
following case. When company servers are detached from electricity, all unsaved
information is lost. In addition, all services within the company are discontinued. A
disconnection time of 9ms may shutdown company’s servers. To prevent this problem,
UPS system is installed for backup energy. Moreover, Alrashdi, foreman of the UPS unit
in Power Operation Department, specified in a personal interview that batteries of the
Online UPS system can supply energy to the Tower building of Aramco, a building with
an average energy consumption of around 200 KWh, for possibly 30 minutes. At that time,
another simple cycle generator is prepared to start supplying energy to the tower.
Now with the maintenance activities. Technicians apply three types of maintenance:
Inspection, Minor PM (Preventive maintenance), and Major PM. In Inspection, technicians
visually inspect the UPS from outside, i.e., verify status screen of the UPS system. They
also measure the voltage of 10% of the batteries of the UPS system. In other words,
technicians measure at least three batteries for each battery package. The inspection is done
on a weekly basis.
In Minor PM, first, technicians measure the voltage and current of (1) receiving end of
Inverter, (2) primary supply, and (3) measure all 24 batteries, of one package, and compare
them to their normal operation case. Second, technicians visually check internal
components of the UPS. Third, technicians use a thermo vision tool to inspect physical
integrity of voltage supply cables, output feeders and ground connections. Finally,
49
technicians clean the filters of the UPS using air extractors. The Minor PM is done on
quarterly basis.
In Major PM, the above activities are all also completed. But before that, UPS System must
be shut downed completely. In addition to the Minor PM activities, technicians examine
the UPS capacitors, namely, Input and DC Capacitors, and replace them in case of any
damage or leakage exists. More importantly, in Major PM, technicians test the control
circuitry (the PCBs), and at the end, simulate an emergency case to verify the readiness of
the UPS.
2.4.2 Power Transformer
Power Transformer is a 3-phase, Delta – Y connected, bulky passive electromagnetic
device used for HV (High Voltage) conversion, i.e., above 69 kV. The Power Transformer
steps up or down HV, and is mainly used in power plants to decrease the current, thus,
decrease the losses through transmission lines. One feature of Power transformer is its tap
changer, to change the turn ratio by changing the tap of the secondary winding. Speaking
about the components, Power Transformer consists of 13 components, shown partially
inside Aramco’s workshop in Figures 21 and 22, and collectively in Figures 23 and 24.
These are:
1) Main Tank, which contains insulated windings of the primary and secondary sides.
2) HV Bushing, similar to the suspension insulators, except that from inside, it contains
a conductor, protected by an insulating material, to guard the HV cables feeding the
Power Transformer.
3) LV (Low Voltage) Bushings, connected to the LV side of the transformer.
50
4) Radiator, used in dissipating the heat of the transformer.
5) Cooling fans, operated automatically by a Temperature Relay.
6) Conservator Tank, used to store excess oil from the Main Tank, because when the
temperature of the transformer increases, the oil within the Main Tank expands and
leaks. Thus, leaked oil is collected by the Conservator Tank
7) Ground Terminal, connected commonly to NGR (Neutral Ground Resistor), an
enormous resistor used to dissipate electrical surges coming from, say, lightning.
8) Drain Valve, opened to let the oil flow out of the transformer. It is used for two reasons:
(1) To take a sample for measuring multiple factors of the oil, insulation capability for
example, and (2) to drain the oil tank when oil replacement is needed.
9) Dehydrating Breather, shown in Figure 24, is used to prevent moisture from entering
the oil tanks of the transformer.
10) Oil Temperature and Pressure Gauges, measure and display temperature and
pressure, in degrees Celsius and in kilo pascals, respectively.
11) Bushing Current Transformer, used to measure the current flowing through the
winding, which is attached to the control panel for monitoring purpose.
12) Control Panel, where operations of the transformer are monitored and controlled both
manually and automatically.
13) Tap changer, not shown in figures, used to change the turn ratio, ratio of turns between
primary winding and secondary winding.
51
Figure 21: Left View of a Power Transformer
Figure 22: Front View of a Power Transformer
52
Figure 23: Power Transformer Components [28].
Figure 24: Dehydrating Breather of Power Transformer [29].
53
Seven tests are applied to examine the performance of a Power Transformer. The purpose,
method and expected results of the tests are discussed below.
Insulation Resistance Test: This test measures insulation resistance of the oil around
transformer’s winding. The bigger the resistance, the better the insulation. To perform the
test, technicians connect an ohm meter as shown in Figure 25. Practically, the 3 HV
bushings are shorted, and the 3 terminals of LV Buss Bar inside the transformer are also
shorted. The positive terminal of Megger Insulation Tester is connected to the HV
bushings, while the negative terminal is connected to the LV Buss Bar. Any value bigger
than 1 Giga ohm is enough for passing the test. Failing in this test means the oil does not
provide adequate insulation between the primary and secondary windings.
It is worth noting that insulation insulates magnetic field based on its frequency. A low
frequency magnetic field is not attenuated by oil insulation. However, a high frequency
magnetic field is attenuated. That is why oil in transformers does not insulate the magnetic
field of the windings from each other, and at the same time, does not create a short circuit
between them.
Turn Ratio Test: This test examines the voltage of different taps of the transformer. It is
then compared to transformer’s nameplate. To perform the test, 10 KV is supplied to
primary side of the transformer through HV bushings, while the stepped down voltage is
measured from LV Buss Bar. The results are then scaled and compared to the nameplate.
The taps are considered in good condition only if the percentage difference between
nameplate and current measurement does not exceed 5%.
54
Figure 25: Connection of Insulation Resistance Test [30]
Winding Resistance Test: Opposite to the insulation resistance test, this test measures the
conductivity of the winding. Winding Resistance Test is performed though measuring the
resistance of all 6 windings, since Power Transformer is a 3-phase device. Less resistance
of winding means better conduction. Typically, the resistance of the winding is less than
20 mΩ. Result of this test can indicate if any cut in the winding wire exists.
Bushing Test: This test evaluates the physical integrity of the bushings. This test is carried
out by connecting the positive terminal of M7100, to the primary capacitor (Upward part
of the bushing) and negative terminal of the device to the ground. Repeated for phases
A,B,C. and then positive side of M7100 to secondary capacitor (Downward part of the
bushing) and negative side to the ground. Repeated for phases A,B,C. The transformer
condition is considered good only if the power factor of the bushing is less than 0.5%.
55
Surge Arrester Test: This test measures the insulation strength of surge arresters. This is
done by providing 50% of rated voltage of the arrester, and measuring the current that
flows through the arrester. The test must be carried out with consistency. For that reason,
technicians apply the same test voltage for the same amount each time, optimally 60
seconds. This test is repeated 3 times. The average reading is taken as the result. A
repeatable result is indicative of a good measurement process.
Sweep Frequency Response Analysis Test (SFRA): SFRA assesses the mechanical
integrity of transformer’s components, the core and winding for example. This test is
performed by sending signals of different discrete frequencies to the winding, and
measuring the returning signal. Results are graphed and compared to the older results. A
difference between the current and old results means a component has been displaced.
Example of SFRA graphical result is shown below in Figure 26, with a curve for each
phase of a transformer.
Figure 26: Example of an SFRA Test Measurement [31]
56
Oil Analysis Test: This is a diagnostic test to determine the condition of transformer oil.
A sample is taken via Drain Valve, and is sent to the laboratory for analysis. Various
parameters are analyzed, including oxidation stability, thermal stability, viscosity,
conductivity, acidity, color, moisture content, etc. measurement of these parameters may
reveal the causes of common problems in the Power Transformer, overheating and arcing
for instance.
2.4.3 Low Voltage Breakers
To provide control and protection for different large equipment, like generators,
transformers or motors, circuit breakers are used as a safeguard to defend personnel and
equipment from abnormal conditions. Circuit breakers control the flow of current, by
interrupting the circuit when extreme current is reached.
There are three main types of low voltage breakers that are used in industrial, commercial,
and residential buildings, which are: Miniature Circuit Breakers (MCBs), Molded Case
Circuit Breakers (MCCBs), and Residual Current Circuit Breakers (RCCBs). MCB are
widely used in residential and commercial constructions. They are compact devices
designed to safeguard electrical circuits from short circuits or overloads. The M (Miniature)
means the breaker is smaller than the other breaker types. MCCBs, on the other hand, are
a more robust version of MCBs. MCCBs can endure a greater amount of current, and are
commonly found in industrial and large-scale facilities. The MC (Molded Case) refers to
the breaker’s components being housed inside a highly durable and insulating casing,
preventing the current from leaking. Finally, RCCBs, sometimes referred to as Ground
Fault Circuit Breakers (GFCI), detect imbalances between live and neutral currents. They
are specialized in guarding against ground faults. RCCBs are typically found in houses,
57
specifically, inside breaker panels. The three breaker types are shown in Figure 27.
Typically, MCB is combined with RCB in practical applications, such as the one in Figure
28, where the main switch is an MCB.
Figure 27: An illustration of MCB, MCCB and RCCB, respectively (raw
image sources: [32][33][34]).
Figure 28: A Photograph of a Breaker Panel [35].
58
2.4.4 Protective Relays
To ensure safety and reliability, protection relays are used to shield personnel and
equipment from hazardous damage, caused by uncontrolled short circuits. The main
function of a protective relay is to operate the trip circuit quickly, specifically in the fault
area, while the rest of the system stays unaffected. Protective relays are most likely
installed within a switchgear, to detect abnormal conditions and activate its breakers.
Protection relays are characterized by four requirements, which are: Discrimination,
Coordination, Reliability and Speed of Operation. First, Discrimination is the relay’s
ability to discriminate between a normal overload, as what happens in noon when the
weather is too hot, to a heavy overload, caused for example by faults. Second, Coordination
is relay’s ability to be selective, that is, the relay only disconnects the output feeder having
the fault, without affecting input feeders. The reader can better understand this by referring
to Figure 29, where white boxes represent closed breakers, and red ones represent open
breakers.
Figure 29: An Illustration of Coordination Characteristic.
59
Thirdly, Reliability is the probability of a relay to work with no failure. Good practices in
manufacturing the relays heavily contribute to reliability. Also, regular maintenance and
excellent design reduce the probability of failure. Finally, Speed of Operation must be
rapid. As will be shown later in the second case study, electromagnetic relay is able to trip
the circuit in less than quarter of a second. This is essential to avoid injuries to personnel,
as well as damaging equipment.
ANSI Standard Device Number is used in naming the different types of relays. A number
is assigned to each type of relay. This is to simplify the one-line diagram by saving space
and text. Modern electronic protective relays may have multiple ANSI numbers when they
have multiple functions. The ANSI Standard Device Number is shown in Figures 30 and
31. The most common types of relays are demonstrated in Table 17, with their main
application.
60
Figure 30: First Page of ANSI Standard Device Number [36].
61
Figure 31: Second Page of ANSI Standard Device Number [36].
62
Table 17: Most Common ANSI Device Numbers
ANSI Number Application ANSI Number Application
25
Synchronizing
and
Synchronism-
check Device
After synchronizing its voltage
and frequency, the device
closes a breaker that connect a
generator to a live bus.
51
AC Time
Overcurrent
Relay
This relay trips when a
predetermined time and current
has been reached. The time
setting can be definite, that is,
no matter whether 1 A flowed
in the relay or 10A, the tripping
time remains the same.
Conversely, an inverse time
setting can be used to decrease
the trip time as the current
increases.
27
Undervoltage
Relay
Monitor the voltage of an
electrical system. The relay can
either energize alarm or trip the
circuit in the case of an
undervoltage.
52
AC Circuit
Breaker
A breaker that is controlled by
relays
32
Directional
Relay
Monitor the direction of
current. In DC circuit, the relay
trips after exceeding a certain
level of reverse polarity.
However, in AC circuits, the
relay trips based on the power
factor of the load, for example,
when a severe lagging power
factor is detected.
59
Overvoltage
Relay
Overvoltage relay has a similar
function to overcurrent relays.
This relay is designed to trip in
the case of overvoltage spikes.
40
Loss of Field
Relay
Observe the excitation level of
a generator using a coil, which
is connected in series with
generator field, and trips when
the field drop beyond setpoint.
64
Ground
Detector Relay
This relay functions on the
failure of insulation of, e.g., in
transformers, machines or other
apparatus. In other words, the
relay will operate when the
surface of an insulator becomes
conductive, causing a ground
fault.
50
Instantaneous
Overcurrent
Relay
Upon excessive current, or on
excessive rate of rise in current,
is reached, the overcurrent
relay will trip the associated
breaker instantly.
63
The remaining subject will summarize the details of the Electromagnetic relays. This is
done for the reader to be able to understand the case study discussed in Chapter 3.
Electromechanical relays are categorized by their use to one of two basic operating
mechanisms, which are: Electromagnetic attraction relays, and Electromagnetic induction
relays. An electromagnetic attraction relay is an electromagnet made from solenoid. This
type of relay is usually operated to activate the trip circuit inside a breaker. The other type
of electromagnetic attraction relay is a one that attracts hinged armature, to open or close
a set of contacts. Both types of electromagnetic attraction relay are identified by number
50, based on ANSI numbering system. These electromagnetic relays are instantaneous
pick-up, meaning that they do not have the time delay feature. They can work for both DC
and AC.
The instantaneous relay setting is adjustable, allowing user to regulate the amount of
current at which the relay picks-up. In a switchgear’s protection relay, this value is set
precisely. In case the monitored current is smaller than 4A, or higher than 144 A, a current
transformer is used to change the value of current to something within that current range.
The instantaneous relay tap settings are shown in Figure 32-D. The tap plug can be moved
to choose the range of current, while the screw is for precise calibration.
Induction relay, which is the second type of electromagnetic relays, operates like an
induction motor. The moving element, called metal disk, rotates on a shaft, as shown in
Figure 32-B, while the stationary coil senses the overcurrent or fault current. The induction
relay provides the time delay feature, which can be a definite-time or inverse-time type, as
clarified in Table 18, ANSI #51.
64
When the station coil is energized, current is induced to the metal disk to make it turn
against restraining spring to provide the time delay trip. The movable contact moves toward
the stationary contact at a speed proportional to the current flow in the coil. When the two
contacts touch each other, the auxiliary trip coil or breaker trip coil is energized.
Multiple coils can be used to vary the induction relay’s sensitivity to voltage and current.
The coil can be additive, or subtractive, that is they work together, or against each other.
Induction relays have very accurate pickup and time current response, as explained next in
Chapter 3.
65
4
A B
C D
Figure 32: Components of a CO-9 Electromagnetic Relay
A
A
B
B
C
C
D
D
66
CHAPTER 3: CASE STUDY I - ELECTROMAGNETIC
RELAY TEST
3.1. Introduction
On 17th
of March, an unexpected power outage occurred to a facility. The power meter was
reviewed, and no sudden current was found. However, it was expected later that the CO-9
Electromagnetic Relay installed in the protection system was the cause of this issue. For
this reason, the CO-9 Electromagnetic Relay was taken to the laboratory to be tested.
Therefore, this case study examines the healthiness of the CO-9 Electromagnetic Relay.
3.2. Methodology
A quantitative methodology was employed in this case study; it is to test the three main
parts of a CO-9 Electromagnetic Relay, namely, Instantaneous Relay Coil, Time Dial, and
the Current Tap Settings, which are shown in Figure 32-D, Figure 32-A and Figure 32-C,
respectively. This test is done by varying the three parameters separately, and comparing
the results to the characteristic curve of the CO-9 Electromagnetic Relay, shown in Figure
33.
In the figure, the x-axis shows the Multiples of Tap Value Current (MTVC), that is, the
ratio between testing current, injected to test the equipment, to the Current Tap Settings,
which is the current threshold. For instance, with 2A of current threshold, an injection
current of 4A results in MTVC to be 2. On the y-axis is the trip time. The more MTVC is
injected, the less time it takes the relay to trip. The tripping action will start only if the
MTVC is larger than 1.5. The series of trendlines shown in the figure are dependent on
Time Dial, or in other words, the time delay. The reader can notice that these series of
trendlines are only shifted versions of each other.
67
Figure 33: CO-9 Magnetic Relay Characteristic Curve [37]
Megger SVERKER 750, a relay test unit, was used to examine the electromagnetic relay.
This testing equipment is shown in Figure 34. Also, the connections of SVERKER 750 to
the electromagnetic Relay is depicted, separately, in Figures 35 and 36, respectively. It is
worth noting that the connection is the same for all the three tests.
68
Figure 34: A Photograph of the Megger SVERKER 750 [38]
Figure 35: Connection of SVERKER 750
Figure 36: Connection of CO-9 Relay
Figure 35: Connection of SVERKER 750
Figure 35: Connection of SVERKER 750
Figure 36: Connection of CO-9 Relay
Figure 36: Connection of CO-9 Relay
69
3.3. Findings
After injecting current and varying the Time Dial, the following results were obtained.
Injected
Current
Multiples
(MTVC)
Time Delay
(s)
Current
Threshold
(A)
Ideal Trip
Time (s)
Practical
Trip Time
(s)
% Error
x2
1
1
1.4 1.434 2.43%
2 2.7 2.811 4.11%
3 4 4.237 5.93%
4 5.7 5.674 0.46%
5 7 7.188 2.69%
Table 18: Results of Time Dial Test
Next, the Instantaneous Relay Coil setting was tested, and the results were as demonstrated
in Table 19.
Injected
Current
Multiples
(MTVC)
Time Delay
(s)
Current
Threshold
(A)
Ideal Trip
Time (s)
Practical
Trip Time
(s)
% Error
x2
1 1
1.4 1.474 5.29%
x3 0.6 0.613 2.17%
x4 0.35 0.371 6.00%
x5 0.25 0.276 10.40%
x6 0.2 0.238 19.00%
Table 19: Results of Instantaneous Relay Coil Test
Finally, the Current Tap Settings were tested, and the results were as found in Table 20.
Injected
Current
Multiples
(MTVC)
Time Delay
(s)
Current
Threshold
(A)
Ideal Trip
Time (s)
Practical
Trip Time
(s)
% Error
x2 1
1 1.4 1.409 0.64%
2 1.4 1.417 1.21%
3 1.4 1.396 0.29%
4 1.4 1.358 3.00%
5 1.4 1.313 6.21%
6 1.4 1.281 8.50%
Table 20: Results of Current Tap Setting Test
70
3.4. Analysis
In order for the CO-9 Electromagnetic Relay to pass the test, it must score an error
percentage below 5%. Failing to do so indicates that the equipment is faulty. Furthermore,
on average, the error percentages of the CO-9 Relay’s for the following components,
namely, the Time Dial, Instantaneous Relay Coil and Current Threshold, were 3.12%,
8.57% and 3.31%, respectively.
Upon examining the measured results, it becomes evident that our initial expectation about
corruption of CO-9 Electromagnetic Relay was valid. The Instantaneous Relay Coil was
not working as anticipated. The Error percentage was escalating significantly as MTVC
increases. Moreover, for the Current Tap Settings test, the trip time is supposed to remain
constant as the current threshold increases. However, the obtained results indicate that the
tripping time was inexplicably decreasing. Collectively, the abnormal function of the two
components could be the reason for the power outage issue.
3.5. Conclusion
The CO-9 Electromagnetic Relay failed the test. The two components, namely, Time Dial
and Instantaneous Relay Coil were not functioning as expected, with the latter exceeding
the limit of %Error. The following recommendations were proposed:
1) Conduct an inspection to all the protection relays that are installed within the same
switchgear.
2) In case any relay is tested and proven to be corrupted, replace immediately.
71
CHAPTER 4: CASE STUDY II - POWER OUTAGE IN
POD
4.1. Introduction
The central issue of this case study is to analyze the power outages in the POD department
taking place on the 2nd
and 3rd
of January 2023. A qualitative approach was followed in
this case study; it is to inspect for defective equipment in the area fed by the tripped breaker.
This case study will investigate, analyze and establish solution for the causes of the power
outage occurred to the POD.
4.2. First Case
At 3:46 PM, 2nd
of January, the Air Circuit Breaker feeding the 13.8 kV overhead line, and
eventually feeding POD buildings, was tripped by a neutral time overcurrent relay. Power
was restored after 26 minutes by closing the tie breaker, a breaker that is closed only to
supply energy from a secondary (emergency) source. The bus feeding the POD area was
sectionalized in order to troubleshoot and find the source of the electric fault. After
investigation, a spark was noticed on the insulator, located on a wooden electric pole. The
defective insulator was replaced, and the power was restored.
4.3. Second Case
The day after, on the 3rd
of January, at 11:41 AM, the Air Circuit Breaker feeding POD
buildings was tripped again by the overcurrent relay. Power was restored after 6 minutes.
The bus was sectionalized, and the troubleshooting process started. This time, a blown
surge arrester was found on the same wooden electric pole. The pole was isolated, and the
surge arrester was replaced, and finally the power was back to normal.
72
4.4. Analysis
For the first case, due to the rainy and windy weather conditions, the behavior of the
porcelain insulator overturned, causing a leakage current to flow through the insulator
surface. To explicate, when the insulator current encounters water, it generates heat that
increases water’s temperature. This rise in temperature causes a localized area to be dry,
forming what is called a dry band. Because of this dry band, high voltage electrons jump
through the dry band, seen in the form of a spark, as depicted in Figure 38. These sparks,
commonly known as arc discharges, damage the insulator and cause eventually a failure to
it. Upon the failure of the insulator, a chain reaction is triggered, progressing to pollution
flashover. During this phenomenon, the electrical stress exceeds the insulator’s ability to
resist it, leading to a breakdown of the insulator, and afterwards activating the main breaker
to trip and prevent further damage on the system. This process is summarized in Figure 37.
Figure 37: Pollution Flashover Progression of insulators [39].
73
Figure 38: The Process of Contamination Discharge on Polluted Insulators
[40].
Weather was not the only cause of the breaker trip. Further investigation revealed that the
damaged insulator had only 432 mm of creepage distance, which does not comply with
Saudi Aramco standard. According to Aramco’s standard, for each 1 KV, the insulator
must have at least 40 mm creepage distance. In other words, for a 13.8 KV line, it must
have a minimum of 552 mm creepage distance.
Regarding the second case, after investigation, the surge arrester meets the IEC 99-4
standard, having specifications of 10 KA peak current, 12 KV continuous voltage, 15 KV
residual voltage and with a hypered air-dielectric construction. In addition, the NGR
74
(Neutral Ground Resistor) was properly sized, with a rating of 1000 A, and therefore NGR
was not the reason for failure. The reason for the failure is probably due to the improper
grounding of the surge arrester, causing the current to circulate and eventually blow up the
surge arrester.
Moreover, the tripping of the main breaker feeding the POD area, instead of the one that
feeds the zone of the blown surge arrester was investigated. It was found later that there
were incorrect settings in the ground relay. The settings were corrected, and the case was
closed.
4.5. Conclusion
In this case study, an investigation was carried out to find the root causes of the power
outage that occurred in the Power Operation Department (POD). The causes of the issue
were due to a burned insulator, followed by a burned surge arrester. The two components
were replaced, and suggestions and recommendations were made to avoid future trips of
the main breaker. The following recommendations were suggested in this case study.
1) Immediately replace the defective insulators
2) Immediately replace the failed surge arrester
3) By July, 2023, ensure that all installed insulators in the POD area comply with the
creepage distance standard, 40 mm for 1 KV, line to line.
4) By July, 2023, survey the feeder and find the number of porcelain insulators exist in
the POD area, to be replaced with polymer insulators.
75
CHAPTER 5: CASE STUDY III - METERS’
CORRECTION FACTOR
5.1. Introduction
In 2020, an agreement between Aramco and SEC was reached, allowing Aramco to supply
energy to its offsite facilities through the national grid. Two types of meters were installed
based on this agreement, Main meters and Check meters. The Main meters are owned by
SEC and are used as the primary source of measurements, to be employed in calculating
the demand invoice. On the other side, Check meters are owned by Aramco and are used
as a secondary source for checking measurements.
Main meters are installed in SEC substations, while Check meters are installed in Aramco
facilities. A transmission line, ranging from 300 meters up to 13 Kilometers, connect
between the two meters. Due to this transmission line, some of the electric energy is
converted to thermal energy as it goes from main meter to check meter, meaning that, the
two meters do not read the same value. A slight difference shows up between the two
meters. That difference between the two meters is called Tie-line losses. Because of that, a
correction factor shall be established as shown below,
𝑀𝑎𝑖𝑛 𝑀𝑒𝑡𝑒𝑟 = 𝐶ℎ𝑒𝑐𝑘 𝑀𝑒𝑡𝑒𝑟 × 𝐶𝑜𝑟𝑟𝑒𝑐𝑡𝑖𝑜𝑛 𝐹𝑎𝑐𝑡𝑜𝑟 (5.1)
Whenever a power outage occurs to any of the Main meters, a correction factor will be
used to be approximate Main meter using Check meter. As agreed upon, it is Aramco’s
responsibility to establish the correction factor. Therefore, this case study will determine a
relation between the Main meter and Check Meter.
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Final Report.pdf

  • 1. King Fahd University of Petroleum and Minerals College of Engineering and Physics Electrical Engineering Department COOP Final Report Power System in Saudi Arabia Saudi Aramco Dhahran Hussain Al-Hussain 201846020 COOP Advisor: Dr. Motaz Alfarraj March 23, 2023
  • 2. I Abstract This report will present my training experience as a COOP student in Saudi Aramco, specifically at Power Operation Department as well as Power Planning Department. This report will delve into several subjects regarding power system in Saudi Arabia. Within it, the affiliate structure of the power system will be discussed. Also, this report will elaborate on various power generation topics, in which kingdom’s reliability on different technologies and fuels are going to be highlighted. A plan to expand the kingdom’s gas network will be outlined. In addition, A brief discussion on different transmission towers and poles will be introduced. More importantly, the Saudi Arabian Grid Code and Transmission Use of System agreement will be succinctly discussed. Furthermore, an inclusive revision of different electrical equipment, Uninterruptable Power Supplies and Power Transformers for instance, is presented. Three case studies are presented in this report. The first case study tests the validity to reuse a CO-9 Protective Relay. The second case study investigates the root causes of the power outage occurred in Power Operation Department, while the third one focuses on establishing a correction factor that will make two meters, installed in different locations, read the same energy demand.
  • 3. II Acknowledgement Thanks to Allah, for all the blessings that I, my family, and all the people have in this life. Thanks to my parents for their guidance and support continuously since I was born and though every milestone through my life. I am deeply thankful to everybody for helping me reach this milestone. My sincere gratitude goes to my supervisor in Aramco, Mohammed AL-Ghamdi, for his invaluable support, guidance and mentorship through my training period. I also want to express my appreciation to my colleagues at Aramco, Khalid Al-Rashidi, Rashed AL-Olayan, Muhana AL-Dakheel, Amer Alsubaie, and Murali, for their collaboration and support, which made every challenge surmountable. Turning to my academic pursuits, I am grateful to Dr. Motaz Alfarraj, my advisor at KFUPM, for his guidance and insights that enriched my academic experience. I extend my heartfelt thanks to all who contributed, both directly and indirectly, to my journey, as your contributions have left a lasting impact. This achievement is the result of the combined efforts and support of these remarkable individuals. Thank you all for being part of my success. King Fahd University of Petroleum and Minerals, Dhahran Electrical Engineering Department
  • 4. III Table of Content CHAPTER 1:INTRODUCTION ....................................................................................... 1 CHAPTER 2:TRAINING EXPERIENCE............................................................................. 5 2.1. MEMBERS OF POWER SYSTEM.................................................................................... 5 2.2. POWER GENERATION.............................................................................................. 12 2.3. POWER TRANSMISSION ........................................................................................... 25 2.4. POWER DISTRIBUTION............................................................................................. 40 CHAPTER 3:CASE STUDY I - ELECTROMAGNETIC RELAY TEST ..................................... 66 3.1. INTRODUCTION...................................................................................................... 66 3.2. METHODOLOGY..................................................................................................... 66 3.3. FINDINGS.............................................................................................................. 69 3.4. ANALYSIS.............................................................................................................. 70 3.5. CONCLUSION......................................................................................................... 70 CHAPTER 4:CASE STUDY II - POWER OUTAGE IN POD................................................ 71 4.1. INTRODUCTION...................................................................................................... 71 4.2. FIRST CASE ........................................................................................................... 71 4.3. SECOND CASE........................................................................................................ 71 4.4. ANALYSIS.............................................................................................................. 72 4.5. CONCLUSION......................................................................................................... 74 CHAPTER 5:CASE STUDY III - METERS’ CORRECTION FACTOR..................................... 75 5.1. INTRODUCTION...................................................................................................... 75 5.2. METHODOLOGY..................................................................................................... 76 5.3. FINDINGS.............................................................................................................. 78 5.4. ANALYSIS.............................................................................................................. 79 5.5. CONCLUSION......................................................................................................... 80 CONCLUSION............................................................................................................ 81 RECOMMENDATION................................................................................................. 82 REFERENCES............................................................................................................. 83 APPENDIX A: COOP PLAN ......................................................................................... 87 APPENDIX B: CALCULATING METERS’ CORRECTION FACTOR...................................... 89
  • 5. IV List of Figures Figure 1: Industry Structure of Saudi Energy Sector [3]............................................ 6 Figure 2: Operation of a Brayton Cycle Power Plant [7]......................................... 13 Figure 3: Operation of a Rankine Cycle Power Plant [10]....................................... 14 Figure 4: Operation of Combined Cycle Power Plant [12]...................................... 15 Figure 5: Current Fuel Mix in Saudi Arabia ............................................................ 18 Figure 6: Comparison Between Domestic and International Fuel Price [16]. ......... 19 Figure 7: Emission of Fuels Currently Used in Saudi Arabia [17]. ......................... 19 Figure 8: Saudi Arabian Oil Fields and Oil Facilities [19] ...................................... 26 Figure 9: Saudi Arabia’s Pipelines [18] ................................................................... 26 Figure 10: Saudi Arabia’s Shuaiba’s Pipeline............................................................ 27 Figure 11: An Illustration of Different Electrical Towers and Poles [20].................. 28 Figure 12: Transmission Tower Classification Based on Supply Circuits [21]. ........ 29 Figure 13: Components of a Transmission Tower ..................................................... 30 Figure 14: Procedure of Connecting to National Grid ............................................... 33 Figure 15: Connection of Off-Site Facilities.............................................................. 35 Figure 16: Equipment of Online Double Conversion UPS System [25].................... 42 Figure 17: Batteries of the UPS System..................................................................... 44 Figure 18: Representation of Transfer Switches ........................................................ 45 Figure 19: A Photograph of UPS Rectifier................................................................. 46 Figure 20: Illustration of a UPS Inverter.................................................................... 47 Figure 21: Left View of a Power Transformer........................................................... 51 Figure 22: Front View of a Power Transformer......................................................... 51 Figure 23: Power Transformer Components [28]. ..................................................... 52 Figure 24: Dehydrating Breather of Power Transformer [29].................................... 52 Figure 25: Connection of Insulation Resistance Test [30] ......................................... 54 Figure 26: Example of an SFRA Test Measurement [31].......................................... 55 Figure 27: An illustration of MCB, MCCB and RCCB, respectively........................ 57 Figure 28: A Photograph of a Breaker Panel [35]...................................................... 57 Figure 29: An Illustration of Coordination Characteristic. ........................................ 58 Figure 30: First Page of ANSI Standard Device Number [36]. ................................. 60 Figure 31: Second Page of ANSI Standard Device Number [36].............................. 61 Figure 32: Components of a CO-9 Electromagnetic Relay........................................ 65 Figure 33: CO-9 Magnetic Relay Characteristic Curve [37]...................................... 67 Figure 34: A Photograph of the Megger SVERKER 750 [38]................................... 68 Figure 35: Connection of SVERKER 750.................................................................. 68 Figure 36: Connection of CO-9 Relay........................................................................ 68 Figure 37: Pollution Flashover Progression of insulators [39]................................... 72 Figure 38: The Process of Contamination Discharge on Polluted Insulators [40]..... 73 Figure 39: Sorted Percentage Difference ................................................................... 77 Figure 40: Expected Correction Factor Trendline According to SEC. ...................... 78 Figure 41: Relation Between Distance and Correction Factor................................... 80
  • 6. V Figure 42: Main and Check Meters’ Readings Against Time.................................... 90 Figure 43: Difference Between Main meter and Check meter................................... 91 Figure 44: Demonstration of the Filter Function........................................................ 91 Figure 45: Lowest to Highest % Difference............................................................... 92 Figure 46: Procedure for Filtering Best 90% Readings.............................................. 93 Figure 47: Correction Factor Trendline and Slope..................................................... 94
  • 7. VI List of Tables Table 1: IPP and IWPP Groups [3]............................................................................... 7 Table 2: Renewable Energy Projects Overseen by MoE [4]......................................... 8 Table 3: Pros and Cons of Single Cycle Plants [8] [9]. .............................................. 14 Table 4: Scenario 1, No Change in Current Prices. .................................................... 20 Table 5: Scenario 2, HFO Price will be more expensive than gas going forward. ..... 20 Table 6: Conversion Factors. ...................................................................................... 21 Table 7: Summary of Given Parameters ..................................................................... 21 Table 8: Steps to Find Daily Fuel Consumption of HFO and Sales Gas. ................... 22 Table 9: Total Costs of Fuels in Scenario 1. ............................................................... 23 Table 10: Total Costs of Fuels in Scenario 2. ............................................................... 24 Table 11: Tariffs of Different End-users....................................................................... 37 Table 12: Given Parameters.......................................................................................... 37 Table 13: Cost of Purchased Energy per Load Type .................................................... 37 Table 14: TUoS Payment with Different Load Factors ................................................ 38 Table 15: Total Cost of Transferred Energy ................................................................. 38 Table 16: Cost Comparison (Purchased Energy – Transferred Energy)....................... 39 Table 17: Most Common ANSI Device Numbers ........................................................ 62 Table 18: Results of Time Dial Test ............................................................................. 69 Table 19: Results of Instantaneous Relay Coil Test ..................................................... 69 Table 20: Results of Current Tap Setting Test.............................................................. 69 Table 21: Summary of Facilities’ Correction Factors................................................... 79 Table 22: Assumed Meter’s Readings .......................................................................... 89 Table 23: Filtered Data with % Difference................................................................... 92 Table 24: Re-Filtered Meter’s Readings....................................................................... 94
  • 8. 1 CHAPTER 1: INTRODUCTION As you turn on the kitchen light switch, a circuit is closed connecting the breaker inside the house. The end connection of this breaker is at the transformer, installed outside the house. The cables that supply this transformer are hidden underground, and coming from a substation in which the voltage, specifically inside Saudi Arabia, is stepped down from 13.8 KV to 600 V for residential use. Inside this substation, protective equipment, like switchgear, relays, breakers, control panels and other equipment serves to prevent the occurrence of electric faults. At this substation, the cables are raised from underground to above a transmission tower. Multiple types of transmission towers carrying the cables exist. The general rule is, the more voltage contained in the cables, the higher and stronger the transmission towers are. This is to protect people from being shocked, since more voltage means greater distance that electrons can jump for. The cables, known as transmission lines, extend to pass through several substations, to finally reach the generators, found in the eastern and western side of the kingdom. The fuels, specifically crude oil and gas, extracted in the eastern side of the country, are primarily Aramco’s main industry. The company is introduced next. Saudi Aramco (the Arabian American Oil Company) is one of the largest integrated energy and chemicals companies in Saudi Arabia. Saudi Aramco creates value across the hydrocarbon chain, and deliver economic and societal benefits to the people and communities around the globe. Saudi Aramco aims to (1) reinforce its leading position in
  • 9. 2 oil and gas exploration and production, (2) enable the sustainable development of the Kingdom, and (3) lead the way in technology development and innovation [1]. Currently, Saudi Aramco is developing five mega projects which are: Fadhili Gas Plant, Manifa Bay, Sadara Chemical Company, Shaybah Power Plant and Wasit Gas Plant. Fadhili Gas Plant reflects Saudi Aramco’s dedication to reduce emissions, increase supplies of cleaner burning natural gas, and free up more crude oil for value-added refining and export. The Manifa shallow water oil field is one of the world's biggest producing oil fields. 328,500,000 barrels were produced in Manifa by 2017 [2]. The Sadara Chemical Company is a joint venture between both ARAMCO and the Dow Chemical Company. Sadara Chemical Company is constructing in Jubail Industrial City the world’s largest chemical complex ever built in a single phase. Shaybah Power Plant is a super-giant power plant under the control of Saudi Arabia which is located in the northern edge of the Rub' Al-Khali desert. Wasit Gas Plant is operating gas-fired power station in Al-Jubail, Eastern, Saudi Arabia, that supplies about 1400 MW. Speaking about my experience in Saudi Aramco, I was assigned with the Power System Planning department first in Saudi Aramco, to (1) have an introduction about the company’s goals, (2) have an overview to the power grid in Saudi Arabia, and (3) learn networking skills needed in the workplace. After that, to connect my theoretical knowledge with practical applications, I was sent temporarily to the Power Operation Department (POD). Until the 30th of March, I was rotating between units weekly to have an overview of distribution stage activities and operations. The Power Operation department hosts six units, each will be discussed briefly in the next page.
  • 10. 3 1) Maintenance Planning unit is responsible for creating plans for the other units, reviewing ongoing projects and dealing with contractors. 2) Uninterruptable Power Supply (UPS) & Renewables unit is responsible for maintaining the UPS System by undertaking weekly inspections and minor/major preventive maintenance. 3) Power Service unit is responsible for testing and maintaining the healthiness of heavy electrical equipment, including transformers, switchgears, gas switches, breakers, etc. 4) Electrical System Operation unit controls Aramco electrical network. It is responsible for isolating any electrical equipment before maintenance and investigation on the locations of electric faults. 5) Power Lines & Cables unit is responsible for mid/high voltage cables replacements, and inspection and maintenance on transmission towers. 6) Power Relay unit is responsible for troubleshooting and maintaining all of protective relaying and control systems within substations, power plants, large motors, etc. After completing my assignment in the Power Operation Department, I returned to the Power System Planning Department and joined three divisions, namely, National Regulations, Kingdom Utilities and Power Demand Analysis. The activities that these three departments are concerned with are discussed next. 7) National Regulation division is the point of connection between Aramco and the government. It is where codes, rules and regulations are reviewed to be considered in the company’s current and future projects.
  • 11. 4 8) Kingdom Utilities division deal with all parts of the kingdom, in regard to the planning of its utilities, for example, forecasting and planning fuel consumption, energy to be generated both renewable and non-renewable, and energy transmission and consumption locations. 9) Power Demand Analysis division is concerned with reviewing the data used to calculate peak demand, as well as deciding whether to transmit excess energy using TUoS (Discussed in subsection 2.3.4), or sell the excess energy as a spill. Through learning and working with the different units and divisions mentioned above, I gained knowledge in different spectrums, improving my skills and helping me realize the future of a typical power electrical engineer. This report summarizes important experience gained when working in Aramco, specifically in chapter 2, and presents three case studies in the remaining chapters, where chapter 3 and 4 were done in the Power Operation Department, while chapter 5 is completed in Power Planning Department.
  • 12. 5 CHAPTER 2: TRAINING EXPERIENCE This chapter summarizes my training experience in the COOP period. Section 2.1 discusses the structure of the power system, specifically the members who participate, regulate, or authorize the activities within the Power System. Section 2.2 explains different subjects about power generation in the kingdom. Section 2.3 explores the structure and material of transmission towers and poles. It then dives deep into regulations and policies that control the national grid. Section 2.4 summarizes characteristics of different necessary equipment used in electrical substations. 2.1. Members of Power System There are six players in the energy market, two of them are considered vital. The first and most important member in the energy market is the Ministry of Energy (MoE). MoE authorizes the opening of an energy field, for example, the opening of Solar energy market in the kingdom. MoE plans for the future, say, the next 10 years, before the authorization. Moreover, MoE is considered an important member of the power system, and therefore, a deeper view about MoE is provided in subsection 2.1.1. Second is Water & Electricity Regulatory Authority (WERA). WERA is the entity who regulates energy fields by establishing rules and policies to maintain the quality of energy services provided by companies. Also, WERA focuses on regulating the activities in the energy sector. Because of its importance, more details about WERA are provided subsection 2.1.2. Third, Principal Buyer (PB) is the sole buyer & seller of electricity. PB is sometimes referred to as Saudi Power Procurement Company. Fourth, National Grid, consisting of Transmission Service Provider (TSP) and Distribution Service Provider (DSP), is wholly
  • 13. 6 owned by Saudi Electricity Company (SEC). Fifth are the Generators, the ones responsible for generating energy, whether it is renewable or non-renewable, such as Aqua Power, Saudi Aramco Power Company, or SEC. Sixth are the Consumers, the ones who consume the energy. These can be industrial users such as machines in factories, can be citizens living in residential zones, can be employees working in commercial buildings such Clock Tower found in mecca, or can be for governmental services, schools and hospitals for instance. The current electricity industry structure is shown below in Figure 1. In the figure, IPP and IWPP are the groups of the companies illustrated in Table 1. Figure 1: Industry Structure of Saudi Energy Sector [3].
  • 14. 7 Table 1: IPP and IWPP Groups [3] Group Members Independent Power Producer (IPP) Hajr for Electricity Production Company Durmah Electric Company Rabigh Electric Company Al-Mourjan for Electricity Production Company Independent Water & Power Producer (IWPP) Jubail Water & Power Company Shuaibah Water & Power Company Shuqaiq Water & Power Company 2.1.1 Ministry of Energy Ministries have the highest responsibility within their sectors. They are the hand of the government that regulates all activity aspects of their dedicated sector. Accordingly, MoE monitors and regulates all activity aspects of energy sectors. MoE vision manifests itself in the aspiration of being an international leader in the field of energy and innovation. Furthermore, to achieve that vision, MoE established the mission; to be the leader in the energy sectors by first establishing development plans and programs that improve the added value of the sector, i.e., improve the service quality to raise the price of the sector services. And more importantly, by overcoming the economic challenges to maintain kingdom’s wealth, for instance, kingdom’s full dependence on fossil fuels. One of the solutions that MoE applied was to build renewable energy projects, shown on Table 2, where IPP PV stands for Independent Power Producer Photovoltaic.
  • 15. 8 Table 2: Renewable Energy Projects Overseen by MoE [4]. Project Type Location Production Capacity IPP PV Rahfa 20 MW IPP PV Medina 50 MW IPP PV Qurayyat 200 MW IPP PV Rabigh 300 MW IPP PV Jeddah 300 MW Wind Farm Dumat Al-Jandal 400 MW IPP PV Shuaibah 600 MW IPP PV Sudair 1500 MW IPP PV Sakaka 9500 MW MoE strives to accomplish its mission by achieving the following objectives: to (1) lead global energy markets, (2) optimize the production and consumption of hydrocarbons, which is a raw material used in lubricants, fuels, plastic, explosives, and other industrial chemicals, (3) be highly efficient in economic growth and consumption, and (4) maintain sustainability of the supplies by preserving the fortunes of the kingdom. In addition, for the reader to know which specific fields MoE works on, the most important units [5] that make up MoE are discussed next. 1) Optimum Allocation of Energy Resources Optimum Allocation of Energy Resources unit is responsible for receiving and reviewing orders related to allocating energy resources. One of the main jobs of this unit is to create
  • 16. 9 licenses for the pipelines of the energy distribution network. In fact, the unit also establishes the rules in coordination with energy source requester in order to get the license. More importantly, scrutinizing whether the established rules were compiled is within the unit responsibilities. 2) Policy and Strategic Planning Policy and Strategic Planning is responsible for collecting and revising data to develop strategic plans and complete policies for the energy sector. 3) Development of Local Content, Crisis Management, and Risk This unit is responsible for increasing domestic production in the energy sector by working with all energy concerned parties. Also, the unit is responsible for creating jobs to reduce unemployment in the kingdom. Last, searching for possible risks in the national grid is part of unit’s obligations. 4) Electricity Affairs Duties of Electricity Affairs unit are demonstrated in: (1) developing energy services that increases the added value of energy sector, (2) reinforcing the electrical grid to have enough capacity, that is, to receive different kinds of energy, especially the promised renewable energy projects. Finally, (3) inspect whether users of the national grid complied with rules mentioned in the Distribution Code.
  • 17. 10 5) Renewable Energy Renewable Energy unit is solely obligated to develop strategic plans that advance renewable energy projects. Part of their work is to study the global energy market and gain insight from other countries, to apply the learnt information in supporting domestic projects. 6) Regulation of Petroleum and Gas The responsibility of Regulation of Petroleum and Gas unit is to supervise and regulate all activity aspects associated with the three sectors, namely. Petrol sector, gas sector, and petrochemical sectors. 7) International Relations and Cooperation Creating and reinforcing a strong relationship between Saudi Arabia and other countries, both gulf and non-gulf, in pertaining to energy sectors is the unit’s main objective. The unit also studies and analyzes the international shared objectives, which helps in identifying areas of cooperation, and avoiding any potential conflicts between the kingdom and neighboring countries. 8) Sustainability and Climate Change The duties of this unit are many. Therefore, the most general duties are only mentioned. The first duty is giving the needed support against climate change, specifically, the yearly increase of temperature due to global warming. The second duty is to participate in putting strategies to increase clean energy as illustrated in Table 2. The third duty is to develop the
  • 18. 11 environmental policies related to the energy sector, while the last one is to monitor the implementation of the carbon circular economy and promote it. In fact, Carbon circular economy manifests in creating something that is known to be dismantled and restored later, because even though the kingdom’s resources are abundant, they can be easily depleted if not used wisely. These are the vital units that make up MoE. WERA is discussed next. 2.1.2 Water & Electricity Regulatory Authority WERA regulates the electricity and water desalination sector within the Kingdom. WERA’s vision is to make water and electricity reach a sustainable state, and at the same time, guarantee to give the best services that comply with the global standards in terms of quality, efficiency and inclusivity [6]. WERA will achieve its vision by guaranteeing to the consumers that electrical service providers deliver services of high quality, complete, dependable and at a reasonable price. Next, the objectives of the WERA are to: 1) Create a suitable environment that encourages competition between water and electricity service providers. 2) Encourage investors to share in improving power generation and water desalination sectors, and enable them to make economic profits. The reasons to do so is demonstrated in this case. Whenever investors invest in the kingdom, they will open an outlet of their company, business, or enterprise in Saudi Arabia. Because of that, the branch opened in Saudi Arabia must comply with all the rules and policies, for example, nationalization of the workforce, which will decrease the rate of unemployment. In addition to that, the 15% tax payment must be submitted for any
  • 19. 12 service or product presented by the branch to the kingdom, increasing kingdom’s wealth. 3) Protect Public interest and consumers’ rights by providing high quality water and electricity services with reasonable prices. 2.2. Power Generation This section briefly explains the diverse generation technologies employed in Saudi Arabia. Following this, the extent to which the kingdom relies on the mentioned technologies is outlined. After that, this section explains the kingdom’s dependence on various fuels used to generate power. Finally, this section concludes with an exercise that demonstrates how to calculate the consumption of fuels in a power plant. 2.2.1 Generation Technologies Three technologies are applied when generating electricity, these are: Simple Cycle, Combined Cycle and Co-generation. The process of each technology with its operational times is discussed briefly Next. First is the Simple Cycle. Because of its fast start up, Simple Cycle technology is used whenever power demand is high, especially at noon, when numerous air conditioners are operating. The process of Simple cycle technology is as follows: A simple cycle power plant (1) pumps the received air, (2) mixes it with natural gas and burns it to produce a high-pressure (HP) gas, (3) uses this gas to move the turbine which results in moving generator’s rotor; thus, produce electric energy. This is called Brayton Cycle, depicted in Figure 2.
  • 20. 13 Figure 2: Operation of a Brayton Cycle Power Plant [7]. Another method to do the same job in which water is used in place of air is called the Rankine cycle, illustrated in Figure 3. The process of a Rankine cycle power plant is explained next. First, water goes into a pump, to increase the water pressure. Second, the HP water goes into a boiler to be vaporized and converted into steam. Third, this steam is used to move the turbine, and the turbine will move the rotor of a generator, thus generating electricity. Fourth, outlet steam is cooled and condensed to be reused in generating the steam, starting the loop from the beginning. Additionally, the advantages and disadvantages of a Simple Cycle power plant are briefly mentioned on Table 3.
  • 21. 14 Table 3: Pros and Cons of Single Cycle Plants [8] [9]. PROS CONS Fast Start-up, in as low as minutes Low Heat Efficiency (33.8%) Cheap Construction Expensive Operation & Maintenance Space-saving Much Emission is Produced Figure 3: Operation of a Rankine Cycle Power Plant [10]. Second is the Combined Cycle. Combined Cycle technology is the combination of both Brayton Cycle and Rankine Cycle. In Combine Cycle, the same fuel is used in both cycles. The difference between Single Cycle and Combined Cycle is in the use of exhausted air. To explain, whereas Single cycle generators exhaust all the low-pressure gas, Combined cycle generators utilize it to produce more power. Utilizing the exhausted gas resulted in almost doubling the efficiency of the generators, from 33.8% (Single cycle generators) to
  • 22. 15 at least 60% (Combined Cycle generators), and on top of that, the CO2 emission is reduced by 50% [11]. The operation of Combined cycle technology is demonstrated in Figure 4. The blue side represents the Brayton Cycle, while the green side is where the exhausted air from Brayton Cycle is exploited (Rankine Cycle). The complete process of a combined cycle power plant is explained next. First, the exhausted air enters the heat recovery steam generator, which vaporizes the water using the heat of the exhausted gas. Then, HP steam is used to move the turbine in order to generate electricity. After using the HP steam by the generator, a low-pressure (LW) steam resulted, and is injected to the air condenser to convert steam back into water, and water is pumped to be reused by the heat recovery steam generator. Figure 4: Operation of Combined Cycle Power Plant [12].
  • 23. 16 Last Power technology is Co-generation. Co-generation is indeed a part of Combined Cycle technology. Co-generation is the production of both electricity and Steam. In Combined Cycle technology, steam is used only to generate more electricity. However, in Cogeneration, steam is sold as is, since it can be used in a much wider scope. One application is to use the heat of the steam to separate chemical compounds of the gas that is used in Brayton Cycle, e.g., separate methane and ethane from the gas to sell each one individually. Another application is to use steam as a source that moves pumps. This is done by moving the steam through a turbine that rotates a pump, to increase the pressure of other gases or liquids. A third application is to heat other fluids using steam. For the power sector, companies such as SEC prefer combined cycle technology over Combined Cycle technology. However, in the context of oil and gas companies like Aramco, co- generation technology proves to be a more advantageous and practical option. To summarize, whenever electricity is needed for demand peaking time, Simple cycle plants are used. If electricity is needed continuously, Combined Cycle plants are used. If, however, steam is needed for any such applications, Co-generation plants are used. 2.2.2 Generation Mix By generation mix, the author means the amount of reliance on different technologies used in Saudi Arabia. The main three technologies used in electricity generation inside Saudi Arabia are: Gas Turbine (Brayton Cycle), Steam Turbine (Rankine Cycle), and Combined Cycle. The total energy generation of kingdom of Saudi Arabia, as per 2017 data, is 289 TWh, with power capacity of 90 GW distributed between the three technologies as 49.8% for Steam Turbines, 35.4% for Gas Turbines, 13.9% for Combined Cycle units [3].
  • 24. 17 The average capacity of one unit of Steam Turbine (ST), Gas Turbines (GT), and Combined Cycle (CC), is 37 MW [13], 29.98 MW [14], and 820 MW [15] respectively. In other words, an estimation of 1200 units of STs, 1050 units of GTs and 15 units of CC exist in the kingdom. As will be shown later, gas turbines exist on the eastern side of the country, because of the much availability of gas there, and steam turbines exist on western side of the country, because of the easy access to water at that location. The eastern and western sides of the country supply energy to the whole country. According to KSA 2030 Vision, our generation mix will shift to depend solely on the two technologies, namely, GTs and Renewable Energy technology. To be exact, the capacity of the country must be 50% for Renewables, and 50% for GTs. The reader is suggested to refer to Table 2 to check the current progress of KSA towards having 50% renewable energy in the country. 2.2.3 Fuel mix in the kingdom As per Aramco’s 2017 data, the current fuel mix for the kingdom, as depicted in Figure 5, is distributed between four types of fuels. These are Natural Gas, Crude Oil, Heavy Fuel Oil (HFO) and finally Diesel. Most of the power generated is by combusting Natural Gas, making up 44% of power generation capacity. On the other hand, Diesel, the least burned fuel, makes up only 7% of the generation capacity. Reasons for that are further explained afterwards. In the middle are HFO and Crude Oil, making up 28% and 21% of the capacity, respectively.
  • 25. 18 Figure 5: Current Fuel Mix in Saudi Arabia As mentioned before in 2.2, one objective of vision 2030 is to stop using liquid fuels completely, and shift the dependance on gas and renewable energy. This is to decrease energy costs, by removing the subsidies given to liquid fuel sellers; and to protect the environment, by reducing carbon emissions produced from fuel combustion. To illustrate, Figure 6 shows the significant reduction in domestic diesel price, which can be recovered by removing Saudi governmental subsidies, and Figure 7 in turn demonstrates a significant difference in the emissions of gas compared to the other liquid fuels. One third of the emissions coming out from combusting HFO can be eliminated if gas is used instead. 44% 28% 21% 7% CONSUMPTION OF DIFFERENT FUELS IN SAUDI ARABIA Natural Gas HFO Crude Oil Diesel 90 GW
  • 26. 19 Figure 6: Comparison Between Domestic and International Fuel Price [16]. Figure 7: Emission of Fuels Currently Used in Saudi Arabia [17]. 23.14 71.73 119.85 116.84 0.00 20.00 40.00 60.00 80.00 100.00 120.00 140.00 Diesel GAS Price of Fuel (SAR/MMBtu) Diesel Price Comparison Domestic International 0.27 0.18 0.25 0 0.05 0.1 0.15 0.2 0.25 0.3 HFO GAS Diesel Emission Factor (Kg/KWh) Emission of Different Fuels
  • 27. 20 2.2.4 Fuel Consumption Exercise The problem statement is as follows. Consider Rabigh Power Plant facility with the following parameters: • The plant has 4 units running on HFO. • The first two units are 300 MW while the other two units are 800 MW • Efficiencies at 25% and 35%, respectively. • Plant utilization rate is 90%, with annual interest rate of 6% Assuming steady demand and steady generation throughout the year, calculate: 1) The plant’s daily fuel consumption using HFO. 2) The plant equivalent consumption using sales gas. 3) If the total cost (Capex) to convert the plant to burn sales gas instead of HFO is $41,000. Calculate the Net Present Value from the fuel savings from 2022 till 2030 considering the following fuel cost profiles: Table 4: Scenario 1, No Change in Current Prices. Year 2022 2023 2024 2025 2026 2027 2028 2029 2030 HFO ($/MMBTU) 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 Sales Gas ($/MMBTU) 1.25 1.25 1.25 1.25 1.25 1.25 1.25 1.25 1.25 Table 5: Scenario 2, HFO Price will be more expensive than gas going forward. Year 2022 2023 2024 2025 2026 2027 2028 2029 2030 HFO ($/MMBTU) 0.6 0.9 1.2 2.1 4.0 5.6 7.4 8.9 9.8 Sales Gas ($/MMBTU) 1.25 1.25 1.25 1.25 1.25 1.25 1.25 1.25 1.25
  • 28. 21 Table 6: Conversion Factors. Electric to Thermal Conversion Factor (MMBtu/MWh) Thermal Energy Per Barrel (MMBtu/BBL) Number of Hours per year Thermal Energy Per Standard Cubic Foot (MMBtu/SCF) 3.412 6.327 8760 1080 Table 7: Summary of Given Parameters Unit Parameter A B C D Capacity (MW) 300 300 800 800 Efficiency 25.00% 25.00% 35.00% 35.00% Utilization Rate 90.00% 90.00% 90.00% 90.00% Power Plant Conversion Capex $41,000 Annual Interest Rate 6.00% The solution to this problem can be approached by summarizing the information given in the problem above in Table 7. First, to find the daily fuel consumption of HFO, required in the first part of the problem, the unit of the capacity (MW) needs to be converted to the unit of heat (MMBtu), and after that, by dividing by Thermal Energy Per Barrel, heat is converted to Barrels of HFO (BBL). A step-by-step solution is provided next. The reader is suggested to refer to Table 8 shown in the next page as he reads the following steps. To calculate how much of the capacity has been utilized, the capacity of the power plant is multiplied by the utilization rate (Step 1) to find the utilized energy. After that, to convert the utilized energy into heat, while taking the efficiency into account, the utilized energy
  • 29. 22 is divided by the efficiency and, at the same time, multiplied by Electric to Thermal Conversion Factor (Step 2), thus, resulting in the hourly heat utilized by the unit. First, to find the number of barrels used for each unit, simply divide the hourly heat utilized by the conversion factor Thermal Energy Per Barrel, and multiply the answer by 24 to convert the hours to days (Step 3), since daily fuel consumption is required. Second, to find the daily consumption of sales gas, as needed in part 2 of the problem, steps 1 and 2 must be repeated to find the hourly heat utilized. Next, the hourly heat utilized is divided by the conversion factor Thermal Energy per Standard Cubic Foot, and again, since sales gas is required daily, the answer is also multiplied by 24 (Step 4). The answers to parts 1 and 2 of the problem are shown in Table 8. Third, to calculate the NPV of both scenarios, we need to find the total yearly heat utilized. This is done by multiplying the total hourly heat utilized found in step 2 by 8760, which is the number of hours in a year. After that, multiply the price of HFO by the total yearly heat utilized to find the yearly cost of producing HFO. Table 8: Steps to Find Daily Fuel Consumption of HFO and Sales Gas. Steps Parameter A B C D Total Step 1 Energy Capacity (MWh) 300 300 800 800 2,200 Utilized Energy (MWh) 270 270 720 720 1,980 Step 2 Hourly Heat Utilized (MMBtu) 3,685 3,685 7,019 7,019 21,408 Step 3 Daily Barrels Needed (BBL) 13,978 13,978 26,625 26,625 81,206 Step 4 Daily Gas Needed (SCF) 82 82 156 156 476
  • 30. 23 Applying this reveals that the total cost of HFO, as based on scenario 1, is $112,519,727 dollars yearly, meaning that it does not change. Doing the same, that is multiplying the total yearly heat required by the price of Sales gas, gives the yearly cost of producing Sales Gas. More importantly, if we were to convert the Rabigh Power Plant from HFO to Sales gas, the first year will have only Capex cost, which is $41,000. The following years will be the difference between HFO costs to Sales Gas costs, as will be shown later. For Scenario 1, with unchanged HFO prices. The NPV is -$714,143,708. This means that Rabigh Power Plant, if converted to Sales Gas, will cause a loss of more than 700 million dollars. Table 9: Total Costs of Fuels in Scenario 1. Scenario 1 Year Total Cost (HFO) Total Cost (Gas) Differential (Gain) NPV 2022 $112,519,727 $234,416,098 -$41,000 -$714,143,708 2023 $112,519,727 $234,416,098 -$121,896,371 2024 $112,519,727 $234,416,098 -$121,896,371 2025 $112,519,727 $234,416,098 -$121,896,371 2026 $112,519,727 $234,416,098 -$121,896,371 2027 $112,519,727 $234,416,098 -$121,896,371 2028 $112,519,727 $234,416,098 -$121,896,371 2029 $112,519,727 $234,416,098 -$121,896,371 2030 $112,519,727 $234,416,098 -$121,896,371
  • 31. 24 However, as mentioned earlier in section 3 (Fuel mix in the kingdom), the government plans to remove the subsidies from all liquid fuels, which for sure causes the price of HFO to increase significantly. Scenario 2 anticipates the change of increasing the price of HFO. Repeating the calculation done before with the expected HFO prices results in NPV to be $3,636,575,644, that is, the profits of this project, if the price of HFO changed as expected, will exceed three and a half billion dollars. This project will break even between the years 2024 to 2025, as shown in the table below. Table 10: Total Costs of Fuels in Scenario 2. Scenario 2 Year Total Cost (HFO) Total Cost (Gas) Differential (Gain) NPV 2022 $112,519,727 $234,416,098 -$41,000 $3,636,575,644 2023 $168,779,591 $234,416,098 -$65,636,508 2024 $225,039,454 $234,416,098 -$9,376,644 2025 $393,819,045 $234,416,098 $159,402,947 2026 $750,131,515 $234,416,098 $515,715,416 2027 $1,050,184,120 $234,416,098 $815,768,022 2028 $1,387,743,302 $234,416,098 $1,153,327,204 2029 $1,669,042,620 $234,416,098 $1,434,626,522 2030 $1,837,822,211 $234,416,098 $1,603,406,112 It is important to note for the reader that this is a real project that is going to be done by Aramco. The prices used here may not be as accurate as in their calculations, because real
  • 32. 25 data is considered government confidential, meaning that the author does not have access to these data. However, real data are not far away from the numbers above based on what Nassar, the supervisor of Kingdom Utilities division in Aramco, said. 2.3. Power Transmission This section shows first the kingdom's gas network with the plan to expand it. It then covers briefly classifications and types of transmission towers and poles. After that, it outlines Saudi Arabian Grid Code, and dives deep to the operations and an agreement regarding the grid. Finally, an exercise is solved to explain the usefulness of Transmission Use of System agreement. 2.3.1 Current and Future Gas Network Currently, the kingdom of Saudi Arabia depends on two types of fuels: Gas and Crude Oil. These fuels are extracted from Earth in Oil fields. After extraction, fuels are sent to Oil Facilities for the purpose of separating and removing impurities from fuels. Figure 8 in the next page shows the different oil fields and oil facilities of the kingdom, in blue and green, respectively. The facilities and fields of oil are all connected to Abqaiq facility, and from there, fuels are transported via pipelines across Riyadh to finally reach Yanbu, as shown in Figure 9 where they are represented as orange lines. At Yanbu, a 3100 MW power plant utilizes transported fuel. Indeed, there are two pipelines, one pipeline with 56-inch in diameter to transport oil, and the other is a 48-inch diameter to transport natural gas [18]. The kingdom plans to expand and install new pipelines running from Riyadh to Shuaiba. The purpose of doing so is to utilize the largest power plant in Saudi Arabia, the Shuaiba
  • 33. 26 Power and Desalination Plant located in the south of Jeddah, with a total capacity of 5.6 GW [18]. The new pipeline is shown below in Figure 10. Figure 8: Saudi Arabian Oil Fields and Oil Facilities [19] Figure 9: Saudi Arabia’s Pipelines [18] Riyadh Yanbu
  • 34. 27 Figure 10: Saudi Arabia’s Shuaiba’s Pipeline. 2.3.2 Transmission Towers & Poles After generating electricity in power plants, and after stepping up its voltage, overhead transmission lines carry the electricity to industrial, commercial, or residential loads. Along the way, Transmission Towers and the poles carry heavy conductors. These two are categorized based on their voltage level, construction material, and finally number of lines carried. Based on Voltage, they can be classified as High Voltage, for more than 69 KV, medium voltage, between 600 V to 69 KV, and low voltage, under 600V. Speaking about the construction material, the standard material used in building transmission towers is steel, due to its strength, lightweight, and most importantly, its inexpensive cost. If more durability is needed, for example, in areas that experience seismic activities, then concrete is used instead in building them. More durability comes with an increased costs because of concrete price. While concrete poles and steel transmission towers are used to carry Riyadh Yanbu Shuaiba
  • 35. 28 medium and high voltage lines, respectively, wooden transmission poles are used in low voltage lines. This is mainly because of their low cost, ignoring their lack of strength and durability. The mentioned types are shown in Figure 11. Finally, when it comes to the number of lines carried, Transmission Towers can carry cables that feed single circuits, double circuit, or multiple circuits. Single circuit transmission towers carry low voltage transmission lines, double circuit carry medium voltage, and multiple circuit carry high voltage conductors. The three types are shown in Figure 12. Figure 11: An Illustration of Different Electrical Towers and Poles [20].
  • 36. 29 Figure 12: Transmission Tower Classification Based on Supply Circuits [21]. A typical transmission tower consists of the following components: 1) Cross Arms: used to carry power lines. 2) Insulator: used to hold power lines in place, and keep them isolated from transmission tower. Since transmission towers are conductive, any power line touching the transmission tower will cause electricity to flow to earth, resulting in a ground fault. 3) Cable Raiser: used to raise the cables and keep them insulated from the tower. 4) Buss Bar: used to combine the energy from two cables into a single line. 5) Lightning Arrester: used to protect the transmission line and tower from lightning, creating a path for excess electricity to flow directly to ground. 6) Skirts: Used to insulate the tower from the power cables. This is to increase the protection on the cables from lighting. By increasing the resistance of the cable insulation, the current coming from the lightning will be guided towards earth directly.
  • 37. 30 7) Guy Strain Insulator: This is to insulate the guy wire (a wire that is used to support in holding transmission tower from leaning) from the transmission tower. All the components are depicted in Figure 13. Figure 13: Components of a Transmission Tower
  • 38. 31 2.3.3 Saudi Arabian Grid Code To ensure a safe, reliable, and efficient operation of the grid, WERA created the SAGC (Saudi Arabian Grid Code). SAGC is a technical regulatory document that defines the obligations and responsibilities to the owner of the grid, that is SEC, and to all Users of the grid. SAGC is written specifically for the generation and transmission parts of the power system, while the Saudi Arabian Distribution Code, a document similar to SAGC, is dedicated to the distribution stage. Within the SAGC, six major codes are discussed, which are Connection Code, Planning Code, Operating Code, Metering Code, Data & Information Exchange Code, and finally Scheduling and Dispatch Code. All the above codes set the minimum requirement and rules that must be followed in order to comply with SAGC. Before introducing the codes, it is better to start with the general conditions, which connect and clarify any potential misconception with the above codes. General Conditions contains provisions that are applied to all sections of the Grid Code. Their main objective is to ensure that different sections of the Grid Code work collectively and in harmony. General problems that Users may face are discussed in this section, for example, when should a condition of the grid code be skipped, how to settle a dispute, and etcetera. Connection Code focuses on any connection related topics, connection agreements, transmission system performance like frequency or voltage variations, operation, and maintenance safety conditions…etc. The reader is suggested to refer to this section whenever his needs are technical and related to the connections between the grid and Users. Note that all plants and apparatus at the Connection Point shall comply with the relevant
  • 39. 32 TSP (Transmission Service Provider) standards, or in their absence, other IEC, ANSI, or IEEE standards. The procedure to connect to the national grid is demonstrated in Figure 14. Planning Code is intended for tasks that are related to the development and expansion of the transmission system. It also specifies the data that should be exchanged between the TSP and Users of grid. Planning, responsibilities, processes, and the grid information is covered in detail in this section. Operating code covers the topics that are related to proper operation of the Grid, for example, energy demand forecasting, maintenance planning for electricity generation and transmission, management of system support services, contacting between the TSP and Users and coordination of Safety. Apart from this, to avoid blackouts, black start stations are used, which are generators that start up whenever a power outage occurs to a city. Methods of investigation and verification of performance are explained in this section. Scheduling and Dispatch Code specifies the responsibilities and obligations of the TSP and Users regarding scheduling and dispatching of generating units and demand resources. Moreover, this code establishes a procedure for users to supply accurate information to TSP. After that, the TSP prepares and issues Generation Schedules and Dispatch Instructions. Metering Code sets out the regulations and rules for metering and recording requirements for Participants. In addition, it clarifies the obligations of the participants related to such installations of meters. Furthermore, it also establishes important technical design and operational criteria that grid participants shall comply with in terms of metering and data collection of equipment and installations.
  • 40. 33 Figure 14: Procedure of Connecting to National Grid
  • 41. 34 2.3.4 Features of National Grid. Large Companies, especially ones that produce electricity like Aramco, have a complex relationship with SEC where they can use grid infrastructure for various operational purposes. Their relation can be understood through three main ways: Spill mechanism, wheeling strategy and security of supply. Each of these ways is explained below. Spill Mechanism: When a company produces more energy than it needs, the company sells the extra energy to PB. This excess energy is distributed to other users of the grid. The price of this energy is typically much lower than the one purchased from PB, due to the fact that PB is the only customer in the energy market who can purchase this energy, as explained in section 2.1. Although the price of the sold excess energy is low, it is considered a very good way to reduce surplus energy losses. Wheeling Strategy: in this strategy, companies are allowed to transfer their excess energy through the grid, enabling an efficient energy distribution across different parts of companies’ outlets. Due to the fact that all cities of the kingdom are connected to the power grid, the company will not face difficulties in transferring its excess energy even if its energy generators are far away from its outlet, say, one in the eastern side of the kingdom while the other is at the center. Companies can transfer their excess energy after signing the Transmission Use of System agreement, explained in detail in the next section. Security of Supply: This strategy serves to protect companies from power outages. To explain, when companies’ energy resources are depleted, companies can directly utilize the power supplied by the grid, preventing the stoppage of their operation. Demand meters are employed to measure the amount of power that has been consumed from the grid, which is used later in calculating electricity consumption invoice to be paid for PB.
  • 42. 35 2.3.5 TUoS Agreement Transmission Use of System (TUoS) is an agreement that governs wheeling, that is the transmission of excess power, from one facility to the other. To explain, worldwide oil and gas companies, like Aramco, usually build power plants to generate their needed electricity, since it is cheaper for them in the long run. However, some outlets of the company are not directly connected to their generators, it is connected to company’s generators through the grid, which are called off-site facilities, as shown in Figure 15. Figure 15: Connection of Off-Site Facilities Therefore, to feed energy to the off-site facilities, the company is bound between two choices. First choice is to agree upon the TUoS agreement and pay its related taxes. The second choice is to purchase electricity directly from PB. Assuming that the company agrees upon TUoS Agreement, then it must pay the TUoS Payment and Bulk Supply Charge (BSC), defined in (2.1) and (2.2). Otherwise, if the company would like to buy electricity directly from PB, then it must pay PB invoice, given in (2.3). Note that the average of demand peaks, shown in all three equations, is calculated using (2.4). In addition, the load factor, as described in (2.5), is analogous to the efficiency of paid
  • 43. 36 electricity. For example, when a company pays an invoice with low load factor, say 10% load factor, it means 100 MW was purchased, but only 10 MW is received. 𝑇𝑈𝑜𝑆 𝑃𝑎𝑦𝑚𝑒𝑛𝑡 (𝑆𝐴𝑅) = 𝑇𝑈𝑜𝑠 𝑃𝑟𝑖𝑐𝑒 ( 𝑆𝐴𝑅 𝐾𝑊 ) × 𝐴𝑣𝑒𝑟𝑎𝑔𝑒 𝑜𝑓 3 𝑑𝑒𝑚𝑎𝑛𝑑 𝑝𝑒𝑎𝑘𝑠(𝐾𝑊) 𝐿𝑜𝑎𝑑 𝑓𝑎𝑐𝑡𝑜𝑟 (2.1) 𝐵𝑆𝐶(ℎℎ) = 𝐵𝑆𝐶 𝑡𝑎𝑟𝑟𝑖𝑓 ( ℎℎ 𝐾𝑊ℎ ) × 𝑌𝑒𝑎𝑟𝑙𝑦 ℎ𝑜𝑢𝑟𝑠(ℎ) × 𝐴𝑣𝑒𝑟𝑎𝑔𝑒 𝑜𝑓 3 𝑑𝑒𝑚𝑎𝑛𝑑 𝑝𝑒𝑎𝑘𝑠(𝐾𝑊) (2.2) 𝑃𝐵 𝐼𝑛𝑣𝑜𝑖𝑐𝑒(𝑆𝐴𝑅) = 𝑇𝑎𝑟𝑟𝑖𝑓 ( 𝑆𝐴𝑅 𝐾𝑊ℎ ) × 𝑌𝑒𝑎𝑟𝑙𝑦 𝐻𝑜𝑢𝑟𝑠(ℎ) × 𝐴𝑣𝑒𝑟𝑎𝑔𝑒 𝑜𝑓 3 𝑑𝑒𝑚𝑎𝑛𝑑 𝑝𝑒𝑎𝑘𝑠 (𝐾𝑊) (2.3) 𝐴𝑣𝑒𝑟𝑎𝑔𝑒 𝑜𝑓 3 𝑑𝑒𝑚𝑎𝑛𝑑 𝑝𝑒𝑎𝑘𝑠 = 𝑃𝑒𝑎𝑘 1 + 𝑃𝑒𝑎𝑘 2 + 𝑃𝑒𝑎𝑘 3 3 × 𝑇𝑈𝑜𝑆 𝑃𝑟𝑖𝑐𝑒 (2.4) % 𝐿𝑜𝑎𝑑 𝑓𝑎𝑐𝑡𝑜𝑟 = 𝐴𝑣𝑒𝑟𝑎𝑔𝑒 𝐿𝑜𝑎𝑑 𝑀𝑎𝑥𝑖𝑚𝑢𝑚 𝐿𝑜𝑎𝑑 × 100 (2.5) 2.3.6 TUoS Exercise The problem Statement is: should a company purchase electricity directly from SEC, or transfer the excess power from its generators? Given that the average power consumption of the company is 100,000 KW, Current TUoS Price is 287.4 Sar/KW, and tariffs are as given in SEC website. The tables in the next page summarize the information needed to solve the problem. The tariffs, as given by SEC, with other parameters are shown in Tables 11 and 12, respectively. The cost of purchasing power directly from SEC for all types of loads is found using (2.3). Results are shown on Table 13.
  • 44. 37 Table 11: Tariffs of Different End-users Table 12: Given Parameters Table 13: Cost of Purchased Energy per Load Type Now, to find the price for wheeling the excess power, the Bulk Supply Charge must be calculated first using (2.2). 𝐵𝑆𝐶(𝑆𝐴𝑅) = (8.3)/100 ∗ (24 ∗ 365) ∗ (100000) End-User Tariffs (hh/KWh) Residential 30 Commercial 30 Agricultural 20 Governmental 32 Industrial 18 Private Education Facilities 18 Avg of Demand Peaks 100000 KW TUoS Price 287.4 SAR/KW Bulk Supply Tariff 8.3 hh/KWh Yearly Hours 8760 h End-User Energy Cost Purchased (SAR) Residential $262,800,000 Commercial $262,800,000 Agricultural $175,200,000 Governmental $280,320,000 Industrial $157,680,000 Private Education Facilities $157,680,000 Table 11: Tariffs of Different End-users Table 12: Given Parameters Avg of Demand Peaks 100000 KW TUoS Price 287.4 SAR/KW Bulk Supply Tariff 8.3 hh/KWh Yearly Hours 8760 h Table 12: Given Parameters
  • 45. 38 Resulting in 𝐵𝑆𝐶 = 72,708,000 𝑆𝑎𝑟 Next to find the TUoS Payment, (2.1) is used. Different arbitrary load factors are assumed. Therefore, we have the following results shown in Table 14. Adding Table 14 to the Bulk Supply Charge gives the total costs for transferring energy, shown in Table 15. Finally, a comparison between the costs of purchasing electricity from SEC and transferring excess energy is shown in the next page, Table 16, where simply the green number stands for revenues, and, conversely, red number is for losses. Table 14: TUoS Payment with Different Load Factors Table 15: Total Cost of Transferred Energy Load Factor TUoS Payment (SAR) Bulk Supply Charge Load Factor TUoS Total Cost (SAR) 100.00% $28,740,000 $72,708,000 100.00% $101,448,000 95.00% $30,252,632 95.00% $102,960,632 90.00% $31,933,333 90.00% $104,641,333 85.00% $33,811,765 85.00% $106,519,765 80.00% $35,925,000 80.00% $108,633,000 75.00% $38,320,000 75.00% $111,028,000 70.00% $41,057,143 70.00% $113,765,143 65.00% $44,215,385 65.00% $116,923,385 60.00% $47,900,000 60.00% $120,608,000 55.00% $52,254,545 55.00% $124,962,545 50.00% $57,480,000 50.00% $130,188,000 45.00% $63,866,667 45.00% $136,574,667 40.00% $71,850,000 40.00% $144,558,000 35.00% $82,114,286 35.00% $154,822,286 30.00% $95,800,000 30.00% $168,508,000 25.00% $114,960,000 25.00% $187,668,000 20.00% $143,700,000 20.00% $216,408,000 15.00% $191,600,000 15.00% $264,308,000 10.00% $287,400,000 10.00% $360,108,000 5.00% $574,800,000 5.00% $647,508,000 Table 14: TUoS Payment with Different Load Factors Table 14: TUoS Payment with Different Load Factors Table 15: Total Cost of Transferred Energy Table 15: Total Cost of Transferred Energy
  • 46. 39 Table 16: Cost Comparison (Purchased Energy – Transferred Energy). Load Factor Residential Commercial Agricultural Governmental Industrial Private Education Facilities 100.00% $161,352,000 $161,352,000 $73,752,000 $178,872,000 $56,232,000 $56,232,000 95.00% $159,839,368 $159,839,368 $72,239,368 $177,359,368 $54,719,368 $54,719,368 90.00% $158,158,667 $158,158,667 $70,558,667 $175,678,667 $53,038,667 $53,038,667 85.00% $156,280,235 $156,280,235 $68,680,235 $173,800,235 $51,160,235 $51,160,235 80.00% $154,167,000 $154,167,000 $66,567,000 $171,687,000 $49,047,000 $49,047,000 75.00% $151,772,000 $151,772,000 $64,172,000 $169,292,000 $46,652,000 $46,652,000 70.00% $149,034,857 $149,034,857 $61,434,857 $166,554,857 $43,914,857 $43,914,857 65.00% $145,876,615 $145,876,615 $58,276,615 $163,396,615 $40,756,615 $40,756,615 60.00% $142,192,000 $142,192,000 $54,592,000 $159,712,000 $37,072,000 $37,072,000 55.00% $137,837,455 $137,837,455 $50,237,455 $155,357,455 $32,717,455 $32,717,455 50.00% $132,612,000 $132,612,000 $45,012,000 $150,132,000 $27,492,000 $27,492,000 45.00% $126,225,333 $126,225,333 $38,625,333 $143,745,333 $21,105,333 $21,105,333 40.00% $118,242,000 $118,242,000 $30,642,000 $135,762,000 $13,122,000 $13,122,000 35.00% $107,977,714 $107,977,714 $20,377,714 $125,497,714 $2,857,714 $2,857,714 30.00% $94,292,000 $94,292,000 $6,692,000 $111,812,000 -$10,828,000 -$10,828,000 25.00% $75,132,000 $75,132,000 -$12,468,000 $92,652,000 -$29,988,000 -$29,988,000 20.00% $46,392,000 $46,392,000 -$41,208,000 $63,912,000 -$58,728,000 -$58,728,000 15.00% -$1,508,000 -$1,508,000 -$89,108,000 $16,012,000 -$106,628,000 -$106,628,000 10.00% -$97,308,000 -$97,308,000 -$184,908,000 -$79,788,000 -$202,428,000 -$202,428,000 5.00% -$384,708,000 -$384,708,000 -$472,308,000 -$367,188,000 -$489,828,000 -$489,828,000 Hence, based on the load factor, the company’s decision is taken. If we were to assume that the load is residential, and its load factor is more than 15.12%, then for sure it would be better to transfer excess power. If not, then buy it from PB.
  • 47. 40 2.4. Power Distribution This section goes over some of the technology activities done in the POD department. It starts with a detailed view of the UPS system, mentioning details about what it is, what are its types and applications, and then dives deeply to the On-Line Double Conversion UPS system by laying down its main application, process, components, and maintenance activities. Followingly, the same is done in power transformer in terms of showing its types, components and maintenance tests. It then outlines key information about low voltage breakers and finally gives a summary about protective relays, needed to understand Chapter 3. 2.4.1 Uninterruptible power supply An Uninterruptible power supply (UPS) is an apparatus used to maintain energy supply to loads, commonly in the case of a power outage. UPS Systems can be classified based on four main factors. Battery Capacity, to determine capability to supply the load. Power Conditioning, in which voltage supply is cleaned from fluctuation. Transfer time, the time it takes to transfer from primary supply to the battery. And finally Surge Protection, the technology used to protect the equipment from, for example, overloading and lighting. Based on these specifications, the three types of UPS systems are classified which are: Standby UPS system, Line-interactive UPS system, and Online Double Conversion UPS system. Three types of UPS System exist. First, the most basic form is the Standby UPS system. Simply, it uses AC power supply, and when a power outage occurs, the load receives energy from UPS’s battery. It does not have the Power Conditioning feature. However, it
  • 48. 41 can supply energy to small devices, specifically, ones with under 600 VA [22] consumption, e.g., printers, scanners, routers and other home or office devices. In addition, it takes 2-10 ms [22] to transfer the load, which means it is not a good option for critical loads, personal computers for example. Second, the line-interactive UPS system has the Power Conditioning feature; a built-in transformer is employed to decrease voltage fluctuations. Besides, it has a battery capacity that reaches up to 5 KVA [22]. The transfer time of the line-interactive UPS system is between 2 to 4 milliseconds, enough for critical loads. Finally, and most importantly, is the Online Double Conversion UPS System. The capacity of the batteries depends on user’s need. As will be shown later, the batteries for Aramco’s data centers reaches up to a 100 KVA, with a Transfer time less than 4 milliseconds [22]. Several layers of electronic components, filters and surge protectors, are used in removing electrical disturbances. It is important to note that any commercial UPS system must meet the following requirements [23] [24]: 1) It must have a constant steady state RMS voltage, with less than 2% variation in other parameters, e.g., load current. 2) No more than 10% peak transient voltage deviation is allowed in loading/unloading process. 3) The inverter output voltage shall not have more than 4% total harmonic distortion in all load conditions. 4) In 2 AC cycles, the voltage must not drop more than 5% of the rated voltage.
  • 49. 42 Next, the process of a UPS system is as follows, electricity is supplied and converted to DC using the rectifier. It is then converted back to a clean sinusoidal AC by the inverter. This is done to (1) isolate the load from frequency variation, (2) to clean voltage distortions before it is supplied, as critical loads are sensitive to these distortions, and (3) charge the batteries, since they cannot be charged with AC. The components of the Online Double Conversion UPS system are shown in Figure 16. Figure 16: Equipment of Online Double Conversion UPS System [25] UPS is operated in one of the three modes, namely, normal mode, bypass mode, and battery mode. Firstly, in normal mode, the UPS will operate as mentioned in the previous paragraph. It isolates the load and supplies it with clean sinusoid electricity. Secondly, bypass mode is activated when any fault occurs inside the UPS system. The transfer switch connects the load to the main supply directly through bypass line until the internal fault is fixed. Finally, any interruption to the primary power supply results in an automatic conversion to battery mode. In this mode, batteries feed the critical load through inverter. Whenever batteries’ energy is depleted, the UPS will check the status of Bypass line. If there is energy on the bypass, UPS will switch to the bypass line using the transfer switch.
  • 50. 43 Otherwise, UPS will issue a shutdown Imminent alarm. In case the AC power supply is back, UPS mode is switched back to the normal mode. Additionally, UPS consists of batteries, transfer switches, solid-state rectifier, and an inverter. Each of these components is discussed and depicted in the next several pages. 1) Batteries Lead-acid batteries are used in the UPS System due to their low cost, long lifespan ranging from 6 to 15 years [26], and reliable performance. Each package of Lead-acid batteries is connected in series to increase its total output voltage. Each battery, shown next page in Figure 17 is a 2.2 Volt battery, collectively having an output voltage of 240V. Each package of batteries is connected in parallel to increase their capacity. Utilizing all the packages, the UPS system has an output capacity of 100 KVA [27], with 0.9 Power factor. 2) Transfer Switch Transfer switch is an auto/manual switch to change UPS’s mode of operation, shown in Figure 18. For maintenance, specifically in minor preventive maintenance, the transfer switch is used to convert supply directly through the Bypass. However, in Major Preventive Maintenance, the isolation switch is used to shut down the UPS completely. 3) Rectifier Rectifier is used for two purposes, (1) to convert AC voltage into DC, and (2) to smooth and clear noise and spikes from voltage supply. Rectifier’s equipment are shown in the Figure 19. Control Fuses are used to protect the fans from faults, and Input Fuses protect
  • 51. 44 the Input Capacitors. Input Capacitors aid in smoothing input voltage. Rectifier’s Blower Fans cool down the rectifier, and the DC capacitors cleans output DC signal from distortions. Breaker is used to shutdown the rectifier when internal fault occures. 4) Inverter Inverter converts DC Voltage into AC. Its equipment are shown in Figure 20. The Remote Communcation Board is for communcating with an outside computer. The internal communcation board is for internal communcation between components of the Inverter. Figure 17: Batteries of the UPS System.
  • 52. 45 Figure 18: Representation of Transfer Switches
  • 53. 46 Figure 19: A Photograph of UPS Rectifier
  • 54. 47 Figure 20: Illustration of a UPS Inverter
  • 55. 48 The main application of a UPS system is elucidated in the following case. Whenever the input supply fails, critical loads receive energy from UPS. Servers of companies are a very good example of this. To elucidate the usefulness of using UPS system, assume the following case. When company servers are detached from electricity, all unsaved information is lost. In addition, all services within the company are discontinued. A disconnection time of 9ms may shutdown company’s servers. To prevent this problem, UPS system is installed for backup energy. Moreover, Alrashdi, foreman of the UPS unit in Power Operation Department, specified in a personal interview that batteries of the Online UPS system can supply energy to the Tower building of Aramco, a building with an average energy consumption of around 200 KWh, for possibly 30 minutes. At that time, another simple cycle generator is prepared to start supplying energy to the tower. Now with the maintenance activities. Technicians apply three types of maintenance: Inspection, Minor PM (Preventive maintenance), and Major PM. In Inspection, technicians visually inspect the UPS from outside, i.e., verify status screen of the UPS system. They also measure the voltage of 10% of the batteries of the UPS system. In other words, technicians measure at least three batteries for each battery package. The inspection is done on a weekly basis. In Minor PM, first, technicians measure the voltage and current of (1) receiving end of Inverter, (2) primary supply, and (3) measure all 24 batteries, of one package, and compare them to their normal operation case. Second, technicians visually check internal components of the UPS. Third, technicians use a thermo vision tool to inspect physical integrity of voltage supply cables, output feeders and ground connections. Finally,
  • 56. 49 technicians clean the filters of the UPS using air extractors. The Minor PM is done on quarterly basis. In Major PM, the above activities are all also completed. But before that, UPS System must be shut downed completely. In addition to the Minor PM activities, technicians examine the UPS capacitors, namely, Input and DC Capacitors, and replace them in case of any damage or leakage exists. More importantly, in Major PM, technicians test the control circuitry (the PCBs), and at the end, simulate an emergency case to verify the readiness of the UPS. 2.4.2 Power Transformer Power Transformer is a 3-phase, Delta – Y connected, bulky passive electromagnetic device used for HV (High Voltage) conversion, i.e., above 69 kV. The Power Transformer steps up or down HV, and is mainly used in power plants to decrease the current, thus, decrease the losses through transmission lines. One feature of Power transformer is its tap changer, to change the turn ratio by changing the tap of the secondary winding. Speaking about the components, Power Transformer consists of 13 components, shown partially inside Aramco’s workshop in Figures 21 and 22, and collectively in Figures 23 and 24. These are: 1) Main Tank, which contains insulated windings of the primary and secondary sides. 2) HV Bushing, similar to the suspension insulators, except that from inside, it contains a conductor, protected by an insulating material, to guard the HV cables feeding the Power Transformer. 3) LV (Low Voltage) Bushings, connected to the LV side of the transformer.
  • 57. 50 4) Radiator, used in dissipating the heat of the transformer. 5) Cooling fans, operated automatically by a Temperature Relay. 6) Conservator Tank, used to store excess oil from the Main Tank, because when the temperature of the transformer increases, the oil within the Main Tank expands and leaks. Thus, leaked oil is collected by the Conservator Tank 7) Ground Terminal, connected commonly to NGR (Neutral Ground Resistor), an enormous resistor used to dissipate electrical surges coming from, say, lightning. 8) Drain Valve, opened to let the oil flow out of the transformer. It is used for two reasons: (1) To take a sample for measuring multiple factors of the oil, insulation capability for example, and (2) to drain the oil tank when oil replacement is needed. 9) Dehydrating Breather, shown in Figure 24, is used to prevent moisture from entering the oil tanks of the transformer. 10) Oil Temperature and Pressure Gauges, measure and display temperature and pressure, in degrees Celsius and in kilo pascals, respectively. 11) Bushing Current Transformer, used to measure the current flowing through the winding, which is attached to the control panel for monitoring purpose. 12) Control Panel, where operations of the transformer are monitored and controlled both manually and automatically. 13) Tap changer, not shown in figures, used to change the turn ratio, ratio of turns between primary winding and secondary winding.
  • 58. 51 Figure 21: Left View of a Power Transformer Figure 22: Front View of a Power Transformer
  • 59. 52 Figure 23: Power Transformer Components [28]. Figure 24: Dehydrating Breather of Power Transformer [29].
  • 60. 53 Seven tests are applied to examine the performance of a Power Transformer. The purpose, method and expected results of the tests are discussed below. Insulation Resistance Test: This test measures insulation resistance of the oil around transformer’s winding. The bigger the resistance, the better the insulation. To perform the test, technicians connect an ohm meter as shown in Figure 25. Practically, the 3 HV bushings are shorted, and the 3 terminals of LV Buss Bar inside the transformer are also shorted. The positive terminal of Megger Insulation Tester is connected to the HV bushings, while the negative terminal is connected to the LV Buss Bar. Any value bigger than 1 Giga ohm is enough for passing the test. Failing in this test means the oil does not provide adequate insulation between the primary and secondary windings. It is worth noting that insulation insulates magnetic field based on its frequency. A low frequency magnetic field is not attenuated by oil insulation. However, a high frequency magnetic field is attenuated. That is why oil in transformers does not insulate the magnetic field of the windings from each other, and at the same time, does not create a short circuit between them. Turn Ratio Test: This test examines the voltage of different taps of the transformer. It is then compared to transformer’s nameplate. To perform the test, 10 KV is supplied to primary side of the transformer through HV bushings, while the stepped down voltage is measured from LV Buss Bar. The results are then scaled and compared to the nameplate. The taps are considered in good condition only if the percentage difference between nameplate and current measurement does not exceed 5%.
  • 61. 54 Figure 25: Connection of Insulation Resistance Test [30] Winding Resistance Test: Opposite to the insulation resistance test, this test measures the conductivity of the winding. Winding Resistance Test is performed though measuring the resistance of all 6 windings, since Power Transformer is a 3-phase device. Less resistance of winding means better conduction. Typically, the resistance of the winding is less than 20 mΩ. Result of this test can indicate if any cut in the winding wire exists. Bushing Test: This test evaluates the physical integrity of the bushings. This test is carried out by connecting the positive terminal of M7100, to the primary capacitor (Upward part of the bushing) and negative terminal of the device to the ground. Repeated for phases A,B,C. and then positive side of M7100 to secondary capacitor (Downward part of the bushing) and negative side to the ground. Repeated for phases A,B,C. The transformer condition is considered good only if the power factor of the bushing is less than 0.5%.
  • 62. 55 Surge Arrester Test: This test measures the insulation strength of surge arresters. This is done by providing 50% of rated voltage of the arrester, and measuring the current that flows through the arrester. The test must be carried out with consistency. For that reason, technicians apply the same test voltage for the same amount each time, optimally 60 seconds. This test is repeated 3 times. The average reading is taken as the result. A repeatable result is indicative of a good measurement process. Sweep Frequency Response Analysis Test (SFRA): SFRA assesses the mechanical integrity of transformer’s components, the core and winding for example. This test is performed by sending signals of different discrete frequencies to the winding, and measuring the returning signal. Results are graphed and compared to the older results. A difference between the current and old results means a component has been displaced. Example of SFRA graphical result is shown below in Figure 26, with a curve for each phase of a transformer. Figure 26: Example of an SFRA Test Measurement [31]
  • 63. 56 Oil Analysis Test: This is a diagnostic test to determine the condition of transformer oil. A sample is taken via Drain Valve, and is sent to the laboratory for analysis. Various parameters are analyzed, including oxidation stability, thermal stability, viscosity, conductivity, acidity, color, moisture content, etc. measurement of these parameters may reveal the causes of common problems in the Power Transformer, overheating and arcing for instance. 2.4.3 Low Voltage Breakers To provide control and protection for different large equipment, like generators, transformers or motors, circuit breakers are used as a safeguard to defend personnel and equipment from abnormal conditions. Circuit breakers control the flow of current, by interrupting the circuit when extreme current is reached. There are three main types of low voltage breakers that are used in industrial, commercial, and residential buildings, which are: Miniature Circuit Breakers (MCBs), Molded Case Circuit Breakers (MCCBs), and Residual Current Circuit Breakers (RCCBs). MCB are widely used in residential and commercial constructions. They are compact devices designed to safeguard electrical circuits from short circuits or overloads. The M (Miniature) means the breaker is smaller than the other breaker types. MCCBs, on the other hand, are a more robust version of MCBs. MCCBs can endure a greater amount of current, and are commonly found in industrial and large-scale facilities. The MC (Molded Case) refers to the breaker’s components being housed inside a highly durable and insulating casing, preventing the current from leaking. Finally, RCCBs, sometimes referred to as Ground Fault Circuit Breakers (GFCI), detect imbalances between live and neutral currents. They are specialized in guarding against ground faults. RCCBs are typically found in houses,
  • 64. 57 specifically, inside breaker panels. The three breaker types are shown in Figure 27. Typically, MCB is combined with RCB in practical applications, such as the one in Figure 28, where the main switch is an MCB. Figure 27: An illustration of MCB, MCCB and RCCB, respectively (raw image sources: [32][33][34]). Figure 28: A Photograph of a Breaker Panel [35].
  • 65. 58 2.4.4 Protective Relays To ensure safety and reliability, protection relays are used to shield personnel and equipment from hazardous damage, caused by uncontrolled short circuits. The main function of a protective relay is to operate the trip circuit quickly, specifically in the fault area, while the rest of the system stays unaffected. Protective relays are most likely installed within a switchgear, to detect abnormal conditions and activate its breakers. Protection relays are characterized by four requirements, which are: Discrimination, Coordination, Reliability and Speed of Operation. First, Discrimination is the relay’s ability to discriminate between a normal overload, as what happens in noon when the weather is too hot, to a heavy overload, caused for example by faults. Second, Coordination is relay’s ability to be selective, that is, the relay only disconnects the output feeder having the fault, without affecting input feeders. The reader can better understand this by referring to Figure 29, where white boxes represent closed breakers, and red ones represent open breakers. Figure 29: An Illustration of Coordination Characteristic.
  • 66. 59 Thirdly, Reliability is the probability of a relay to work with no failure. Good practices in manufacturing the relays heavily contribute to reliability. Also, regular maintenance and excellent design reduce the probability of failure. Finally, Speed of Operation must be rapid. As will be shown later in the second case study, electromagnetic relay is able to trip the circuit in less than quarter of a second. This is essential to avoid injuries to personnel, as well as damaging equipment. ANSI Standard Device Number is used in naming the different types of relays. A number is assigned to each type of relay. This is to simplify the one-line diagram by saving space and text. Modern electronic protective relays may have multiple ANSI numbers when they have multiple functions. The ANSI Standard Device Number is shown in Figures 30 and 31. The most common types of relays are demonstrated in Table 17, with their main application.
  • 67. 60 Figure 30: First Page of ANSI Standard Device Number [36].
  • 68. 61 Figure 31: Second Page of ANSI Standard Device Number [36].
  • 69. 62 Table 17: Most Common ANSI Device Numbers ANSI Number Application ANSI Number Application 25 Synchronizing and Synchronism- check Device After synchronizing its voltage and frequency, the device closes a breaker that connect a generator to a live bus. 51 AC Time Overcurrent Relay This relay trips when a predetermined time and current has been reached. The time setting can be definite, that is, no matter whether 1 A flowed in the relay or 10A, the tripping time remains the same. Conversely, an inverse time setting can be used to decrease the trip time as the current increases. 27 Undervoltage Relay Monitor the voltage of an electrical system. The relay can either energize alarm or trip the circuit in the case of an undervoltage. 52 AC Circuit Breaker A breaker that is controlled by relays 32 Directional Relay Monitor the direction of current. In DC circuit, the relay trips after exceeding a certain level of reverse polarity. However, in AC circuits, the relay trips based on the power factor of the load, for example, when a severe lagging power factor is detected. 59 Overvoltage Relay Overvoltage relay has a similar function to overcurrent relays. This relay is designed to trip in the case of overvoltage spikes. 40 Loss of Field Relay Observe the excitation level of a generator using a coil, which is connected in series with generator field, and trips when the field drop beyond setpoint. 64 Ground Detector Relay This relay functions on the failure of insulation of, e.g., in transformers, machines or other apparatus. In other words, the relay will operate when the surface of an insulator becomes conductive, causing a ground fault. 50 Instantaneous Overcurrent Relay Upon excessive current, or on excessive rate of rise in current, is reached, the overcurrent relay will trip the associated breaker instantly.
  • 70. 63 The remaining subject will summarize the details of the Electromagnetic relays. This is done for the reader to be able to understand the case study discussed in Chapter 3. Electromechanical relays are categorized by their use to one of two basic operating mechanisms, which are: Electromagnetic attraction relays, and Electromagnetic induction relays. An electromagnetic attraction relay is an electromagnet made from solenoid. This type of relay is usually operated to activate the trip circuit inside a breaker. The other type of electromagnetic attraction relay is a one that attracts hinged armature, to open or close a set of contacts. Both types of electromagnetic attraction relay are identified by number 50, based on ANSI numbering system. These electromagnetic relays are instantaneous pick-up, meaning that they do not have the time delay feature. They can work for both DC and AC. The instantaneous relay setting is adjustable, allowing user to regulate the amount of current at which the relay picks-up. In a switchgear’s protection relay, this value is set precisely. In case the monitored current is smaller than 4A, or higher than 144 A, a current transformer is used to change the value of current to something within that current range. The instantaneous relay tap settings are shown in Figure 32-D. The tap plug can be moved to choose the range of current, while the screw is for precise calibration. Induction relay, which is the second type of electromagnetic relays, operates like an induction motor. The moving element, called metal disk, rotates on a shaft, as shown in Figure 32-B, while the stationary coil senses the overcurrent or fault current. The induction relay provides the time delay feature, which can be a definite-time or inverse-time type, as clarified in Table 18, ANSI #51.
  • 71. 64 When the station coil is energized, current is induced to the metal disk to make it turn against restraining spring to provide the time delay trip. The movable contact moves toward the stationary contact at a speed proportional to the current flow in the coil. When the two contacts touch each other, the auxiliary trip coil or breaker trip coil is energized. Multiple coils can be used to vary the induction relay’s sensitivity to voltage and current. The coil can be additive, or subtractive, that is they work together, or against each other. Induction relays have very accurate pickup and time current response, as explained next in Chapter 3.
  • 72. 65 4 A B C D Figure 32: Components of a CO-9 Electromagnetic Relay A A B B C C D D
  • 73. 66 CHAPTER 3: CASE STUDY I - ELECTROMAGNETIC RELAY TEST 3.1. Introduction On 17th of March, an unexpected power outage occurred to a facility. The power meter was reviewed, and no sudden current was found. However, it was expected later that the CO-9 Electromagnetic Relay installed in the protection system was the cause of this issue. For this reason, the CO-9 Electromagnetic Relay was taken to the laboratory to be tested. Therefore, this case study examines the healthiness of the CO-9 Electromagnetic Relay. 3.2. Methodology A quantitative methodology was employed in this case study; it is to test the three main parts of a CO-9 Electromagnetic Relay, namely, Instantaneous Relay Coil, Time Dial, and the Current Tap Settings, which are shown in Figure 32-D, Figure 32-A and Figure 32-C, respectively. This test is done by varying the three parameters separately, and comparing the results to the characteristic curve of the CO-9 Electromagnetic Relay, shown in Figure 33. In the figure, the x-axis shows the Multiples of Tap Value Current (MTVC), that is, the ratio between testing current, injected to test the equipment, to the Current Tap Settings, which is the current threshold. For instance, with 2A of current threshold, an injection current of 4A results in MTVC to be 2. On the y-axis is the trip time. The more MTVC is injected, the less time it takes the relay to trip. The tripping action will start only if the MTVC is larger than 1.5. The series of trendlines shown in the figure are dependent on Time Dial, or in other words, the time delay. The reader can notice that these series of trendlines are only shifted versions of each other.
  • 74. 67 Figure 33: CO-9 Magnetic Relay Characteristic Curve [37] Megger SVERKER 750, a relay test unit, was used to examine the electromagnetic relay. This testing equipment is shown in Figure 34. Also, the connections of SVERKER 750 to the electromagnetic Relay is depicted, separately, in Figures 35 and 36, respectively. It is worth noting that the connection is the same for all the three tests.
  • 75. 68 Figure 34: A Photograph of the Megger SVERKER 750 [38] Figure 35: Connection of SVERKER 750 Figure 36: Connection of CO-9 Relay Figure 35: Connection of SVERKER 750 Figure 35: Connection of SVERKER 750 Figure 36: Connection of CO-9 Relay Figure 36: Connection of CO-9 Relay
  • 76. 69 3.3. Findings After injecting current and varying the Time Dial, the following results were obtained. Injected Current Multiples (MTVC) Time Delay (s) Current Threshold (A) Ideal Trip Time (s) Practical Trip Time (s) % Error x2 1 1 1.4 1.434 2.43% 2 2.7 2.811 4.11% 3 4 4.237 5.93% 4 5.7 5.674 0.46% 5 7 7.188 2.69% Table 18: Results of Time Dial Test Next, the Instantaneous Relay Coil setting was tested, and the results were as demonstrated in Table 19. Injected Current Multiples (MTVC) Time Delay (s) Current Threshold (A) Ideal Trip Time (s) Practical Trip Time (s) % Error x2 1 1 1.4 1.474 5.29% x3 0.6 0.613 2.17% x4 0.35 0.371 6.00% x5 0.25 0.276 10.40% x6 0.2 0.238 19.00% Table 19: Results of Instantaneous Relay Coil Test Finally, the Current Tap Settings were tested, and the results were as found in Table 20. Injected Current Multiples (MTVC) Time Delay (s) Current Threshold (A) Ideal Trip Time (s) Practical Trip Time (s) % Error x2 1 1 1.4 1.409 0.64% 2 1.4 1.417 1.21% 3 1.4 1.396 0.29% 4 1.4 1.358 3.00% 5 1.4 1.313 6.21% 6 1.4 1.281 8.50% Table 20: Results of Current Tap Setting Test
  • 77. 70 3.4. Analysis In order for the CO-9 Electromagnetic Relay to pass the test, it must score an error percentage below 5%. Failing to do so indicates that the equipment is faulty. Furthermore, on average, the error percentages of the CO-9 Relay’s for the following components, namely, the Time Dial, Instantaneous Relay Coil and Current Threshold, were 3.12%, 8.57% and 3.31%, respectively. Upon examining the measured results, it becomes evident that our initial expectation about corruption of CO-9 Electromagnetic Relay was valid. The Instantaneous Relay Coil was not working as anticipated. The Error percentage was escalating significantly as MTVC increases. Moreover, for the Current Tap Settings test, the trip time is supposed to remain constant as the current threshold increases. However, the obtained results indicate that the tripping time was inexplicably decreasing. Collectively, the abnormal function of the two components could be the reason for the power outage issue. 3.5. Conclusion The CO-9 Electromagnetic Relay failed the test. The two components, namely, Time Dial and Instantaneous Relay Coil were not functioning as expected, with the latter exceeding the limit of %Error. The following recommendations were proposed: 1) Conduct an inspection to all the protection relays that are installed within the same switchgear. 2) In case any relay is tested and proven to be corrupted, replace immediately.
  • 78. 71 CHAPTER 4: CASE STUDY II - POWER OUTAGE IN POD 4.1. Introduction The central issue of this case study is to analyze the power outages in the POD department taking place on the 2nd and 3rd of January 2023. A qualitative approach was followed in this case study; it is to inspect for defective equipment in the area fed by the tripped breaker. This case study will investigate, analyze and establish solution for the causes of the power outage occurred to the POD. 4.2. First Case At 3:46 PM, 2nd of January, the Air Circuit Breaker feeding the 13.8 kV overhead line, and eventually feeding POD buildings, was tripped by a neutral time overcurrent relay. Power was restored after 26 minutes by closing the tie breaker, a breaker that is closed only to supply energy from a secondary (emergency) source. The bus feeding the POD area was sectionalized in order to troubleshoot and find the source of the electric fault. After investigation, a spark was noticed on the insulator, located on a wooden electric pole. The defective insulator was replaced, and the power was restored. 4.3. Second Case The day after, on the 3rd of January, at 11:41 AM, the Air Circuit Breaker feeding POD buildings was tripped again by the overcurrent relay. Power was restored after 6 minutes. The bus was sectionalized, and the troubleshooting process started. This time, a blown surge arrester was found on the same wooden electric pole. The pole was isolated, and the surge arrester was replaced, and finally the power was back to normal.
  • 79. 72 4.4. Analysis For the first case, due to the rainy and windy weather conditions, the behavior of the porcelain insulator overturned, causing a leakage current to flow through the insulator surface. To explicate, when the insulator current encounters water, it generates heat that increases water’s temperature. This rise in temperature causes a localized area to be dry, forming what is called a dry band. Because of this dry band, high voltage electrons jump through the dry band, seen in the form of a spark, as depicted in Figure 38. These sparks, commonly known as arc discharges, damage the insulator and cause eventually a failure to it. Upon the failure of the insulator, a chain reaction is triggered, progressing to pollution flashover. During this phenomenon, the electrical stress exceeds the insulator’s ability to resist it, leading to a breakdown of the insulator, and afterwards activating the main breaker to trip and prevent further damage on the system. This process is summarized in Figure 37. Figure 37: Pollution Flashover Progression of insulators [39].
  • 80. 73 Figure 38: The Process of Contamination Discharge on Polluted Insulators [40]. Weather was not the only cause of the breaker trip. Further investigation revealed that the damaged insulator had only 432 mm of creepage distance, which does not comply with Saudi Aramco standard. According to Aramco’s standard, for each 1 KV, the insulator must have at least 40 mm creepage distance. In other words, for a 13.8 KV line, it must have a minimum of 552 mm creepage distance. Regarding the second case, after investigation, the surge arrester meets the IEC 99-4 standard, having specifications of 10 KA peak current, 12 KV continuous voltage, 15 KV residual voltage and with a hypered air-dielectric construction. In addition, the NGR
  • 81. 74 (Neutral Ground Resistor) was properly sized, with a rating of 1000 A, and therefore NGR was not the reason for failure. The reason for the failure is probably due to the improper grounding of the surge arrester, causing the current to circulate and eventually blow up the surge arrester. Moreover, the tripping of the main breaker feeding the POD area, instead of the one that feeds the zone of the blown surge arrester was investigated. It was found later that there were incorrect settings in the ground relay. The settings were corrected, and the case was closed. 4.5. Conclusion In this case study, an investigation was carried out to find the root causes of the power outage that occurred in the Power Operation Department (POD). The causes of the issue were due to a burned insulator, followed by a burned surge arrester. The two components were replaced, and suggestions and recommendations were made to avoid future trips of the main breaker. The following recommendations were suggested in this case study. 1) Immediately replace the defective insulators 2) Immediately replace the failed surge arrester 3) By July, 2023, ensure that all installed insulators in the POD area comply with the creepage distance standard, 40 mm for 1 KV, line to line. 4) By July, 2023, survey the feeder and find the number of porcelain insulators exist in the POD area, to be replaced with polymer insulators.
  • 82. 75 CHAPTER 5: CASE STUDY III - METERS’ CORRECTION FACTOR 5.1. Introduction In 2020, an agreement between Aramco and SEC was reached, allowing Aramco to supply energy to its offsite facilities through the national grid. Two types of meters were installed based on this agreement, Main meters and Check meters. The Main meters are owned by SEC and are used as the primary source of measurements, to be employed in calculating the demand invoice. On the other side, Check meters are owned by Aramco and are used as a secondary source for checking measurements. Main meters are installed in SEC substations, while Check meters are installed in Aramco facilities. A transmission line, ranging from 300 meters up to 13 Kilometers, connect between the two meters. Due to this transmission line, some of the electric energy is converted to thermal energy as it goes from main meter to check meter, meaning that, the two meters do not read the same value. A slight difference shows up between the two meters. That difference between the two meters is called Tie-line losses. Because of that, a correction factor shall be established as shown below, 𝑀𝑎𝑖𝑛 𝑀𝑒𝑡𝑒𝑟 = 𝐶ℎ𝑒𝑐𝑘 𝑀𝑒𝑡𝑒𝑟 × 𝐶𝑜𝑟𝑟𝑒𝑐𝑡𝑖𝑜𝑛 𝐹𝑎𝑐𝑡𝑜𝑟 (5.1) Whenever a power outage occurs to any of the Main meters, a correction factor will be used to be approximate Main meter using Check meter. As agreed upon, it is Aramco’s responsibility to establish the correction factor. Therefore, this case study will determine a relation between the Main meter and Check Meter.