JIMMA UNIVERSITY
JIMMA INSTITUTE OF TECHNOLOGY
FACULTY OF ELECTRICAL AND COMPUTER ENGINEERING
OVERALL INTERNSHIP EXPIRIENCE
AND PROJECT CARRIED ON
INTERNSHIP HOSTING COMPONY:
GEFERSA SUBSTATION
DONE BY:
NAME STREAM
1. HIKA TARIKU POWER
2. IBSA GEMECHU POWER
3. DAWIT GEBUL POWER
4. RAJI TSEGAYE POWER
5. ABDELA INDRIS CONTROL
6. TOLE YOSEPH CONTROL

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DECLARATION
This paper contains our overall internship experience and project carried on depending on the
problem identified during our internship duration. The project is entitled as Digital Metering
System of Oil level and Temperature of Transformer. We declare that what we have done is
our original work. We have not copied from any other sources except where due to reference or
acknowledgement is made explicitly in the text, nor has any part been written for us by another
person. All relevant resources of information used in this paper have been duly acknowledged.

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ACKNOWLEDGEMENT
First and foremost, we would like to express our heart full gratitude to Faculty of Electrical and
Computer Engineering for giving us the chance of practicing a project supported with our
theoretical knowledges of existing realities. Secondly, we would like to express our earnest
gratitude and regards to our advisor Dr. Tefera in the Faculty of Electrical and Computer
Engineering, for being the corner stone of our project and also for the workers of Gefersa
substation for the knowledge they have been sharing for us and answering for our question as
much as possible without hesitating. It was their perpetual motivation and guidance during the
period of doubts and uncertainties that has helped us to carry on with this internship program.
Finally, we extend our gratefulness to one and all who are directly or indirectly involved in the
successful completion of this project work.

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Table of Contents
DECLARATION............................................................................................................................I
ACKNOWLEDGEMENT............................................................................................................II
LIST OF FIGURES....................................................................................................................VI
LIST OF TABLES................................................................................................................... VIII
ACRONYM .................................................................................................................................IX
ABSTRACT.................................................................................................................................. X
CHAPTER ONE ........................................................................................................................... 1
INTRODUCTION......................................................................................................................... 1
1.1 Background.......................................................................................................................... 1
1.2 Substation............................................................................................................................. 2
1.2.1 Service requirement...................................................................................................... 2
1.2.2 According to the constructional feature...................................................................... 2
1.3 Gefersa Substations Establishment.................................................................................... 2
1.4 Mission and Vision of Gefersa Substation......................................................................... 3
1.4.1 Mission of Gefersa Substation...................................................................................... 3
1.4.2 Vision of Gefersa Substation........................................................................................ 3
1.5 Main product or service...................................................................................................... 4
1.5.1 Main product ................................................................................................................. 4
1.5.2 Main service................................................................................................................... 4
1.6 Overall Organization and Workflow................................................................................. 4
CHAPTER TWO .......................................................................................................................... 5
OVERALL INTERNSHIP EXPERIENCE................................................................................ 5
2.1 Section of The Substation.................................................................................................... 5
2.1.1 Outdoor Substation....................................................................................................... 5
2.1.2 Indoor Substation........................................................................................................ 14
2.3 Job Ethics ........................................................................................................................... 17
2.4 Challenges We Have Been Facing and How We Have Overcome Them ..................... 18
2.5 Single Line Diagram of Gefersa Substation.................................................................... 19
CHAPTER THREE.................................................................................................................... 20
OVERALL BENEFIT GAINED ............................................................................................... 20

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3.1 Improving Our Practical Skills ........................................................................................ 20
3.2 In Terms of New Theoretical Knowledge Acquired....................................................... 20
3.3 New Training We Have Taken......................................................................................... 21
3.4 In Improving our Inter-personal Communication Skill and Team Work................... 21
3.5 In Terms of Understanding About Work Ethics and Related Issues ........................... 21
CHAPTER FOUR....................................................................................................................... 23
BACKGROUND ......................................................................................................................... 23
4.1 Introduction ....................................................................................................................... 23
4.2 Statement of Problem and Proposed Solution ................................................................ 24
4.2.1 Statement of Problem.................................................................................................. 24
4.2.2 Proposed Solution........................................................................................................ 24
4.3 Literature Review.............................................................................................................. 24
4.4 Objective............................................................................................................................. 25
4.4.1 General Objective........................................................................................................ 25
1.4.2 Specific Objective........................................................................................................ 25
4.5 Significance and Scope of The Project............................................................................. 26
CHAPTER FIVE ........................................................................................................................ 26
METHODOLOGY ..................................................................................................................... 26
5.1 Block Diagram of The Project.......................................................................................... 26
5.2 Design Procedure............................................................................................................... 27
5.3 Hardware Requirement .................................................................................................... 28
5.3.1 Arduino Uno ................................................................................................................ 28
5.3.2 Ultrasonic Sensor......................................................................................................... 29
5.3.3 RTD-PT100.................................................................................................................. 30
5.3.4 Operational Amplifier ................................................................................................ 31
5.3.5 LCD .............................................................................................................................. 32
5.3.6 Resistor......................................................................................................................... 32
5.3.6 Transformer................................................................................................................. 33
5.3.6 Rectifier........................................................................................................................ 34
5.3.7 Filtering Capacitor...................................................................................................... 35
5.3.8 Voltage Regulator........................................................................................................ 36

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5.4 Software Requirement ...................................................................................................... 37
5.4.1 Arduino IDE ................................................................................................................ 37
5.4.2 Proteus Professional.................................................................................................... 37
5.4.3 Draw.io Software......................................................................................................... 37
5.4.4 PAINT 3D software..................................................................................................... 38
5.4.5 ETAP Software............................................................................................................ 38
5.5 Flow Chart.......................................................................................................................... 39
CHAPTER SIX ........................................................................................................................... 40
RESULT AND DISCUSSION ................................................................................................... 40
6.1 Power Supply ..................................................................................................................... 40
6.2 The Overall Diagram of the system ................................................................................. 40
6.3 Measured Values................................................................................................................ 42
CHAPTER SEVEN..................................................................................................................... 44
CONCLUSION AND RECOMMENDATION........................................................................ 44
7.1 Conclusion.......................................................................................................................... 44
7.2 Recommendation ............................................................................................................... 45
REFERENCE.............................................................................................................................. 46
APPENDIX I ............................................................................................................................... 47
Algorithm ................................................................................................................................. 47

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LIST OF FIGURES
Figure 2. 1 wave Trap ..................................................................................................................... 5
Figure 2. 2 Surge Arrestor .............................................................................................................. 7
Figure 2. 3 [A] Auto and [B] Power Transformer .......................................................................... 8
Figure 2. 4 Conservator................................................................................................................... 8
Figure 2. 5 Silica gel ....................................................................................................................... 8
Figure 2. 6 Buchholz relay.............................................................................................................. 9
Figure 2. 7 Radiator and fan ........................................................................................................... 9
Figure 2. 8 Tap changer ................................................................................................................ 10
Figure 2. 9 Voltage Transformer .................................................................................................. 12
Figure 2. 10 Current Transformer................................................................................................. 12
Figure 2. 11 Disconnector (isolator) ............................................................................................. 13
Figure 2. 12 Busbar Coupler......................................................................................................... 13
Figure 2. 13 [A] Vertical and [B] Horizontal Circuit Breaker...................................................... 14
Figure 2. 14 Protection Panel........................................................................................................ 15
Figure 2. 15 [A] Battery Cell and [B] Rectifier............................................................................ 15
Figure 2. 16 Single line diagram of gefersa substation................................................................. 19
Figure 5. 1 Block Diagram of the project ..................................................................................... 27
Figure 5. 2 Arduino Uno............................................................................................................... 29
Figure 5. 3 Ultrasonic Sensor........................................................................................................ 29
Figure 5. 4 illustration of ultrasonic sensor mounting .................................................................. 30
Figure 5. 5 RTD PT100 ................................................................................................................ 31
Figure 5. 6 Operation Amplifier ................................................................................................... 32
Figure 5. 7 LCD ............................................................................................................................ 32
Figure 5. 8 A(Constant resistor), B (Variable resistor)................................................................. 33
Figure 5. 9 Step-down Transformer.............................................................................................. 34
Figure 5. 10 Rectifier .................................................................................................................... 34
Figure 5. 11 signal A) after and B) before filtering capacitor ...................................................... 36
Figure 5. 12 Voltage Regulator..................................................................................................... 37
Figure 5. 13 Flow Chart................................................................................................................ 39
Figure 6. 1 Power Supply.............................................................................................................. 40

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Figure 6. 2 The Overall Diagram of The System.......................................................................... 41
Figure 6. 3 LCD displays with in 1 second difference ................................................................. 42
Figure 6. 4 The values of temperature before five second............................................................ 43
Figure 6. 5 The values of temperature after five second............................................................... 43

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LIST OF TABLES
Table 2. 1 some information of power transformer ...................................................................... 10

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ACRONYM
AC ……………………… Alternating current
CB ……………………… Circuit breaker
CT ………………………. Current transformer
DC ………………………. Direct current
EEP ………………………. Ethiopian Electric Power
EEPCo ………………………. Ethiopian Electric Power Corporation
EEU ……………………… Ethiopian Electric Utility
Hz ……………………… Hertz
IC ……………………… Integrated circuit
ICSP ……………………. In-circuit serial programming
IDE ……………………. Integrated developmental environment
IOREF ……………………… Input output voltage reference
KV ………………………. Kilo Volt
LCD ………………….…… Liquid crystal display
LDC ……………………… Load Despise center
LDR ………………………… Light Dependent Resistance
MW ………………………… Mega Watt
MVA ………………………… Mega Volt Ampere
ONAN ……………………… Oil Natural Air Natural
ONAF ……………………… Oil Natural Air Forced
PRT ………………………. Platinum Resistance Temperature
PT ………………………. Potential Transformer
PIC ………………………. peripheral interface control
PWM ………………….…… pulse width modulation
SCADA ………………………. Supervisory Control and Data Acquisition
Y/D …………………………... Star/Delta
Y/Y …………………………. Star/Star
USB ……………………… Universal serial bus

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ABSTRACT
This report has been made based on internship program we had in Gefersa substation. The report
has two parts. The first part is the overall internship experience and includes the substations history
starting from the year the substation has been stablished or background, mission and vision of the
substation in future and the main product of the substation. Additionally, the section of the
substation which includes roughly the equipment installed inside substations, tasks that have been
executed during our duration, challenge faced and job ethics we have learned and overall benefit
gained throughout the internship program either new theoretical knowledge or practical skill we
have improved. The second part is the project carried out. The substation has its own protection
system for transformer from the fault like overheating, phase-to-phase fault, over-load fault,
insulation failure fault, inter-turn fault and earth fault. So, they do not have a problem with
protecting transformer to be safe. But, whenever the alarming system or protection device
discussed above are malfunction for some reason, any significant fault scenario can damage the
transformer. So, the reading on the transformer such as oil level, winding temperature and tap
changer have to be displayed digitally so as to make the recorded data clear and accurate for the
safety of the transformer. But for the transformer part, the substations use analog metering system
to measure oil level and temperature for both auto transformer and power transformer. The
metering device are mounted on the transformer. Since then, the reading meter might not be seen
accurately due to weather condition and moisture could also make it invisible to read the reading.
Additionally, it is tiresome for the workers of the substation to go out to read the above parameters
from the transformers. This problem has been solved by using Arduino microcontroller and the
project is tilted as “digital metering system for temperature and oil level of transformer”. The
project has no implementation and tested by using simulation software called proteus professional.

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PART ONE
OVERALL INTERNSHIP EXPIRIENCE

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CHAPTER ONE
INTRODUCTION
1.1 Background
Electric power can be transmitted or distributed either by means of overhead or underground. The
underground cables are rarely used for power transmission due to two main reasons. Firstly, power
is generally transmitted over long distances to load centers and the cost of installation become too
high. Secondly, electric power has to be transmitted at high voltages for economic reasons and it
is very difficult to provide proper installation for cables to withstand such high pressure. Therefore,
power transmission over long distances is carried out by using overhead lines. An overhead line is
subjected to uncertain weather conditions and other external interferences. This calls for the use
of proper mechanical factors of safety in order to ensure the continuity of operation in the line. In
general, the strength of the line should be such so as to provide against the worst probable weather
conditions. The successful operation of an overhead line depends to a great extent upon the
mechanical design of the line. While constructing an overhead line, it should be ensured that
mechanical strength of the line is such so as to provide against the most probable weather
conditions. The main components of an overhead line are conductors, supports, insulators, cross
arm and miscellaneous item [1]. The power generated from the generation station has to be
transmitted to distribute it to consumers and this has to be organized to make the distribution as
clear and adequate as much as possible. To provide adequate and quality electricity generation and
transmission, there should be improved management that is responsive to socio-economic
development and environmental protection. The Ethiopian Electric Light and Power Authority
(EELPA) which was established in 1949, after having underground restructuring was organized as
Ethiopian Electric Power Corporation (EEPCo). But later on, EEPCo split into two companies
called Ethiopian Electric Power (EEP) and Ethiopian Electric Utility (EEU). EEP which was
established in 2006 according to Ethiopian calendar is responsible for generating, transmitting,
and wholesale electricity to be utilized nationwide as well as in neighboring countries and also for
feasibility study, survey, and design. Regarding power generation plants, currently Ethiopian
electric power administers 18 power plants thereby generating a total of more than 4244 MW of
electricity nationwide. Among these 18 power plants, 14 are hydropower plants and it has a
generating capacity of 3814MW except Hidase [2].

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1.2 Substation
The assembly of apparatus used to change some characteristics of power systems parameters is
called substation. The substation can be classified based on:
1.2.1 Service requirement
According to service requirements, the substation can be classified as
1. Transformer substation which changes the level of voltage either to step up or step
down.
2. Switching substation which is used for switching operation (the level of voltage is the
same)
3. Power factor correction substation which is used to give correction on power factor
within the given tolerance.
4. Converting substation which is used to change ac to dc or the reverse.
5. Frequency changer substation which is used to protect the frequency of the power
system within the required tolerance.
6. Industrial substation which supplies power to industries
1.2.2 According to the constructional feature
1. The indoor substation is a substation where the equipment is installed indoors because
of economic considerations (applied for a voltage less than 11kv and this voltage can be
erected up to 66kv if there I impure weather conditions).
2. The outdoor substation is where the equipment is installed outdoors (especially for a
voltage above 66kv).
3. Underground substation is usually used in thickly populated areas for the economic
consideration of lands and though the substation is built underground.
4. Pole mounted substation is an outdoor substation with equipment installed overhead.
There are around 163 substations in Ethiopia ranging from 132kv to 500kv [3].
1.3 Gefersa Substations Establishment
Gefersa substation has been established in 1958 and the input to the system during that time was
only from the Kaliti substation with 132kv (which is from Awash and Koka generation stations).
It is located in Burayu which is special zone surrounding Finfinne in oromia region. The substation
started with only one power transformer which was 3 winding and there was only 15kv with one
feeder which was distributed to Gefersa and Asko (two 15kv from the feeder) and one 45kv which

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goes to Addisalem. The rating of the transformer was 12MVA. Then Ghedo 1 which is from Fincha
generation station entered the substation in 1965 with 230kv with four autotransformers which is
rated 40MVA each and in 1997, they installed 125MVA rating autotransformer. In 1994 Sebeta,
1999 Sululta 1, and Sululta 2 has become an input to the substation, and later on, in 2000, Ghedo
2 and Ghedo 3 are added. It is also known as ring type substation since it can send to substations,
industries, and householders and receive from another substation. There are six different input
lines which are 230kv to this substation such as Ghedo1, Sebeta, Ghedo2, Ghedo3, Sululta1, and
Sululta2. All six lines are transported by using the steal tower. Interestingly, they had been using
the transmission line for communication purposes by using a device called a wave trap in order to
filter high-frequency signals (which is a communication signal) from low-frequency (power
signals). The substation has also been using an air blast type circuit breaker and it was a hard and
tiresome task to fill the air to the breaker. But now they are using SF6 type circuit breaker. There
are two sections called switch yard and control room in this substation. The switch yard consists
of different equipment such as an insulator, wave trap, conductor, steal towers, transformer (both
potential and instrument transformer), busbar (both pipe type and conductor type), circuit breaker
(SF6 CB), bus coupler and isolator or disconnector. There are four auto transformers all with a
125MVA rating which have the capability of stepping 230kv down to 132kv. There are also four
core-type power transformers. Out of these four transformers, three are 3 winding and only one is
2 winding. The control room consists control and protection panel from which all the parameters
are to be recorded such as relays, energy meter (digital energy meter), different alarming systems,
and also different equipment which are used to power up the equipment in the substation only such
as auxiliary power transformer(15kv/220v), battery cell and generators.
1.4 Mission and Vision of Gefersa Substation
1.4.1 Mission of Gefersa Substation
To provide adequate and quality electricity from the power transmitted to the station through
continuous improvement of management to local consumers (household consumers), industries,
and other substations.
1.4.2 Vision of Gefersa Substation
To be an effective and efficient substation by having high-quality management for the laborers
and customers and also providing reliable electricity to users.

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1.5 Main product or service
1.5.1 Main product
On the other hand, that six-input line which is 230kv stepped down to 132kv and further to 66kv,
45kv, and 15kv. There are four 132kv outgoing lines which are namely called mugger, Sebeta,
Addis north or Minilik, and Kaliti. There is an industry that takes 132kv called the mugger cement
industry and the other 132kv is to another substation. A total of fifteen 15kv to the local customer
(but only ten of them are active now, five of them are idle) and one 66kv to Fitche, 45kv is taken
to Addisalem and two 45kv are ready to be distributed, but not yet.
1.5.2 Main service
The main service of refers substation is to utilize electricity for the industry like mugger fabric and
to householders for lighting purposes, for different machines such as bread machines, barbers, and
so on.
1.6 Overall Organization and Workflow
Gefersa substation is under the management of Ethiopian Electric Power (EEP). There are 42 total
workers including the guard. Out of the total workers, one of them manage this substation and 8
of them works as a technician and their job is to record the data from the control panel, line
protection panel, transformer protection panel, and feeder data within the difference of one hour.
They also make an inspection which is carried out three times a day and they do read and check
for the level of oil, winding temperature, taping position and silica gel on the transformer, and SF6
gas within the circuit breaker. They work by shifts within the eight-hour difference. The rest of the
33 workers participated in guarding and weeding the garden in the switch yard. Cleaners have been
hired through agents and they are not called the constant workers of this substation.

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CHAPTER TWO
OVERALL INTERNSHIP EXPERIENCE
2.1 Section of The Substation
Depending on the place where the equipment is installed, the substation can be sectioned into
different parts. For a voltage of less than 11kv, the equipment can be installed inside the house due
to economic considerations. Even, when the atmosphere is contaminated with impurities, it can be
erected up to 66kv. Such a type of substation is called an indoor substation. In another case, for a
voltage greater than 66kv, the equipment is not recommended to be installed in the house.
Therefore, for such high voltage, since there might be high tension between the conductor, it
requires a little more separation and should be installed outside the house. Such a type of substation
is called an outdoor substation and the place where that equipment is installed is called a switch
yard. In the following section, we will consider the equipment installed indoors and outdoors by
raising their purpose.
2.1.1 Outdoor Substation
The outdoor substation in Gefersa substation consists of the following equipment.
1. Wave Trap
In the Gefersa substation, instead of installing a communication line (due to economic
considerations), they have been using the transmission line for communication purposes from
substation to substation. This can only be achieved by filtering high-frequency communication
signals (40 – 300 Hz) from low-frequency power signals (50Hz). Wave trap had been used in
Gefersa substation for filtering purposes. But now, they are using the communication line installed
over the transmission line towers by the ethio-telecom company which is fiber optics cables.
Figure 2. 1 wave Trap

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2. Insulator
The power generated is transmitted from the generation station to the power station (substation)
and distributed to the consumers by using conductors. These conductors are hinged over towers or
poles specified for this purpose. They also should withstand mechanical stress and be stretched
between the tower or pole (the tension on the conductor should also be considered so that the
conductor should not be stretched too much i.e., a small sag is needed). This can only be done by
using an insulator. In Gefersa substations, insulators have been used for the following purpose,
 For supporting the conductor
 For stretching the conductor between the towers
 For supporting busbar
3. Conductors
The conductor is like the heart of transmitting and distributing electricity and without a conductor,
it is impossible to either transmit or distribute electricity. In Gefersa substation, they have used
two types of conductors called copper and aluminum (which is the stranded type).
4. Busbar
In electric power distribution, high current electric distribution is made by using Busbar. In Gefersa
substation there are two types of busbars namely pipe type and conductor type busbar. Depending
on their arrangement, busbars can also be section as:
 Single busbar
 Double bus bar and
 Sectionalized double bus bar or one-and-a-half system
The types of bus bar found in Gefersa substation is both double busbar and sectionalized double
busbar. Sectionalized or one-and-a-half busbar uses three circuit breakers for two circuits and this
system has been used from 230kv side. Double busbar, two busbars with two circuit breakers is
used from 132kv side with the help of bus-coupler.
5. Surge Arrestor
It is a type of protective system, used to direct high current to the ground. For example, during the
formation of a high current when the lightning hits the line, it directs the lightning to the ground
but, does not stop them or absorb them. This system has also been used for the protection of the

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bus bar at the input line, from the transformer side for transformer protection from over current
and over voltage.
Figure 2. 2 Surge Arrestor
6. Transformer
The transformer is a static device used to transform the level of voltage or current depending the
type of transformer. There are three types of transformers in Gefersa substation. These are:
 Power transformer
Which includes autotransformer, laminated core type, and earthing transformer.
Autotransformer is the type of power transformer that has one winding and the secondary side
will tap from this one winding. There are four autotransformers in Gefersa substation with
125MVA rating which change 230kv to 132kv. They are using them in parallel.
Laminated core types of transformers are the most commonly widely used in power transmission
which is used to change the level of voltage. It is different from an autotransformer due to its
winding structure. These types can have more than or equal to 2 winding. So, there are four such
transformers in Gefersa substation. All of them convert 132kv into different voltage levels such as
66, 45, and 15kv.

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[A] [B]
Figure 2. 3 [A] Auto and [B] Power Transformer
The power transformer discussed above consists of the following basic section.
 Conservator – is used to conserve the oil needed for the transformer for cooling
purposes.
Figure 2. 4 Conservator
 Silica gel - is used in breather transformers for controlling the level of moisture and
preventing it from entering the equipment.
Figure 2. 5 Silica gel

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 Buchholz relay - More severe types of faults, such as short circuits between phases or to
earth and faults in the tap changing equipment are protected by using Buchholz relay.
Figure 2. 6 Buchholz relay
 Radiator and fan – are one cooling system for the transformer by circulating oil through
its body with the help of a fan.
Figure 2. 7 Radiator and fan
 Tap changer – is needed in order to get one desired voltage. It is usually used when the
level of voltage is below or above the desired stabled voltage by changing the position of
the winding.

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Figure 2. 8 Tap changer
The following table consist some information of transformer.
Tra
nsfo
rmer
Types
of
Trans-
Former
MVA
rating
No.
of
wind
ings
Con
necti
on
output line Feeder
If exists
No. of
15kv
o/p
after
feeder
No.
of
15kv
idle
15k
v
45kv 66k
v
1 Core
type
ONAN/ONAF
40/50 & 16/20
3 Y/D yes yes no Feeder
1
5 1
2 Core
type
ONAN/ONAF
40/50 & 16/20
3 Y/D yes yes no Feeder
2
7 2
3 Core
type
ONAN 12 3 Y/Y no no yes - - -
4 Core
type
ONAN/ONAF
40/50
2 Y/D yes no no Feeder
4
3 1
Total 15 5
Table 2. 1 some information of power transformer
Earthing transformer used to provide neutral path for current to neutral for delta configuration
on the transformer. Grounding transformers most commonly incorporate a single winding

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transformer with a zigzag winding configuration but may also be created with a wye-delta isolated
winding transformer connection. Out of four transformers, three have earthing transformers.
 Instrument transformer.
Instrument transformers are typically used to operate instruments from high voltage lines or high
current circuits, safely isolating measurement and control circuitry from the high voltages or
currents. The primary winding of the transformer is connected to the high voltage or high current
circuit, and the meter or relay is connected to the secondary circuit. There are two types of
instrument transformer.
a) voltage transformer
Voltage transformers (VT), also called potential transformers (PT), are a parallel connected type
of instrument transformer, used for metering and protection in high-voltage circuits or phasor
phase shift isolation. They are designed to present negligible load to the supply being measured
and to have an accurate voltage ratio to enable accurate metering. There are three primary types of
voltage transformers (VT): electromagnetic, capacitor, and optical. The electromagnetic voltage
transformer is a wire-wound transformer. The capacitor voltage transformer uses a capacitance
potential divider and is used at higher voltages due to a lower cost than an electromagnetic VT.
An optical voltage transformer exploits the electrical properties of optical materials. Measurement
of high voltages is possible by the potential transformers. An optical voltage transformer is not
strictly a transformer, but a sensor similar to a Hall effect sensor. In Gefersa substation, there is
capacitor voltage transformer. This type of voltage transformer is used at the input line from 230kv
side, after disconnector (isolator) in order to let the circuit breaker to trip the line during faulty and
on the busbar from 132kv side on each three-phase pipe type busbar.

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Figure 2. 9 Voltage Transformer
b) current transformer
A current transformer (CT) is a series connected measurement device designed to provide a current
in its secondary coil proportional to the current flowing in its primary. Current transformers are
commonly used in metering and protective relays in the electrical power industry.
Figure 2. 10 Current Transformer
7. Disconnector (isolator)
Is used to connect or disconnect the line for maintenance purpose. This isolator is used between
the line and circuit breaker as well as between current transformer and busbar. It can be connected
or disconnected either manually or automatically.

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Figure 2. 11 Disconnector (isolator)
8. Busbar Coupler
Bus coupler is a device used to connect one end of busbar to the other in order to make load sharing
between those busbars. It can be operated manually or automatically.
Figure 2. 12 Busbar Coupler
9. Circuit breaker
Circuit breaker is a device used to trip the line automatically during fault condition in order to
make sure the safety of high-cost instrument in the substation. There are different types of circuit
breaker depending on the method of arc extinction. Those are, air blast CB, oil CB, vacuum CB
and SF6 gas CB. Gefersa substation was using air blast CB, but now they are using SF6 gas CB.
The reason they have stopped using air blast circuit breaker is it was risky since it needs time to
time inspection and requires frequent check for the air to be filled and this was tiresome.

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[A] [B]
Figure 2. 13 [A] Vertical and [B] Horizontal Circuit Breaker
2.1.2 Indoor Substation
This part includes the equipment installed inside the house. They are:
i. Control panel
The control panel which is found in Gefersa substation consist of circuit breaker and disconnector
closing and opening button. It also has a reading digital meter from which the line power, voltage
and current parameter are recorded from. It is installed for the six-input line and for the power
transformer.
ii. Protection Panel
As the name indicate, protection panel consists of different types of relays. It is also installed for
both transformer and line. The line protection panel consists of line differential relay and line
distance relay. It can be used as a reading board since it consists power, voltage and current of the
line and the substation is using them for safety purpose. The other is transformer protection panel.
This one consists transformer auxiliary relay, transformer relay and feeder relay.

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Figure 2. 14 Protection Panel
iii. Battery cell
Whenever the auxiliary transformer which supplies the control pane, protection panel, and
anything that needs supply is being out from the system, they have their own battery to as a supply.
The battery is charged from the ac supply obtained from auxiliary transformer by using rectifier.
The rectifier which is 125v/40A rating converts ac in dc to charge the battery. They use
thermometer to measure the temperature of the battery room. the following figure is captured while
we were on the internship.
[A] [B]
Figure 2. 15 [A] Battery Cell and [B] Rectifier

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iv. Digital Energy Meter
One of the responsibilities of EEU is to monthly bill from consumers for the electricity consumed.
EEP takes the payment from EEU based on the data they have from this energy meter. So, Gefersa
substation uses this meter to collects payment from utilities.
i. Auxiliary Transformer
The substation has its own transformer which supplies the instrument installed in the substation
such as control panel, protection panel and digital meter and also services like lighting and socket
outlet. These auxiliary transformer converts 15kv from transformer2 to desired 220v (phase to
neutral). It is found inside the house.
2.2 Tasks that have been executing
The tasks we have been executing are:
 Visual inspection of the substation.
The first time we have entered to the substation, the arrangement of equipment through the
substation seems too complex to understand their name and their purpose since we haven’t
done such trip to any compony like this. For some consecutive days, we have agreed so that
the workers of the substation will introduce the equipment and their purpose to us. So, for some
days, they let us to visually inspect and tell us their name with their purpose. But to grasp and
relate the concept we have learned in class with those equipment’s, this wasn’t enough. Then
we agreed to collect question by asking them a permission to walk through the substation. We
have been discussing with each other’s about what we have been seeking for. After some days,
we then took some of the workers to ask them those questions by again walking through the
substation. Since the workers works by shifts, we have been facing different workers and we
been asking them all. They did all they can to let us understand all the equipment with their
purpose.
 Going out inspection with the workers and recording data that should have to be recorded.

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By going out through the switch yard, we have been doing inspection with the workers of the
substation. The tasks in inspecting the switch yard are recording the data from transformer
(like oil level, oil temperature, high and low voltage temperature) and recording the amount of
SF6 from circuit braker.
 Recording the measurement every single hour.
This includes the data recorded from the panel which are installed inside the house. They are
the amount of voltage from Ghedo 1 and from the busbar I and II of 132KV for checking the
voltage sharing by couplers between them, the amount of MW, MVA and current from:
- all the lines including the six input lines, the outgoing lines such as Kaliti, Addis
North, Sebeta and Muger which are all 132KV. The data can be recorded from
protection or control panel for the six-input line and from protection panel for the
four 132KV lines.
- Addisalem (45KV) and Fiche(66KV) from their protection panel.
- The protection panel of the four auto-transformers and the data required to be
recorded is their tapping position
- All the 10 feeders which are feeder 1,3,5,6,8,9,11,12,13,14 (there are 15 total
feeders but 5 of them are now idle), and from each of the four core type power
transformer protection
 Resetting the relays when faults occur if the substation is told only to do so
There are several faults occurring in the transmission and distribution line. While we were in
the substation, faults were happening frequently on the distribution line such as short circuit
faults between the line and line and line and ground. When such fault exists, the relay from
protection panel shows the type of faults and fault current. For more than 66KV the substation
is not recommended to reset or try (close) the relay for current more than 5KA. This is until
LDC (load despise center) give them permission to try the relay. But for voltage less than
66KV it is possible to try (close) the relay if the line is fixed by maintainers.
2.3 Job Ethics
The job ethics in electrical work is absolutely different from the other work especially in high line
voltage. There is no tolerance we take for example, in case of faults, because we are dealing with
highly cost materials such as transformer. There is also strict punctuality. During faulty time,
unless there is a command given from LDC (load despise center) found in Gerji, in Addis Abeba

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in case of fault on high voltage line which is above 45kv or from emergency maintenance office
for 15kv line volage distributed to local consumer, it is impossible to reconnect the line which has
been out from the system due to fault having more than 5kA current. Being honesty, loyal and
peacefully communicating with workers are our gain during internship.
2.4 Challenges We Have Been Facing and How We Have Overcome Them
The monthly cost paid by the university is not actually enough. This is the most challenging factor
that influence us in our daily activity. Our activity has been very limited due to the scarcity of
budget. Another thing is we have seen only outside part of the equipment we have learned on
theory rather than looking from the inside out. This was challenging us to illustrate the working
principle and what really are exists inside that equipment.

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2.5 Single Line Diagram of Gefersa Substation
We have tried to draw the single line diagram of Gefersa substation by using ETAP software which
is shown as on the figure below.
Figure 2. 16 Single line diagram of Gefersa substation

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CHAPTER THREE
OVERALL BENEFIT GAINED
3.1 Improving Our Practical Skills
This internship played a vital (very important) role in improving our practical skills as we saw
different materials, measurement components, control components, protection components and
other equipment. We have seen how to disconnect a part of the system when one part of the system
is required for maintenance purpose and this has its own procedure. This procedure is first by
opening circuit breaker, then disconnecting disconnector and then finally grounding the line. After
maintenance, the procedure become reverse. First, ungrounding the grounded one, then
reconnecting the disconnector and finally closing the circuit breaker. Another important thing we
have improved is their circuit breaker can be operated in two different ways as locally and
automatically. Locally, the circuit breaker has also two option which are electrically and
mechanical. Electrically, there are push button through which we can open or close it, and
mechanically, there is a set of gear and we need to rotate to charge the motor (mounted inside the
circuit breaker) which let us to open and close the CB.
3.2 In Terms of New Theoretical Knowledge Acquired
The configuration of transformers is usually star from the load side and delta from the primary
side. But we had not the knowledge of where the neutral line from the star configuration goes
before, we start the internship. Later on, we recognized that earthing transformer is needed to
ground this neutral line. There is also a transformer with delta configuration from both primary
and secondary. This transformer is used in Gefersa substation to step down 132KV to 66KV which
goes to Fiche. But it has also an earthing transformer which is found Fiche.
We have confirmed that our theoretical knowledge of Gefersa substation does not work without
using DC supply for control and protection panel of the indoor substation. We have understood
that the substation uses a lead acid battery and a dry cell battery for protection of the substation
when the auxiliary transformer is suddenly turned off. So, it is possible to use battery for powering
up all the protection and control panel when there is aver all blackout. This could be extended for
lighting purpose. Another important knowledge we have acquired is, we haven’t seen and heard
of one and half system in which three circuit breaker is used to control two circuit (Gefersa
substation have used in their busbar system), wave trap which they have been using for
communication purpose for the substation to filter high frequency from low frequency in order to

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use the power transmission line for both communication and transmission of power. We have tried
our best to connect classroom learning with the real world and again refer to books to memorize
the theoretical part.
3.3 New Training We Have Taken
We have been trained on how to fetch the parameters values and how to record all the data required
to be recorded from control and protection panel. By taking this training, we have been helping
the workers of the substation.
3.4 In Improving our Inter-personal Communication Skill and Team Work
We improved our communication skills through discussion and questioning with workers of
Gefersa substation. We have gained confident of asking a question and answering and also arguing
with each other freely. By discussing problems and solutions in a polite manner with the workers
and also with our groups, we realized how important it is to improve interpersonal communication
skills. We also have been sharing ideas we have got through our journey. In identifying and
proposing a solution for the problem seen in Gefersa substations, we helped each other’s by
sectioning the tasks that should have to be done. This helped us to simplify and make our internship
journey enjoyable and also it let us to develop the spirit of being a team and believe in team-work
than individual work.
3.5 In Terms of Understanding About Work Ethics and Related Issues
The work ethics we have gained through our practice are:
 Punctuality (being on time) is very necessary
 Being honest and loyal for any fault that happened inside or outside the substation
 Recording all the data needed to be recorded on time
 Understanding someone’s thought from his or her perspective side
 Being sensible to sound to know when C.B become opened or for alarming system

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PART TWO
PROJECT CARRIED OUT
TITLE : DIGITAL METERING SYSTEM FOR TEMPERATURE
AND OIL LEVEL OF TRANSFORMER

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CHAPTER FOUR
BACKGROUND
4.1 Introduction
The power generated from generation station cannot be directly distributed to the consumers in
AC power system. So, the generated electricity should be transported a longer distance in order to
distribute it. In order to minimize the loss which could happen on the transmission line, and
withstand the consumers load, the amount of voltage generated has to be transformed to higher
level than generated. This action cannot be performed for DC power system. So, there should be
some static device that can convert the level of voltage to the desired level. This static device is
called transformer.
In high voltage line, the costs of this transformer are too high and there should be appropriate
protection system for the transformer from different faulty condition. The fault that can harm and
let parish this costly device can be internal fault, external fault or both internal and external faults.
This are, open circuit fault, overheating and winding short circuit such as earth fault, phase-to-
phase fault and interturn faults. There are different protective device used for the above faults. For
example, Buchholz device is used for all kinds of incipient faults such as insulation failure of
winding (core heating and oil level failure), earth fault relay which is used for protection against
earth fault, overcurrent relay which is used for phase-to-phase fault and over load, and differential
relay or systems which is used for protection against earth and phase faults.
In gefersa substation there are eight power transformer including autotransformer. They all have
their own protection from the fault like overheating, phase-to-phase fault, over-load fault,
insulation failure fault, inter-turn fault and earth fault. So, they do not have a problem with the
protecting transformer from different fault scenario. But, whenever the alarming system or
protection device discussed above are malfunction for some reason, any significant fault scenario
can damage the transformer and the only ways to check the safety of transformer during this time
is from the reading. Additionally, it is tiresome for the workers of the substation to go out to read
the above parameters from the transformers. So, the reading on the transformer such as oil level,
winding temperature and tap changer have to be displayed digitally so as to make the recorded
data clear and accurate for the safety of the transformer.

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This project suggests the way of making the reading of oil level, oil temperature and winding
temperature digital by using microprocessor called Arduino uno with the help of two different
sensors called ultrasonic sensor (distance sensor) and PT-100 (temperature sensor).
4.2 Statement of Problem and Proposed Solution
4.2.1 Statement of Problem
One basic problem of Gefersa substation is the reading from which they record oil level and
winding temperature is analog and is mounted outdoor on the transformer. Due to whether
condition and the meter is not displaying properly and as a result they take the reading guessing.
This can let the high-cost device, transformer, be perished. Additionally, it is tiresome for the
workers of the substation to go out to read the above parameters from the transformers.
4.2.2 Proposed Solution
Even in the absence of SCADA system, they could have read the data like oil level and temperature
of transformer digitally. The problem we have selected for our project is the problem of reading
oil level and temperature of the transformer we have discussed in section 4.2.1 and the solution we
have proposed is to mount the reading meter inside the house by making it digital. We have used
Arduino uno microcontroller as operating system and selected two different sensors, which is
ultrasonic sensor and PT100 as distance sensor (to control oil level) and temperature respectively.
There is also buzzer to alarm when the two factors are out of predefined number. We have selected
one transformer from core type transformer.
4.3 Literature Review
Enormous work has been done on protection of power transformers such as: Overload voltages,
overcurrent and external short-circuit etc. Some of those researches which had been conducted,
their setbacks, ambiguities and merits are as discussed in the subsequent paragraphs.
Works have been done to devise a highly accurate sensor that utilizes suitably compensated
Resistance Temperature Detector (RTD) for measuring temperature. Here the tip of RTD is
immersed in the transformer oil and its leads are connected to a Wheatstone bridge arrangement.
The output of the Wheatstone bridge is connected to an instrumentation amplifier; this sensor
measures the temperature by a differential-voltage measurement approach. Hence, in this paper,
an electrical resistance measurement method is proposed to measure the temperature of
transformer oil [4].

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This paper describes the use of intensity-based fiber optic sensor for continuous level measurement
of transformer oil in power transformer. Cladding removed portions of a multimode fiber act as
sensor which works on evanescent wave interaction principle. The sensing principle is based on
intensity of light which is disturbed by the change in proximity of air or oil to the sensor. The
phenomena of refraction, total internal reflection is taken into account for experimentation and
verifications. The intensity of light is detected and analyzed by using light dependent resistor
(LDR) and LabView respectively at the detecting end which provides the corresponding reading
for the level of transformer oil in which the optical fiber is immersed. A reference fiber is
introduced in parallel with the sensing fiber to eliminate the intensity variation of source light and
temperature variation of the transformer oil. The optical sensor used is well suited for real time
monitoring of transformer oil in power transformer [5].
This paper deals with the design and construction of automatic monitoring system for power
transformer parameters. An Arduino board coupled with XBEE module was programmed to enable
the monitoring of voltage, current and temperature on a typical power transformer [6].
After going through the above research papers, which are related with our project ideas, we have
decided to proceed with our project on digital metering system for temperature and oil level of
transformer. We have chosen Arduino Uno since it is cheaper and simpler to use. In the research
paper discussed above, they have used different sensors for temperature such as RTD and
intensity-based fiber optics. We have chosen RTD pt100 for temperature since it can be interfaced
simply with Arduino uno and also the most accurate sensor which is specially used when the
measured signal goes some distance. In our case, we have proposed the solution for the digital
meter inside the house so that to they can easily read the data from lcd. On another case, the first
and second review focuses on measuring temperature only but, have added a measurement of oil
level.
4.4 Objective
4.4.1 General Objective
The general objective of this project s to design digital meter that can measure the level of oil and
temperature of both winding and oil and displaying them.
1.4.2 Specific Objective
The specific objective of this projects are:

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 To design distance sensor
 To design temperature sensor
 To design power supply for Arduino, LCD and sensors.
 To locate Arduinos analog pin with sensors
 To locate Arduinos digital pin with LCD
 To change analog value obtained from those sensors to digital
4.5 Significance and Scope of The Project
As transformers are costly device, they have to be protected from harmful factors. There are
different method by which the safety of the transformer can be protected. From this method, using
different protective relays, visual inspection of the transformer and using different alarming signal
and using the recorded status of the transformer such as oil level, temperature and tap position. In
recording the status of the transformer, the quantity needed to be protected should be seen clearly
and accurately. But in Gefersa substations, the workers are challenging to record the accurate status
discussed above for the transformer. So, this project can simplify their tasks by displaying the
status of transformer digitally and also which can be mounted inside the house. The project is
tested by using simulation software called proteus with the help of Arduino uno.
CHAPTER FIVE
METHODOLOGY
5.1 Block Diagram of The Project
The main part of the project is Arduino uno microcontroller. It controls the whole circuit by giving
commands depending on the signal from sensors. There are two types of sensors namely called
ultrasonic sensor and RTD-PT100(temperature sensor). The first is used to sense the level of oil
inside the conservator and be mounted inside the conservator. It releases ultrasonic wave and the
wave is reflected back to the sensor. Based on the speed of the reflected signal, it is possible to
know the distance of that object (in this case, oil). The temperature sensor is used to sense the
temperature of winding (both low and high voltage side) and oil temperature. PT100 is immersed
in the oil to sense the temperature of oil and mounted on the winding (both high and low voltage)

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Then, all the obtained signal has been displayed on the lcd (liquid crystal display). The signal
obtained from the sensors are all in analog form. We have changed them to digital by using the
principle of changing signal from analog to digital we have learned on digital signal processing
courses. Arduino uno, the two sensors and lcd needs 5v power supply. This also has been designed.
Figure 5. 1 Block Diagram of the project
5.2 Design Procedure
Our project consists of different sensors with different working principles. The most important
things in the project are to measure all the parameters mentioned in the section 5.1 which is crucial
for the safety of transformer. To accomplish this objectives, proper mounting of the sensors is very
important and this is discussed in section 5.3.2 and 5.3.3 of this chapters. For the level of oil which
is to be measured by using ultrasonic sensors, the measuring technique is designed by us and this
is different from the technique they are using now. The level of oil is displayed in cm in our case.
Because of we could not find the oil level on which the transformer is safe or not in any standard
distance measuring parameter (they record only a number which do not have any symbol), we left
further process in the recommendation part of this projects. For the temperature of oil, H.V and
L.V windings, the sensor will measure the temperature in degree Celsius and this can be converted

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to kelvin or Fahrenheit if it is necessary. So, any number displayed on the simulation are an
assumption we have taken.
5.3 Hardware Requirement
5.3.1 Arduino Uno
Arduino Uno is a microcontroller board based on the ATmega328P (datasheet). It has 14 digital
input/output pins (of which 6 can be used as PWM outputs), 6 analog inputs, a 16 MHz ceramic
resonator (CSTCE16M0V53-R0), and a USB connection, a power jack, an ICSP header, and a
reset button. It contains everything needed to support the microcontroller; simply connect it to a
computer with a USB cable or power it with an AC-to-DC adapter or battery to get started.
The power pins are as follows:
• Vin. -The input voltage to the Arduino board when it's using an external power source (as
opposed to 5 volts from the USB connection or other regulated power source). You can
supply voltage through this pin, or, if supplying voltage via the power jack, access it
through this pin.
• 5V. -This pin outputs a regulated 5V from the regulator on the board. The board can be
supplied with power either from the DC power jack (7 - 12V), the USB connector (5V),
or the VIN pin of the board (7-12V).
• 3V3. -A 3.3-volt supply is generated by the onboard regulator. The maximum current draw
is 50 mA.
• GND.- Ground pins.
• IOREF. - This pin on the Arduino board provides the voltage reference with which the
microcontroller operates. A properly configured shield can read the IOREF pin voltage
and select the appropriate power source or enable voltage translators on the outputs to
work with the 5V or 3.3V. [7]

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Figure 5. 2 Arduino Uno
5.3.2 Ultrasonic Sensor
An ultrasonic sensor is an electronic device that measures the distance of a target object by emitting
ultrasonic sound waves, and converts the reflected sound into an electrical signal. Ultrasonic waves
travel faster than the speed of audible sound (i.e., the sound that humans can hear). Ultrasonic
sensors have two main components: the transmitter (which emits the sound using piezoelectric
crystals) and the receiver (which encounters the sound after it has travelled to and from the target).
This sensor has its own dimensions [8]. We have selected HC-SR04 Ultrasonic sensors which is
capable of measuring range of 2cm – 400cm having of operating frequency and voltage of 40KHz
and 5v DC respectively. It has length, width and thickness of 45, 20 and 15 mm respectively.
Figure 5. 3 Ultrasonic Sensor

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Proper mounting of this sensor is required to ensure best response to reflected sound wave. Steam
can change the energy in this ultrasonic wave by creating moisture on the sensor’s emitters and
receiver. But this moisture is not a problem in our case since, the transformers have its own silica
gel to let the transformer breath and clear all the moistures created in it. The mounting method we
have proposed designed on the software called PAINT 3D.
Figure 5. 4 illustration of ultrasonic sensor mounting
We have assumed the conservator has a diameter of 100cm. the sensors will be mounted at the
distance of 9.75cm from the edge of the conservator tank as seen on the figure above. Since the
thickness of this sensors is 15mm or 0.15cm the emitters of the sensor emit ultrasonic sound wave
at the distance of 10cm (since 9.75cm + 0.15cm = 5cm). Now, the sensors emitter is 90cm when
measured directly from the lower edge of the conservator. The oil level is finally:
Oil Level = 90cm – measured distance (d).
5.3.3 RTD-PT100
Resistance Temperature Detector (RTD) is a temperature sensor in which the resistance depends
on temperature. They are most commonly made up of platinum, copper, nickel alloys or various
metal oxides. But platinum is the most common material for RTD because of its reliability,
repeatability and linear temperature resistance relationship. RTD sensors made of platinum is
called PRT (platinum resistance temperature). The most common PRT sensor used is PT-100. The
number 100 represents the value of resistance at 0 degree Celsius. [9]

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Figure 5. 5 RTD PT100
We have selected PT-100 sensor for the following factor:
 It is more accurate
 It is linear and stable than any other sensor
 Its extension wire can be made of copper.
The sensor we have selected have 4 wire and this makes it more accurate.
5.3.4 Operational Amplifier
The source signal can have a respectable voltage but a source resistance that is much greater than
the load resistance. Connecting the source directly to the load would result in significant signal
attenuation. In such a case, one requires an amplifier with a high input resistance (much greater
than the source resistance) and a low output resistance (much smaller than the load resistance) but
with a modest voltage gain (or even unity gain). Such an amplifier is referred to as a buffer
amplifier or voltage follower. This circuit is commonly referred to as a voltage follower, since the
output “follows” the input [10]. There are two reasons for using op-amp (voltage follower circuit)
in our project. The first is to eliminate loading effect and the second one is to introduce high
resistance to avoid noisy currents to not lower the accuracy of the measured signal.

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Figure 5. 6 Operation Amplifier
5.3.5 LCD
A liquid crystal display or LCD draws its definition from its name itself. It is a combination of
two states of matter, the solid and the liquid. LCD uses a liquid crystal to produce a visible image.
Liquid crystal displays are super-thin technology display screens that are generally used in laptop
computer screens, TVs, cell phones, and portable video games. LCD technologies allow displays
to be much thinner when compared to cathode ray tube (CRT) technology [11]. A 20X4 LCD is
selected, since we needed to display all the measured parameters.
Figure 5. 7 LCD
5.3.6 Resistor
A resistor is a passive two-terminal electrical component that implements electrical resistance as
a circuit element. In electronic circuits, resistors are used to reduce current flow, adjust signal
levels, to divide voltages, bias active elements, and terminate transmission lines, among other uses.
High-power resistors that can dissipate many watts of electrical power as heat may be used as part
of motor controls, in power distribution systems, or as test loads for generators. Fixed resistors

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have resistances that only change slightly with temperature, time or operating voltage. Variable
resistors can be used to adjust circuit elements (such as a volume control or a lamp dimmer), or as
sensing devices for heat, light, humidity, force, or chemical activity [12].
[A] [B]
Figure 5. 8 A(Constant resistor), B (Variable resistor)
We have used two types of resistors called constant resistor and variable resistor with 1000ohm
each. The constant resistor is used to divide 5V dc across temperature sensor RTD-PT100 and
the variable resistor is used to increase or decrease the brightness of LCD and testing ultrasonic
sensor.
5.3.6 Transformer
A transformer is a type of static electrical equipment that transforms electrical energy (from
primary side windings) to magnetic energy (in transformer magnetic core) and again to the
electrical energy (on the secondary transformer side) [13].
As we are converting 220V AC into a 5V DC, first we need a step-down transformer to reduce
such high voltage. In a transformer, there are primary and secondary coils that step up or step
down the voltage according to the no of turns in the coils. Selection of proper transformer is very
important. The current rating depends upon the Current requirement of the load circuit (circuit
which will use the generate DC). The voltage rating should be more than the required voltage.
This means if we need 5V DC, the transformer should at least have a rating of 7V, because voltage
regulator IC 7805 at least needs 2V more i.e., 7V to provide a 5V voltage. In our project, we have
used a step-down transformer, which converts 220V AC to 9V AC to obtain a 5V dc supply for
Arduino Uno, ultrasonic sensor, lcd, and PT100 sensors. Hence, we have selected 9-0-9 step-
down transformers which transforms 220v to 9v AC.

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Figure 5. 9 Step-down Transformer
5.3.6 Rectifier
A rectifier is an electrical device that converts alternating current (AC), which periodically
reverses direction, to direct current (DC), which flows in only one direction. The reverse operation
is performed by the inverter. Rectification is the process of removing the negative part of the
Alternate Current (AC), hence producing the partial DC. This can be achieved by using 4 diodes.
Diodes only allow current to flow in one direction. In the first half cycle of AC diodes D2 & D3
is forward biased and D1 and D4 are reverse biased, and in the second half cycle (negative half)
Diode D1 and D4 are forward biased, and D2 and D3 are reversed biased. This Combination
converts the negative half cycle into a positive [15].
As it can be seen from the following figure, the first yellow sine wave is before AC signal is
converted to DC signal. The second wave which is blue wave is after the sine wave is rectified.
The following simulation has been done on proteus professional software.
Figure 5. 10 Rectifier

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5.3.7 Filtering Capacitor
Filtering capacitors are those that pass desired frequencies forward to other stages of the circuit
while attenuating unwanted frequencies. These capacitors should be placed near the output of the
stages of the circuit. Depending on how the capacitors are placed in the circuit, they can filter
higher or lower frequencies. A series connection will pass high frequencies to the following stage
while a parallel connection will shunt the high frequencies to the ground allowing the lower
frequencies to pass into the following stage. The output after the Rectification is not a proper DC,
it is oscillation output and has a very high ripple factor. We don't need that pulsating output, for
this we use Capacitor. Capacitor charge till the waveform goes to its peak and discharge into Load
circuit when waveform goes low. So, when output is going low, the capacitor maintains the proper
voltage supply into the Load circuit, hence creating the DC [16].
Now the value of this filter capacitor should be calculated. Here are the formulae: Let 𝑡 = 10𝑚𝑠,
we will get a wave of 100Hz frequency after converting 50Hz AC into DC, through a full wave
bridge rectifier. As the negative part of the pulse is converted into positive, one pulse will be
counted as two. So, the Time period will be 1/100= 0.01 Second= 10ms. Selection of filtering
capacitor to obtain 5V dc. V = Peak voltage – voltage given to voltage regulator IC (+2 more than
rated means 5+2=7) 9-0-9 is the RMS value of transforms so peak voltage is:
𝐶 = 𝐼 ×
𝑡
𝑉
𝐶 = 𝑐𝑎𝑝𝑎𝑐𝑖𝑡𝑎𝑛𝑐𝑒 𝑡𝑜 𝑏𝑒 𝑐𝑎𝑙𝑐𝑢𝑙𝑎𝑡𝑒𝑑
𝐼 = 𝑀𝑎𝑥 𝑜𝑢𝑡𝑝𝑢𝑡 𝑐𝑢𝑟𝑟𝑒𝑛𝑡 (𝑙𝑒𝑡’𝑠 𝑠𝑎𝑦 500𝑚𝐴)
𝑉𝑟𝑚𝑠 × 1.414 = 9 × 1.414 = 12.73 𝑉
Now 1.4v will be dropped on 2 diodes (0.7 per diode) as 2 will be forward biased for half wave.
𝑆𝑜, 12.73 – 1.4 = 11.33𝑣
When the capacitor discharges into the load circuit, it must provide 7v to 7805 IC to work so
finally V is:
𝑉 = 11.33 – 7 = 4.33𝑣
𝑆𝑜 𝑛𝑜𝑤, 𝐶 = 𝐼 ×
𝑡
𝑉
𝐶 = 500𝑚𝐴 𝑚𝑠 ∗ 10^ − 3/ 4.33 𝑢𝐹 ~ 1000𝑈𝑓

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[A] [B]
Figure 5. 11 signal A) after and B) before filtering capacitor
As we have tried to simulate the circuit with and without filtering capacitor above by using
proteus simulation software, the difference can be clearly seen that there is some noise signal
which still trig the rectified signal to not be pure DC. But after filtering capacitor is introduced to
the circuit with the value calculated in the above sections, the noise signal become omitted.
5.3.8 Voltage Regulator
A voltage regulator is a circuit that creates and maintains a fixed output voltage, irrespective of
changes to the input voltage or load conditions. Voltage regulators keep the voltages from a power
supply within a range that is compatible with the other electrical components. While voltage
regulators are most commonly used for DC/DC power conversion, some can perform AC/AC or
AC/DC power conversion as well. This article will focus on DC/DC voltage regulators [17].
A voltage regulator IC 7805 is used to provide a regulated 5v DC. Input voltage should be 2volts
more than the rated output voltage for the proper working of IC, which means at least 7v is needed,
although it can operate in the input voltage range of 7-20V. Voltage regulators have all the
circuitry inside them to provide a properly regulated DC and were chosen for our project since
they can provide the desired voltage. The signal after voltage regulators has been simulated on
proteus simulation software as shown in the following figure.

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Figure 5. 12 Voltage Regulator
5.4 Software Requirement
5.4.1 Arduino IDE
Arduino IDE is an open-source hardware and software company, project, and user community
that designs and manufactures single-board microcontrollers and microcontroller kits for building
digital devices The Arduino IDE is a free and open-source program for developing and compiling
code for the Arduino Module. It is official Arduino software that makes code compilation so
simple that even a nontechnical person may get their feet wet with the learning process. It includes
built-in functions and commands that are useful for debugging, editing, and compiling code in the
environment [18].
5.4.2 Proteus Professional
Proteus is software for microprocessor simulation, schematic capture, and printed circuit board
design. The Proteus Professional demonstration is intended for prospective customers who wish
to evaluate professional-level products. The Proteus Design Suite combines schematic capture,
SPICE circuit simulation, and PCB design to make a complete electronics design system [19].
5.4.3 Draw.io Software
Draw.io is a software that is used to draw different diagrams and flow chart simply. It can change
the drawn diagram in to image. We have used it in our system to draw block diagram and flow
chart and we have export it in to image.

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5.4.4 PAINT 3D software
There are different software that can let us draw 3 dimensional drawings such as drawing a box,
rectangle, pyramids and another different features. We have used this PAINT 3D software to
locate the ultrasonic sensors, to put the dimensions of conservator and to redraw the edge of this
conservator tank.
5.4.5 ETAP Software
It is one of energy management solution to design, operate and automate power system. ETAP is
an analytical engineering solution company specializing in the simulation, design, monitoring,
controlling, operator training, optimizing and automating power system [20]. We have used this
software to design single line diagram for Gefersa substations.

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5.5 Flow Chart
Figure 5. 13 Flow Chart

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CHAPTER SIX
RESULT AND DISCUSSION
6.1 Power Supply
In our system, ultrasonic sensor, PT100, Arduino uno and LCD are the basic component that
needs a power supply. According to the datasheet we have tried to observe for Arduino Uno, ,
ultrasonic sensor, LCD and PT100 sensors, they all need 5V. Hence, we have designed a power
supply for each of the above components and simulated it on Proteus software as shown on the
figure below.
Figure 6. 1 Power Supply
The component used to build the power supply above are discussed in section 2. From the above
figure, it can be seen that the desired 5V has been obtained finally it is measured by using DC
voltmeter as seen in the figure.
6.2 The Overall Diagram of the system
From the overall diagram shown in the figure below, there are some components that are not raised
in the rest of the project sections. The arrow like component is called power on proteus. It is used
as a supply for the components which needs supply input. In our case, they are providing 5V dc
supply to the components. We take this since the circuit become complex if we add the power
supply designed above because of space. When the project is implemented, the output of the supply
replaces this arrow-like components. The potentiometer connected to the test pin and supply of

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ultrasonic sensor is used only in this simulation. By varying this resistance, which vary the input
supply values and this can be taken as an object of which the distance is about to be measured from
the sensors. Another potentiometer connected to VEE pin of LCD is used to increase or decrease
the brightness of this LCD. It is not needed to give supply to Arduino uno on the simulation. It is
required only during implementations. The L.V and H.V written on the figure below indicates low
voltage and high voltage respectively.
Figure 6. 2 The Overall Diagram of The System
As it can be seen from the figure above, there is constant resistance of 1k ohm connected to supply
and pt100. This circuit divides the supply voltages (5V) in this constant resistor and in pt100. What
we did during measuring of temperature is, to first calculate the value of resistance of pt100 by
using voltage divider formula. After resistance is obtained, temperature can be obtained from the
formula of R = R0(1+ alpha * T) where R0 is the resistance of PT100 at 0 degree Celsius and it is
100. This has been written in the algorithm on Arduino uno.
For oil level, the ultrasonic sensor has three pins (since there is no test pin while implementation).
The ultrasonic wave travels with the speed of 340m/s. The trig pin is used as output and the echo
pin is used as an input pin. By setting the trig pin HIGH (1), the ultrasonic wave become penetrated
from the sensor and reflected back to the sensor from the oil. After delaying for 10 microseconds
(since it is enough duration for the wave to penetrated and reflected back), we then set trig pin

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LOW (0). To get the duration it takes to the wave to be penetrated and reflected back, echo pin
will measure the pulse durations and if there is no reflected wave, echo pin will be timeout after
38ms and become LOW (but if there is received reflected pulse, it will go LOW sooner than 38ms).
By using the relationship between the time and distance of ultrasonic sensor (it travels 344 m
within 1 seconds), we can measure the distance the wave travels. By dividing the obtained distance
by two (since the wave hits the oil and the return back to the sensor which means it travels twice
of the distance we needed), we have got the distance of the oil from the sensor.
6.3 Measured Values
Since the value of temperature measure should have to be taken averagely, the LCD display delays
for one second to display the value of those parameters. That’s why the word ‘wait for 1 sec’ is
displayed on lcd as shown in the figure below.
Figure 6. 3 LCD displays within 1 second difference
When the systems are initialized, the oil level is displayed immediately. But, the temperature of
H.V, L.V, and oil has to be delayed to be displayed so that the average should be displayed. So,
for the first five second, all the temperature values are zero degree Celsius.

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Figure 6. 4 The values of temperature before five second
After five second the temperature will be displayed for one second and the word ‘wait for 1 sec’
will be displayed after one second. We have confirmed as the value of temperature we have
measured are accurate from the pt100. On the simulation, the pt100 sensor has it’s own displayer
which displays the temperature digitally. The value we have obtained is equal with this value as
shown on the figure below.
Figure 6. 5 The values of temperature after five second

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CHAPTER SEVEN
CONCLUSION AND RECOMMENDATION
7.1 Conclusion
Our duration in Gefersa substation thought us a lot of new practical skills and theoretical aspects.
It helped us to develop our problem-solving technique and grasp what we have learned in the class
by reminding us the theory. We learned a lot of things beside of our academic class. We have
improved our ethical habit specially, punctuality. We have been also exchanging ideas related to
our internship program with each other and this let us to appreciate our difference and express our
perceptions through polite manner. The all benefit we have gained is because of the assistance of
the workers of the substation. They have been helping us by introducing the equipment inside the
substation and answering for our question. Generally, the duration inside Gefersa substation let us
know different strange things and it was interesting.
After some weeks, we have headed in to identifying the problem they have and we have found
some as we have tried to state in the statement of problem sections of the project part. After
selecting one problem, we then proposed a solution by discussing with each other’s. As the name
of the project indicates (digital metering system for oil level and temperature of transformer), the
purpose of this project was to display oil level and temperature digitally and mounting this inside
the house to let the workers read the parameters simply. This has been achieved by using
simulation software which means, the project does not have implementation. We hope,
implementing this project for the company will let the works of employers easy.

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7.2 Recommendation
After we have joined this substation, there were many students required the company to join and
carried out their internship program there. But the substation resists and refuse to accepts them
because of lack of enough seats for the students to let them seat and discuss. They also do not have
enough helmet which is kept for the safety purpose and we were feeling scared while walking
through the switch yard. We recommend this compony to consider the problem stated above.
In general, we have achieved our specific and general objective stated in this paper. But the project
we have done in this paper can be extended to the extent of installing the protective relays with
alarming system based on the recorded values. The oil level measured is depends on the value we
have assumed. One can limit the level on which the alarming system is activated and the circuit
breaker is commanded to be opened for the safety of the transformer.

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REFERENCE
[1]. Rohit Mehta and VK Mehta (2006). Principles of power system. (2nd
ed). (New Delhi).
(S.Chand & compony )
[2]. [online]: https://www.eep.com.et.et/en/power-transmission/ [Accessed: January 10, 2023]
[3]. Rohit Mehta and VK Mehta (2006). Principles of power system. (2nd
ed). (New Delhi).
(S.Chand & compony )
[4]. Sreekumar, Sreejith. (2019). “A highly accurate sensor for measuring the temperature of
transformer oil”
[5]. D. K. Mahanta and S. Laskar, "Oil-level measurement in power transformer using optical
sensor," 2015 International Conference on Energy, Power and Environment: Towards
Sustainable Growth (ICEPE), 2015, pp. 1-4
[6]. Amevi Acakpovi, Chiedozie Odazie, Issah Babatunde Majeed, George Eduful, Nana Yaw
Asabere. “Transformer Wireless Monitoring System Using Arduino/XBEE,” American
Journal of Electrical Power and Energy Systems. Vol. 8, No. 1, 2019, pp. 1-10.
[7]. [online] Available: https://store.arduino.cc/products/arduino-uno-rev3 [Accessed January
10, 2023]
[8]. [Online] Available: https://www.bening.com/ultrasonic-Distan. [Accessed: January 10,
2023]
[9]. [Online] Available: https://blog.beamex.com/pt100-temperature-sensor. [Accessed: Jan.
16, 2023].
[10]. Adel S Sedra; Kenneth Carless Smith. Microelectronic Circuit. (6th
ed).
[11]. [online] Available: https://www.distrelec.biz/en/dot-matrix-lcd-display-55-mm-
16display-elektronik-dem-16216-syh-py/p/17551334. [Accessed January 11, 2023].
[12]. [Online] Available: en.wikipedia.com/resistor-potentiometer/. [Accessed January 26,
2023].
[13]. [online]Available:https://www,electrical4u.com/step-down-transformers/.[Accessed
January 11, 2023].
[14]. [online].Available:https://theorycircuit.com/wp-content/uploads/2017/08/step-
downtransformer-center-tapped.jpg. [Accessed January 11, 2023].
[15]. [online]Available : https://en.wikipedia.org/wiki/Rectifier[Accessed January 11, 2023].
[16]. [online]Available:https://passive-components.eu/kemet-decoupling-and-filtering-
capacitorsguideline/. [Accessed January 11, 2023].
[17]. [online]Available : https://www.monolithicpower.com/en/voltage-regulator-types.
[Accessed January 12, 2023].
[18]. [online]Available : https://en.wikipedia.org/wiki/Arduino [Accessed January 4, 2023].
[19]. [online]Available: https://ww.shouldiremoveit.com/Proteus-7Professional37562program
[Accessed January 1, 2023].
[20]. [Online] Available : https://etap.com [Accessed January 26, 2023]

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APPENDIX I
Algorithm
1)
#include <LiquidCrystal.h>
LiquidCrystal lcd(7,6,5,4,3,2);
long v1 = A2;
long v2 = A3;
long v3 = A4;
long echopin1 = A0;
long trigpin1 = A1;
long cm1;
int count = 0;
double store1[] ={1,2,3,4,5};
double store2[]= {1,2,3,4,5};
double store3[]= {1,2,3,4,5};
double avg2 = 0,avg1 = 0, avg3 = 0;
float alpha = 0.00385;
void setup()
{pinMode(A0,INPUT);
pinMode(A1,INPUT);
pinMode(A2,INPUT);
pinMode(A3,INPUT);
pinMode(A4,INPUT);
pinMode(buzz1,OUTPUT);
pinMode(buzz2,OUTPUT);
lcd.begin(20,4);
lcd.setCursor(0,0);
lcd.print("LAMINATED CORE TYPE");
lcd.setCursor(1,1);
lcd.print("TRANSFORMER STATUS");
lcd.setCursor(4,2);
lcd.print("FOR TRAFO-IV");
2)
delay(2000);
lcd.clear();
}
void loop()
{// put your main code here, to run repeatedly:
long distance1 = sensor1() ;
double t1 = analogRead(v1);
double t2 = analogRead(v2);
double t3 = analogRead(v3);
float v1 = t1*5/1023;
float v2 = t2*5/1023;
float v3 = t3*5/1023;
float r1 = (v1/5.0)/(1-(v1/5.0))*1000;
float r2 = (v2/5.0)/(1-(v2/5.0))*1000;
float r3 = (v3/5.0)/(1-(v3/5.0))*1000;
float temp1 = ((r1/100)-1.0)/alpha;
float temp2 = ((r2/100)-1.0)/alpha;
float temp3 = ((r3/100)-1.0)/alpha;
float tolerance1 = 0.3+0.005*temp1;
float tolerance2 = 0.3+0.005*temp2;
float tolerance3 = 0.3+0.005*temp3;
temp1 = temp1-tolerance1;
temp2 = temp2-tolerance2;
temp3 = temp3-tolerance3;
lcd.setCursor(1,2);
lcd.print(" WAIT FOR 1 SEC ...");
delay(1000);
lcd.clear();
count++;

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3)
if(count>0)
{
store1[count] = temp1;
store2[count] = temp2;
store3[count] = temp3;
}
if(count==5)
{
double av1 = (store1[1] + store1[2]
+store1[3] +store1[4] +store1[5])/5;
double av2 = (store2[1] + store2[2]
+store2[3] +store2[4] +store2[5])/5;
double av3 = (store3[1] + store3[2]
+store3[3] +store3[4] +store3[5])/5;
avg1 = av1;
avg2 = av2;
avg3 = av3;
count = 0;
}
lcd.setCursor(0,0);
lcd.print("OIL.LEVEL: ");
lcd.print(distance1);
lcd.setCursor(16,0);
lcd.print("cm");
lcd.setCursor(0,1);
lcd.print("H.V.TEMP : ");
lcd.print(avg1);
lcd.setCursor(16,1);
lcd.print("'C");
lcd.setCursor(0,2);
lcd.print("L.V.TEMP : ");
lcd.print(avg2);
4)
lcd.setCursor(16,2);
lcd.print("'C");
lcd.setCursor(0,3);
lcd.print("OIL.TEMP : ");
lcd.print(avg3);
lcd.setCursor(16,3);
lcd.print("'C");
delay(1000);
lcd.clear();
}
long sensor1()
{
long duration1,cm1;
//for autotransormer
pinMode(trigpin1,OUTPUT);
pinMode(echopin1,INPUT);
digitalWrite(trigpin1,LOW);
delayMicroseconds(2);
digitalWrite(trigpin1,HIGH);
delayMicroseconds(10);
digitalWrite(trigpin1,LOW);
duration1 = pulseIn(echopin1,HIGH);
cm1 = duration1/29/2;
return cm1;
}