1. Gujranwala Electric Power Company (GEPCO)
Internship Report
Submitted By:
Asad Munir ( University of Central Punjab)
Khateeb Sohail ( Air University, Islamabad)
M.Waqas (Superior University, Lahore)
Abbas Bashir ( Hamdard University, Karachi
Islamabad Campus)
Submitted To:
Engr.Muhammad Junaid Malik
INTERNEE AT:
P&E (PLANNING ENGINEERG)
PMU (PROJECT MANAGEMENT
UNIT)

2. • Electricity sector in Pakistan
• Wapda:
After the formation of Pakistan in 1947, electricity was
monitored by provincial agencies. In 1959 WAPDA (Water and
Power Development Authority) was established in February
1959 to unify the maintenance of infrastructure. WAPDA would
be look after all four elements of power systems i.e.
• Generation
• Transmission
• Distribution
• End consumer
WAPDA had two major wings
I. Water wing
Water wing was responsible for all the hydel generation in the
country which was mainly concerned with Mangla and
Tarbela dams.
II. Power wing
Power wing had thermal generation under its responsibility
hood. Along with thermal generation power wing would also
control transmission of electricity and the distribution to the
end user.
WAPDA was also responsible for future planning and keeping up
with the user demand.
WAPDA did its job pretty well for more almost 40 years but
with ever-growing demand and consumption of power, in late
90s Government of Pakistan decided to break down the duties
and allocate it to concerned institute. As a result different
generating and distributing companies were formed and PEPCO
was formed to look after all these newly formed companies. And
WAPDA left responsible for hydel power generation solely.
• PEPCO:
PEPCO (Pakistan Electric Power Company) is responsible for
the all the other generating units except for the hydel power,
which includes thermal and other sources and is responsible for

3. high voltage transmission of electricity throughout the county. It
would also look after most of the DISCOs and GENCOs and act
as a common link between all the DISCOs.
• GENCOs:
The list of GENCOs is given below
• Jamshoro Power Company Limited (JPCL) GENCO I
• Central Power Generation Company Limited (CPGCL)
GENCO II
• Northern Power Generation Company Limited (NPGCL)
GENCO III
• Lakhra Power Generation Company Limited (LPGCL)
GENCO IV
• NTDC:
National Transmission & Dispatch Company (NTDC) Limited
was incorporated on 6th November, 1998 and commenced
commercial operation on 24th December, 1998. It was
organized to take over all the properties, rights and assets
obligations and liabilities of 220 KV and 500KV Grid Stations
and Transmission Lines/Network owned by Pakistan Water and
Power Development Authority (WAPDA).NTDC operates and
maintains twelve 500 KV and twenty nine 220 KV Grid
Stations, 5077 km of 500 KV transmission line and 7359 km of
220 KV transmission line in Pakistan.
• DISCOs:
Distribution compnies and responsible for constructing and
maintaining 132 KV (and below) transmission lines and grid
stations and power distribution to the users. They are listed
below
• Faisalabad Electric Supply Company (FESCO)
• Gujranwala Electric Power Company (GEPCO)
• Hyderabad Electric Supply Company (HESCO)
• Sukkur Electric Power Company (SEPCO)
• Islamabad Electric Supply Company (IESCO)

4. • Lahore Electric Supply Company (LESCO)
• Multan Electric Power Company (MEPCO)
• Peshawar Electric supply Company (PESCO)
• Quetta Electric Supply Company (QESCO)
• Tribal Electric Supply Company (TESCO)
We were given an opportunity to have a training session at
GEPCO (Gujranwala electric power and Supply Company).
We were introduced by two of these departments which are:
• P&E(Planning engineering)
• PMU (Project management engineering)
PLANNING ENGINEERING (P&E):
Planning engineering refers to plan the projects in terms
of benefit to loss ratio in order to benefit both the company and the
customer. Planning engineers plans the load of customers which is of
two types i.e.:
>>Single phase load
>>Three phase load
They also used to select the type of conductor, cables depending upon
size and capacity of conductors/pvc cablesand choose feasible
distance between the poles.
PROJECT MANAGEMENT UNIT (PMU):
Project management unit deals with vender of certain components in
order to work on the project. They buy certain components from other
people. There are technical people who check the quality of the
product required by them and make sure it is useful and up to the
mark for their project. Planning engineers contact engineers in project
management unit if they require any component regarding building a
grid or a feeder or some other project. PMU includes:
>> Technical experts
>> Financial experts
Technical experts analyze the products demanded by planning
engineers and if these fulfil the constraints then engineers refer these
components to financial experts who finalize their price.

5. CONDUCTOR SYSTEM:
Conductors are used for transmission and distribution of
electricity. They are of different types. Mostly aluminum and
aluminum and steel alloy are used as conducting conductors. Parts of
conductor system are:
>> Transmission
>> Distribution
Some types of Aluminum conductors with their capacity at different
temperatures are given below:
11KV ACSR (ALL ALUMINIUM STEEL
REINFORCED) CONDUCTORS
NAME OF
CONDUCTOR
SIZE ALUMINIUM STEEL CAP CAP
60
0C
CAP
80
0C
SQUIRREL 7/083 6/083 1/083 80/120 85 120
WEASAL 7/102 6/102 1/102 110/150 110 150
RACCON 7/161 6/161 1/161 185/255 185 255
TIGER 37/093 30/093 7/093 290/380 290 380
LYNX 37/110 30/110 7/110 340/470 340 470
OSPRAY 19/176 18/176 1/176 450/660 450 660
PANTHER 37/118 30/118 7/118 430/510 430 510
DOG 6/186 7/062 250/300 200 300
RABBIT 7/132 6/132 1/132 145/205 145 205
GOPHER 7/093 6/093 1/093 95/140 95 140
High tension conductors are used for transmission of high voltage (>=
11kv) and low tension conductors are used for transmission of low
voltage level (i.e. <= 400V). The capacity of some low tension
conductors in AMP’s is given below in form of a table:
LT CONDUCTORS A.A.C (ALL ALUMINUM
CONDUCTORS) (IN AMP)
CHAFER 19/149 19/149 0 390/500 390 500
HORNET 19/128 19/128 0 310/410 310 410

6. WASP 7/173 7/173 0 230/315 230 315
EARWING 7/149 7/149 0 180/260 180 260
FLY 7/134 7/134 0 155/200 155 200
ANT 7/122 7/122 0 135/200 135 200
WEEVIL 3/144 3/144 0 95/140 95 140
GNAT 7/087 7/087 0 80/130 80 130
CABLES:
Cables are used for distribution of power to customers.
Cables used to get connections from WAPDA used as Service mains.
Cables are of different types depending upon number of coils which
are:
>> Single core cables
>> Multi core cables
Single core or multi core cables are used depending upon the quantity
of load demanded by the customer. Cables might be buried in ground
or hanged in air. Some examples of PVC cables are shown in this
table.
PVC 4/CORE CABLE
PVC 4/CORE CABLES 320 Ampere
PVC 4/CORE CABLES 175 Ampere
PVC 4/CORE CABLES 115 Ampere
PVC 4/CORE CABLES 77 Ampere
PVC 4/CORE CABLES 55 Ampere
PVC 4/CORE CABLES 32 Ampere
PVC 4/CORE CABLES 77 Ampere
PVC 4/CORE CABLES 32 Ampere
>> All aluminum, aluminum reinforced conductors
>> All aluminum steel reinforced conductors
Cables are further divided into two categories i.e.:
>> Low tension cables
>> High tension cables
R
Y
B

7. pole
SUPPLY SYSTEM:
Supply system means generation, transmission and
distribution of power at required voltage level to the customer. So,
supply system consists of:
1- Generation system
2- Transmission system
3- Distribution system
2-Generation system:
Power is generated by some external source i.e.
some other form of energy is converted to electrical energy. Source of
energy are of two types:
>>Renewable energy
>>Non-renewable energy
RENEWABLE SOURCES:
Renewable energy sources are those where fuel is
abundant i.e. fuel is not vanishing with the passage of time.
Renewable energy sources are:
>>Solar energy
>> Wind energy
NON-RENEWABLE SOURCES:
Non-Renewable energy sources are those where
fuel is vanishing with the passage of time e.eg fossil fuels. Non-
renewable energy sources are:
>>Hydal energy
>>Coil energy
>> Oil energy
2-TRANSMISSION SYSTEM:
Transmission system is of two types:

8. >> Primary transmission
>> Secondary transmission
• NEPRA:
The National Electric Power Regulatory Authority (NEPRA) is
responsible for regulating electricity in Pakistan. NEPRA has been
created to introduce transparent and judicious economic regulation,
based on sound commercial principals, to the electric power sector
of Pakistan.
NEPRA's main responsibilities are to:
• Issue Licenses for generation, transmission and distribution
of electric power.
• Establish and enforce Standards to ensure quality and
safety of operation and supply of electric power to
consumers.
• Approve investment and power acquisition programs of the
utility companies.
• Determine Tariffs for generation, transmission and
distribution of electric power
o Power System:
A power system mainly consists of 4 basic elements:
• Generation
• Transmission
• Distribution
• Load
o Generation:
Electric power generation is a process of converting some other
form of energy like thermal, mechanical, chemical and solar
energy into electrical energy. The most common ways of
generating electric power are

9. • Hydel
Electricity is produced by harnessing the potential or
kinetic energy of water. It is one of the most common and
cheapest source of electrical power. Hydel energy is not
only cheaper but also ecofriendly and does not
contaminate the environment. Micro-hydro plants are
also used for “extracting” energy from water and this
method is trending these days due to low cost.
• Thermal
Mostly thermal to electrical energy conversion is done by
burning up fossil fuels like coal, natural gas and
oil(furnace and diesel mostly). Due to this burning process
this type of generation is very dangerous to the
environment and the continuously rising oil and gas
prices makes it expensive too. These days this type of
energy conversion is demotivated.
• Renewable
Due to the ending fossil fuels renewable energy is the
new fashion. Renewable energy is cheap (although initial
cost is pretty high in some fields) environment friendly
and everlasting unlike energy from burning gases and oils.
Major resources of renewable energy are solar energy,
wind energy, tidal energy and energy from bio gas.
o Transmission system:
Electric-power transmission is the bulk transfer of electrical
energy, from generating power plants to electrical substations
located near demand centers. Most transmission lines are high-
voltage three-phase alternating current (AC), although single
phase AC is sometimes used in railway electrification systems.
High-voltage direct-current (HVDC) technology is used for
greater efficiency at very long distances (typically hundreds of
miles (kilometers)).
Electricity is transmitted at high voltages (120 kV or above) to
reduce the energy losses in long-distance transmission. Power is

10. usually transmitted through overhead power lines. Underground
power transmission has a significantly higher cost and greater
operational limitations but is sometimes used in urban areas or
sensitive locations. Typical voltage levels for transmission
systems are 132kv, 230kv, 345kv, 500kv and 765kv. These
voltages may vary from country to country.
A key limitation of electric power is that, with minor exceptions,
electrical energy cannot be stored, and therefore must be
generated as needed. A sophisticated control system is required
to ensure electric generation very closely matches the demand. If
the demand for power exceeds the supply, generation plant and
transmission equipment can shut down, which in the worst case
may lead to a major regional blackout. It is to reduce the risk of
such a failure that electric transmission networks are
interconnected into regional, national or continent wide networks
thereby providing multiple redundant alternative routes for
power to flow should such equipment failures occur. Much
analysis is done by transmission companies to determine the
maximum reliable capacity of each line (ordinarily less than its
physical or thermal limit) to ensure spare capacity is available
should there be any such failure in another part of the network.
o HVDC:
High-voltage direct current (HVDC) is used to transmit large
amounts of power over long distances or for interconnections
between asynchronous grids. When electrical energy is to be
transmitted over very long distances, the power lost in AC
transmission becomes appreciable and it is less expensive to use
direct current instead of alternating current. For a very long
transmission line, these lower losses (and reduced construction
cost of a DC line) can offset the additional cost of the required
converter stations at each end.
HVDC links can be used to control problems in the grid with
AC electricity flow. The power transmitted by an AC line
increases as the phase angle between source end voltage and
destination ends increases, but too large a phase angle will
allow the systems at either end of the line to fall out of step.
Since the power flow in a DC link is controlled independently
of the phases of the AC networks at either end of the link, this
phase angle limit does not exist, and a DC link is always able to
transfer its full rated power. A DC link therefore stabilizes the
AC grid at either end, since power flow and phase angle can
then be controlled independently

11. o Distribution system:
An electric power distribution system is the final stage in the
delivery of electric power; it carries electricity from the
transmission system to individual consumers. Distribution
substations connect to the transmission system and lower the
transmission voltage to medium voltage ranging between 2 kV
and 35 kV with the use of transformers. Primary distribution
lines carry this medium voltage power to distribution
transformers located near the customer's premises. Distribution
transformers again lower the voltage to the utilization voltage of
appliances and typically feed several customers through
secondary distribution lines at this voltage. Commercial and
residential customers are connected to the secondary distribution
lines through service drops. Customers demanding a much
higher high load may be connected directly at the primary
distribution level or the sub-transmission level.
There are three basic types of distribution system designs:
1. Radial
2. Loop/Ring
3. Network
We can use combinations of these three systems, and this is
frequently done. More detailed types are:
• Radial System
• Closed Loop System
• Open Loop System
• Double Supply System
• Grid Form of HV Distribution system
• Improved Radial System
But we will limit our discussion to basic distribution systems
only.
o RADIAL SYSTEM:
All the Sections/ Branches of a Feeder are Fed from a Single
Source in a Fixed Direction. No Alternate arrangement for

12. energizing the Affected Section through by-passing the Faulty
Section.
A representative schematic of a radial distribution system is
shown in figure. Note that the independent feeders branch out to
several distribution centers without intermediate connections
between feeders. The most frequently used system is the radial
distribution system because it is the simplest and least
expensive system to build. Operation and expansion are simple.
It is not as reliable as most systems unless quality components
are used. The fault or loss of a cable, primary supply, or
transformer will result in an outage on all loads served by the
feeder. Furthermore, electrical service is interrupted when any
piece of service equipment mustbe de-energized to perform
routine maintenance and service. Service on this type of
feeder can be improved by installing automatic circuit breakers
that will reclose the service at predetermined intervals. If the
fault continues after a predetermined number of closures, the
breaker will lock out until the fault is cleared and service is
restored by hand reset.
Total load current through main section increases IR and IR as
compared with system which facilitates load current
distribution in two or more parallel paths.

13. In the absence of any emergency load, thinner conductors are
used. This contributes to increase Voltage Drop and Line
Losses.
o LOOP/RING DISTRIBUTION SYSTEM:
The loop, or ring, system of distribution starts at the substation
and is connected to or encircles an area serving one or more
distribution transformers or load centers. The conductor of the
system returns to the same substation.
The loop system (shown in the figure) is more expensive to
build than the radial type, but it is more reliable. It may be
justified in an area where continuity of service is of
considerable importance, for example, a medical center.
In the loop system, circuit breakers sectionalize the loop on
both sides of each distribution transformer connected to the
loop. The two primary feeder breakers and the sectionalizing
breakers associated with the loop feeder are ordinarily
controlled by pilot wire relaying or directional overcurrent
relays. Pilot wire relaying is used when there are too many
secondary substations to obtain selective timing with directional
overcurrent relays.
A fault in the primary loop is cleared by the breakers in
the loop nearest the fault, and power is supplied the other way
around the loop without interruption to most of the connected
loads. Because the load points can be supplied from two or
more directions, it is possible to remove any section of the loop

14. from service for maintenance without causing an outage at other
load points. If a fault occurs in a section adjacent to the
distribution substation, the entire load may have to be fed from
one side of the loop until repairs are made. Sufficient conductor
capacity must be provided in the loop to permit operation
without excessive voltage drop or overheating of the feeder
when either side of the loop is out of service. If a faultoccurs in
the distribution transformer, it is cleared by the breaker in the
primary leads; and the loop remains intact.
o NETWORK DISTRIBUTION SYSTEM:
The network and radial systems differ with respect to the
transformer secondaries. In a network system (see figure)
transformer secondaries are paralleled; in a radial system, they
are not.
The network is the most flexible type of primary system; it
provides the best service reliability to the distribution
transformers or load center, particularly when the system is
supplied from two or more distribution substations. Power
can flow from any substation to any distribution transformer or
load center in the network system. The network system is more
flexible with regard to load growth than the radial or loop
system and is adaptable to any rate of load growth. Service
readily can be extended to additional points of usage with
relatively small amounts of new construction. The network
system, however, requires large quantities of equipment and
extensive relaying; therefore, it is more expensive than the
radial system. From the standpoint of economy, the network

15. system is suitable only in heavy-load-density areas where the
load center units range from 1,000 to 4,000 kilo-volt-
amperes (kVA).
The transformers of a secondary network distribution
system are connected in parallel through a special type of
circuit breaker, called a network protector, to a secondary
bus. Radial secondary feeders are tapped from the secondary
bus to supply loads. A more complex network is a system in
which the low- voltage circuits are interconnected in the form
of a grid or mesh. If a primary feeder fails or a fault occurs on a
primary feeder or distribution transformer, the other
transformers start to feed back through the network
protector on the faulted circuit. This reverse power causes the
network protector to open and disconnect the faulty supply
circuit from the secondary bus. The network protector operates
so fast that there is minimal exposure of secondary equipment
to the associated voltage drop.