Gas turbine Power Station Internship Report

Internship Report
Prepared By: Asad Hussain
1
Dedicated to my loving Father

Internship Report
2
ACKNOWLEDGEMENTS
In the Name of Allah, the Most Gracious, the Most Merciful
I thank Allah Almighty for giving me the inspiration, patience, time, and strength to
finish this work. With Allah’s will and mercy I have been able to achieve all of this.
As is the case in most human productions, this report is the result of the collective
efforts of a number of important and valued people who directly or indirectly assisted and
supported me during my internship period. To these people, I owe my gratitude and
thanks.
I wish to express my deep and sincere appreciation and thankfulness to foreman
Mr. Faiz-ul-Hassan, T.I Muhammad Raffiq and all the staff of Electrical Maintenance
Block Ш for their valuable guidance, advice and cooperation.
As for as concepts of the Mechanical Engineering applied at KAPCO are
concerned, I’m very thankful to Principal Engineer Mr. Azdur Aziz Khan for his
guidance, encouragement, and support. I would always remember his ditch efforts to
make me entangled in discussions that ultimately proved to be very fruitful .It was a real
feast being with him.
.

Internship Report
3
ABSTRACT
The report is about my internship tenure which made me learn the basics of a combined
cycle power plant. The Power Plant comprises of 10 multi fuel fired gas turbines and
5 steam turbines. These turbines are divided into 3 energy Blocks with each Block
having a combination of gas and steam turbines. The Power Plant's combined cycle
technology enables KAPCO to use the waste heat from the gas turbine exhaust to
produce steam in the Heat Recovery Steam Generator, which in turn is used to run
the steam turbines thereby resulting in fuel cost efficiency and minimum wastage.
Electrical energy is generated at 11KV which is transmitted at 132KV and 220KV
by stepping up the voltage level.

Internship Report
4
Table of contents
1. Acknowledgement 2
2. Abstract 3
3. Contents 4
4. Introduction 5
5. Vision and Mission 6
6. Plant General Characteristics 7
7. Generator 9
8. Parts of Generator 11
9. Generator cooling system 14
10. Generator Protection 15
11. Power factor 16
12. Transformer 19
13. Types of Transformer 20
14. Transformer Protection 24
15. Battery rooms 26
16. Switch yard 27
17. Black Start 30
18. Neutral and Grounding 31

Internship Report
5
KAPCO
INTRODUCTION:
KAPCO is Pakistan's largest Independent Power Producer (IPP) with a name plate
capacity of 1600 MW. Kot Addu Power Plant (the "Power Plant") was built by the Pakistan
Water and Power Development Authority ("WAPDA") in five phases between 1985 and 1996 at
its present location in Kot Addu, District Muzaffargarh, Punjab. In April 1996, Kot Addu Power
Company Limited ("KAPCO") was incorporated as a public limited company under the
Companies Ordinance, 1984 with the objective of acquiring the Power Plant from WAPDA. The
principal activities of KAPCO include the ownership, operation and maintenance of the Power
Plant.
The Power Plant is a multi-fuel gas-turbine power plant with the capability of using 3
different fuels to generate electricity, namely: Natural Gas, Low Sulphur Furnace Oil and High
Speed Diesel to generate electricity. The Power Plant is also the only major plant in Pakistan
with the ability to self-start in case of a country wide blackout
On June 27, 1996, following international competitive bidding by the Privatization
Commission Government of Pakistan (the "Privatization Commission"), the management of
KAPCO was transferred to National Power (now International Power) of the United Kingdom,
which acting through its subsidiary National Power Kot Addu Limited (NPKAL), bought shares
representing a 26% stake in KAPCO. Later, NPKAL bought a further 10% shareholding in
KAPCO increasing its total shareholding to 36%.The other majority shareholder in KAPCO is
WAPDA with a present shareholding of 46%.
Following the successful completion of the offer for sale by the Privatization
Commission (on behalf of WAPDA) in February 2005, 20% of KAPCO’s shareholding is now
held by the General Public. On April 18, 2005 KAPCO was formally listed on all three Stock
Exchanges of Pakistan.

Internship Report
6
The Power Plant is situated in District Muzaffargarh, Punjab, 90 K.M. north west of
Multan on the left bank of the River Indus at a distance of 16 K.M. from Taunsa Barrage. The
area is surrounded by agricultural land on the north and west side of Kot Addu.
VISION AND MISSION
VISION STATEMENT:
“To be a leading power generation company, driven to exceed our shareholders’
expectations and meet our customer’s requirements”
MISSION STATEMENT:
 To be a responsible corporate citizen
 To maximize shareholders' return
 To provide reliable and economic power for our customer
 To excel in all aspects relating to safety, quality and environment
 To create a work environment which fosters pride, job satisfaction and
equal opportunity for career growth for the employees

Internship Report
7
Plant General Characteristics
Gas Turbines 10
HRSGs 10
Steam Turbines 5
Installed Capacity 1600MW
Max. Load Generation 1541MW
Load According to IDC Test (1996) 1345MW
Load According to ADC Test (2010) 1355MW
No. of Feeders 6 x132KV; 6 x220KV
Max. Generation in one day 35,667Mwh

Internship Report
8
KAPCO GAS TURBINE POWER STATION
KAPCO
1600MW
Block 1
Energy Block
3
SIEMENS
GERMANY
GT 1
STG 9
GT 2
FIAT
ITALY
GT 3 GT 4
STG 10
Block 2
Energy Block
2
ALSTHOM
FRANCE
GT 5,6
STG 11
GT 7,8
STG 12
Block 3
Energy Block
1
SIEMENS
GERMANY
GT 13,14
STG 15

Internship Report
9
INTRODUCTION TO ALL BLOCKS
There are total three blocks in KAPCO. And there details are given below.
Block-I:
Block-I is equipped with six turbines in total. In which four are Gas Turbine (GT1, GT2,
GT3 and GT4) and other two are Steam Turbines (STG 9, STG10). The whole system is based
on combined cycle
GT1 and GT2 are German made and are manufactured by Siemens Engineering Co. ltd. They
have overall thermal efficiency 28% and having rated capacity of 100MW. Rated speed is
3000rpm. GT3 and GT4 are Italian made and are manufactured by Fiat Engineering Co. ltd.
They have overall thermal efficiency 28% and having rated capacity of 100MW. Rated speed is
3000rpm.
Steam Turbines (STG 9, STG 10) are manufactured by ABB. As there is not any kind of
compressor which uses about 60% energy of GT, so its efficiency is increased up to 50%.
Block-II:
In block-II there is also same construction of machines but they are all made of
ALSTHOM. There rating and efficiency is same as that of block-I. All these machines are
synchronized directly with the bus bar i.e. at 220 kv to attach with bus bar.
Block-III:
Block-III is equipped with three turbines in total. In which two are Gas Turbine (GT13,
GT14) and other one is Steam Turbine (STG 15). Gas Turbines GT13, GT14 and STG 15 are

Internship Report
10
German made and are manufactured by Siemens engineering co. ltd. They have overall thermal
efficiency 45% in combine cycle mode.
LINKAGE WITH 220KV TRANSMISSION LINE
Block 1 is attached to 132KV bus bar and then with the help of autotransformers, this voltage is
converted into 220 KV to attach it with the main bus bar.
From the 132 KV bus bar, direct lines are going to different areas. Two of them are going
to KOT ADDU. The output of Block 3 is stepped up to 220KV and then transmitted.
The Generator:
Synchronous generator is used to convert mechanical energy into electrical energy.
Basic Working principle:
According to Faraday’s law of electromagnetic induction:
“If there is a relative motion between conductor and magnetic field, then an EMF will be induced
into the conductor”.
To create this relative movement, it does not matter whether the magnet is rotating and the
conductor is stationary or the conductor is moving and magnet is stationary.
The magnitude of the induced EMF is directly proportional to the No of conductors (N) and the
rate of change of magnetic flux crossing the conductors.
E = N (dΦ/dt)

Internship Report
11
Difference between AC generator and DC generator:
There is one main difference between an AC and DC generator. In DC Generator, the armature
rotates but the field system remains stationary but in AC generator, the case is reverse because
here armature remains stationary but field winding rotates.
The general thing to keep in mind in this reference is that armature is a thing, which produces
alternating magnetic field. Therefore, in DC, this magnetic field is being produced by rotor,
which is called the armature, and in AC, this remains stationary and here it is called the stator.
The stator consists of a cast iron frame, which supports the armature core having slots on its
inner periphery for housing the armature conductors. In a slip ring induction machine the rotor,
winding terminals are coming out and then they are supplied with a DC supply to produce the
stationary magnetic field, which is converted into the rotating magnetic field by rotating the rotor
by an external source, which is called the prime mover.
When the rotor rotates, the stator conductors are cut by magnetic flux, hence they have an
induced EMF produced in them. As magnetic poles are alternately N and S, they induce an EMF
and hence current starts flowing in armature conductors, which first flows in one direction and
then in the other. Hence, alternating EMF is produced in the stator conductors whose frequency
depends on the No of N and S poles moving past a conductor in one second and its direction is
given by Fleming’s right hand rule:
First finger Magnetic field
Second finger Direction of current
Thumb Motion of the conductor
Different Parts of Generator:
The two-pole generator uses directly air-cooling for the rotor winding and indirect air-cooling for
the stator winding. All types of losses (iron, friction, windage, stray and etc) are also dissipated
through air. Generally a generator consists of following parts:
 Stator
 Rotor
 Excitation system
 Carbon brushes and Slip rings

Internship Report
12
 Retaining rings
 Bearing
 Rotor grounding system
 Cooling system
Stator:
It is a stationary part of the generator. The stator has two main components:
Stator frame,Magnetic core,Stator winding,Stator End shields
Stator frame:
The frame is for to support the laminated core and winding and also for to increase the
mechanical strength of the machine. It is the heaviest part of the generator. Air ducts are
provided for the rigidity of stator frame. End shields are also bolted to this frame. For the
foundation purposes feet are provided.
Electrical connection of bars and Phase connectors:
Electrical connection between the top and bottom bars is made by brazing. One top bar strand
being brazed to one strand of associated bottom bar, so that the beginning of each strand is
connected without having any electrical contact with the remaining strands. This connection
offers the advantage that circulating current losses in the stator bars are kept small.
The phase connectors consists of flat copper sections, the cross section of which results in a low
specific current loading. The ends of each phase are attached to the circular phase connector,
which leads from winding ends to the top of the frame. The phase connectors are mounted on the
winding support, using clamping pieces and glass fabric tape.
Rotor:
It is the rotating part of the generator. It is driven by the turbine and it creates rotating magnetic
field. There are two types of rotor:
 Cylindrical type
 Salient-pole type
The cylindrical type rotor is used in turbo alternators and a having a uniform air gap. Normally it
is used in all types of thermal power stations where the rotating speed of rotor is high like 3000
rpm in PAKISTAN. For 3000 rpm, it has two poles. The field winding is accumulated in slots on
the solid rotor.

Internship Report
13
Salient pole rotors are used for low speed operation like about 167 rpm for 50 Hz. For this
arrangement, we use 36 poles of the rotor.
Rotor has the following main components:
Rotor shaft:
The rotor shaft is made of single
gorging whose ingot is made in an
electric furnace and then vacuum cast.
The rotor consists of an electrically active
portion and the two shaft ends. A forged
coupling is used to couple the rotor to the
turbine. The longitudinal slots hold the
field winding. Slot pitch is selected so that
two solid poles are displaced by 180°
electrical. In these slots field coils are
milled into shaft body and is
arranged so as to generate
magnetomotive force wave
approaching a sine wave.
Rotor teeth are provided with axial and
radial ducts enabling the cooling air to be discharged into the air gap for intensive cooling of the
end winding.
Rotor winding:
Rotor winding has also two distinct parts:
The shaft contained in shaft body.
The part outside the shaft body.
The rotor winding consists of several coils, which are inserted into the slots, and series
connected such that two coil groups form one pole. Each coil consists of several series connected
turns, each of which consists of two half turns which are
connected by brazing in the end section.
Strips of laminated glass fabric insulate the insulated
turns from each other. The edges of slots are made up of high
conductivity material and they are there to act as damper
winding. At the ends, the clots are short-circuited by
retaining rings.
Rotor fan:

Internship Report
14
The generator cooling air is circulated by two axial flow fan located at the end of the shaft. To
argument the cooling of the rotor winding, the pressure established by the fan in conjunction
with the air expelled from the discharge port along the rotor. The moving of the fan have
threaded roots for being screwed into the rotor shaft. Threaded roots fastening permits the blade
angle to the required level.
Excitation system:
The excitation system is to supply the direct current to rotor which allows the generator
to maintain a controlled voltage between its terminals when connected to the network. A voltage
regulator drives the excitation system. The excitation power for the generator is supplied by an
exciter with rotating diodes that are fitted at the end of main generator shaft.
The excitation voltage is developed by rotating Diode Bridge that supplies the rotor winding.
These rectifying diodes are given supply by an excitation transformer of which the primary
winding is supplied by the main generator. Then a three-phase thyrister bridge rectifies the
secondary winding.
Generator cooling system
The heat losses arising in the generator interior are dissipated to the secondary coolant (cooling
water) through air. Direct cooling of rotor removes hot spots and differential temperature
between the adjacent components. Indirect cooling is used for stator winding.
Air and hydrogen are two cooling media for the generator cooling. The field and armature copper
losses are evacuated by air/ hydrogen gas flowing inside the generator. The axial fans circulate
the air. In KAPCO all generators are air cooled.
Advantages of Air-cooling:
lower cost price
Easy maintenance
Short inspection
Air cooling circuit:
Cooling air is circulated in the generator by two axial-flow fans on the rotor shaft. Cold air is
drawn by fans from cooler and then divided into three parts:
Flow path 1:

Internship Report
15
It is directed into the rotor end winding and cools the rotor winding. Along this path heat of the
rotor winding is directly transferred to the cooling air.
Flow path 2:
It is directed over the stator end winding to the cold air ducts and in the stator frame
space between the generator housing and the stator core.
Flow path 3:
It is directed into the air gap via the rotor retaining rings. This path mainly cools the rotor
retaining rings, the end of the rotor body and end portion of the stator frame.
Then this flow of air is mixed up in air gap from where it goes for the cooling of the other
remaining portion of the stator core and the stator winding. The hot air is returned to the cooler
via hot air ducts re-cooling and draws again by the fans.
GENERATOR PROTECTION:
There are different types of fault can occur on to the generators so the protection of
these faults to the generators we used some protections. These are giving below.
 Negative phase sequence protection.
 Rotor earth fault protection.
 Loss of excitation.
 Reverse power protection.
 Differential protection.
 Under frequency/over frequency relay.
 Stator over current protection.
 Stator over voltage protection.

Internship Report
16
Power and Power Factor
Load Types Distribution systems are typically made up of a combination
various resistive, inductive, and capacitive loads.
Resistive Loads Resistive loads include devices such as heating elements and
incandescent lighting. In a purely resistive circuit, current
and voltage rise and fall at the same time. They are said to be
“in phase.”
True Power All the power drawn by a resistive circuit is converted to
useful
work. This is also known as true power in a resistive circuit.
True power is measured in watts (W), kilowatts (kW), or
megawatts (MW).
Inductive Loads Inductive loads include motors, transformers, and solenoids.
In a purely inductive circuit, current lags behind voltage by
90°. Current and voltage are said to be “out of phase.”
Inductive circuits, however, have some amount of resistance.
Depending on the amount of resistance and inductance, AC
current will lag somewhere between a purely resistive circuit
(0°) and a purely inductive circuit (90°).
Capacitive Loads Capacitive loads include power factor correction capacitors
and filtering capacitors. In a purely capacitive circuit, current

Internship Report
17
leads voltage by 90°. Capacitive circuits, however, have some
amount of resistance.
Reactive Loads Circuits with inductive or capacitive components are said
to be reactive. Most distribution systems have various
resistive and reactive circuits. The amount of resistance and
reactance varies, depending on the connected loads.
Reactive Power Power in an AC circuit is made up of three parts; true power,
reactive power, and apparent power. We have already
discussed true power. Reactive power is measured in volt-amps
reactive (VAR). Reactive power represents the energy
alternately stored and returned to the system by capacitors
and/or inductors.
Apparent Power Apparent power is the vector sum of true power, which
represents a purely resistive load, and reactive power,
which represents a purely reactive load. A vector diagram
can be used to show this relationship. . Larger values can be
stated in kilovolt amps (kVA) or megavolt amps (MVA).
Power Factor Power factor (PF) is the ratio of true power (PT) to apparent
power (PA), or a measurement of how much power is
consumed and how much power is returned to the
source. Power factor is equal to the cosine of the angle

Internship Report
18
theta in the above diagram. Power factor can be
calculated with the following formulas.
Solutions As we have learned, there are a number of things that can
Affect power quality. The following table provides some basic guidelines to solve these
problems. It should be remembered that the primary cause and resulting effects on the load and
system should be considered when considering solutions.
Problem Effect Solution
Sag Computer shutdown
resulting in lost data,
lamp flicker, electronic
clock reset, false alarm.
Voltage regulator, power
line conditioner, proper
wiring.
Swell Shorten equipment life
and increase failure due
to heat.
line conditioner.
Undervoltage Computer shutdown
clock reset, false alarm.
line conditioner, proper
wiring.
Overvoltage Life expectency of
motor and other
insulation resulting in
equipment failure or
fire hazard. Shorten life
of light bulbs
line conditioner.
Momentary
Power
Interruption
Computer shutdown
clock reset, false alarm,
motor circuits trip.
line conditioner, UPS
system.
Noise Erractic behavior of
electronic equipment,
incorrect data
communication
between computer
equipment and field
devices.
Line filters and
conditioners, proper
wiring and grounding.

Internship Report
19
Transients Premature equipment
failure, computer
shutdown resulting in
lost data.
Surge suppressor, line
conditioner, isolation
transformers, proper
wiring, grounding.
Harmonics Overheated neutrals,
wires, connectors,
transformers,
equipment. Data
communication errors.
Harmonic filters, K-rated
transformers, proper
wiring and grounding.
Power Factor Increased equipment
and power costs
Power factor correction
capacitors.
Transformer
transformer is a device that transfers electrical energy from one circuit to another by
magnetic coupling without requiring relative motion between its parts. It usually comprises
two or more coupled windings, and, in most cases, a core to concentrate magnetic flux. An
alternating voltage applied to one winding creates a time-varying magnetic flux in the core,
which induces a voltage in the other windings. Varying the relative number of turns between
primary and secondary windings determines the ratio of the input and output voltages, thus
transforming the voltage by stepping it up or down between circuits.It has effect on voltage,
current and phase angle.A transformer makes use of Faraday's law and the ferromagnetic
properties of an iron core to efficiently raise or lower AC voltages. It of course cannot increase
power so that if the voltage is raised the current is proportionally lowered and vice versa.
Classification:
The many uses to which transformers are put leads them to be classified in a number of
different ways by:
Power level:
It converts from a fraction of a volt-ampere (VA) to over a thousand MVA;
Voltage class:
It converts from a few volts to hundreds of kilovolts;

Internship Report
20
Cooling types:
 Air cooled
 Oil filled
 Fan cooled
 Water cooled
Application function: such as power supply, impedance matching, or circuit isolation;
End purpose: distribution, rectifier, arc furnace, amplifier output;
Winding turns ratio: step-up, step-down, isolating (near equal ratio), variable
Frequency range: power-, audio-, or radio frequency;
TRANSFORMER TYPES:
Transformers are constructed so that their characteristics match the application for which they
are intended. The differences in construction may involve the size of the windings or the
relationship between the primary and secondary windings. Transformer types are also designated
by the function the transformer serves in a circuit, such as
 Distribution Transformer
 Start-up Transformer
 Auxiliary Transformer
 Auto Transformer
 Matching Transformer
 Isolation Transformer
 Instrument potential Transformer
 isolation transformer.
 Instrument current Transformer
According to cooling media:
They are classified as,

Internship Report
21
1. Dry (Air-cooled):
These are used according to the environment temperature and heat dissipation. They are
less expensive and they require less maintenance. Its main disadvantage is that its output rating
decreases by 1amp with an increase of one ˚C temperature.
Oil type:
These transformers have following types, having oil as a cooling media.
Unit Transformer:
Unit transformers are used in many different types and applications. Unit transformers
are used oil cooled. Here unit transformers are used for very heavy duty. Block-2 Unit
transformers have ability to convert 11kv into 220kv.Unit Transformers take voltage from
auxiliary transformers and then pass it to the switchyard. Block-2 has Alsthom CGEE
transformer made of Itlay.
Start-up Transformer:
KAPCO has the ability of self-start. There are two start-up transformers. Start-up
transformer are used to step-down the voltage. Here in KAPCO they are used to step-down
132KV to 11KV and energize 11KV bus bar.
First transformer is connected with unit 1 and 2 while 2nd transformer is connected with unit 3
and 4.
All units of KAPCO are interconnected start-up transformer of unit 1and 2 can provide supply to
unit 5and 6 similarly start-up transformer of unit 3 and 4 is connected with unit 7 and 8.
Block 3 units can get supply from units 5 to 8.
Auxiliary Transformer:
They are very used to make supply of unit stable they take 11kv from unit and
transformer it to unit transformer and as well 11kv bus bar. The output voltage of unit can
different from exact 11kv, which can be 10.8kv or something so these transformers are used to
stable this value.
Auto Transformer:
Autotransformer is generally used in low power
applications where a variable voltage is required. The autotransformer is a special type of
power transformer. It consists of only one winding. By tapping or connecting at certain points
along the winding, different voltages can be obtained. Only switchyard of 132kv has four
autotransformers, which has ability to convert 132kv into 220kv they also convert, 220kv into
132kv .They are like interconnection between 132kv and 220kv.

Internship Report
22
Matching Transformer:
It is used for CT to make the voltage equal on both sides of transformer. They have small
size.
Isolation Transformer :
Isolation transformers are normally low power
transformers used to isolate noise from or to ground electronic circuits. Since a transformer
cannot pass DC voltage from primary to secondary, any DC voltage (such as noise) cannot be
passed, and the transformer acts to isolate this noise.
Instrument Potential Transformer(PT) :
The instrument potential transformer (PT) steps down voltage of a circuit to a low value
that can be effectively and safely used for operation of instruments such as ammeters, voltmeters,
watt meters, and relays used for various protective purposes. They are used for Measuring
,Control ,Protection.
Instrument Current Transformer (CT):
The instrument current transformer (CT) steps down the current of a circuit to a lower
value and is used in the same types of equipment as a potential transformer. This is done by
constructing the secondary coil consisting of many turns of wire, around the primary coil, which
contains only a few turns of wire. In this manner, measurements of high values of current can be
obtained. A current transformer should always be short-circuited when not connected to an
external load. Because the magnetic circuit of a current transformer is designed for low
magnetizing current
when under load, this large increase in magnetizing current will build up a large flux in
the magnetic circuit and cause the transformer to act as a step-up transformer, inducing
an excessively high voltage in the secondary when under no load.
Control Transformer:
Control transformers are generally used in electronic
circuits that require constant voltage or constant current with a low power or volt-amp
rating. Various filtering devices, such as capacitors, are used to
minimize the variations in the output. This results in a more constant voltage or current.
Distribution Transformer:
They are generally used in electrical power distribution and transmission systems. This
class of transformer has the highest power, or volt-ampere ratings, and the highest continuous

Internship Report
23
voltage rating. The power rating is normally determined by the type of cooling methods the
transformer may use. Some commonly used methods of cooling are by using oil or some other
heat-conducting material. Ampere rating is increased in a distribution transformer by increasing
the size of the primary and secondary windings; voltage ratings are increased by increasing the
voltage rating of the insulation used in making the transformer.
Energy losses in Transformer
An ideal transformer would have no energy losses, and would therefore be 100% efficient.
Despite the transformer being amongst the most efficient of electrical machines, with
experimental models using superconducting windings achieving efficiencies of 99.85%
energy is dissipated in the windings, core, and surrounding structures. Larger transformers are
generally more efficient, and those rated for electricity distribution usually perform better than
95%. A small transformer such as a plug-in "power brick" used for low-power consumer
electronics may be less than 85% efficient.
Losses in the transformer arise from;
Winding resistance:
Current flowing through the windings causes resistive heating of the conductors. At
higher frequencies, skin effect and proximity effect create additional winding resistance and
losses.
Hysteresis losses:
Each time the magnetic field is reversed, a small amount of energy is lost due to
hysteresis within the core. For a given core material, the loss is proportional to the frequency,
and is a function of the peak flux density to which it is subjected.
Eddy currents:
Ferromagnetic materials are also good conductors, and a solid core made from such a
material also constitutes a single short-circuited turn throughout its entire length. Eddy currents
therefore circulate within the core in a plane normal to the flux, and are responsible for resistive
heating of the core material. The eddy current loss is a complex function of the square of supply
frequency and inverse square of the material thickness.
Mechanical losses:
In addition to magnetostriction, the alternating magnetic field causes fluctuating
electromagnetic forces between the primary and secondary windings. These incite vibrations
within nearby metalwork, adding to the buzzing noise, and consuming a small amount of power.
Transformer Protections:

Internship Report
24
Protections are very important for electric devices, which protect them from destroying and make
them more safe to use. They also has importance for workers safety. Larger things has more
protections than smaller things.
For safety purpose there are two main Operations;
Alarm, Tripping
Alarm:
Alarm shows the critical situation of component. Alarm will ring when a device reaches
its critical value. It also shows indication in CCR.
Tripping:
Tripping is the next step of alarm. When machine or device don’t operate on its standard
functioning then after reasonable time breaker make the faulty component isolate and safe the
transformer.
protection for transformer
There are basically two types of protection for transformer.
Electrical
Non-Electrical
Non-Electrical Protections:
Thermal Protection
Pressure Protection
Level Protection
Thermal Protection:
Heat can be produced due to spark ,hot weather and high voltage in heavy duty
transformer. Mercury is used to ring alarm and for tripping. When transformer is heated, mercury
is moved from Pocket and operates protection.To safe the transformer we have two most
important operation alarm and tripping.
Pressure Protection:
Pressure Relief value is for body protection. In case of sparking oil is heated-up and can
damage the body of transformer . The value release the pressure that is built inside the body.

Internship Report
25
Level Protection:
Oil level decreases with the increase of temperature. On decrease of oil Alarm will ring
but oil level protection has no tripping option. As oil has basi purpose of cooling so it is very
important to maintain the oil level .
Buchholz Relay Protection:
It is used for protection of oil filled transformer having low level of oil. This relay is
installed between transformer tank and conservator. The minor faults in transformer tank below
oil level actuate Buchholz relay so as to give an alarm. The arc due to fault causes decomposition
of transformer oil. Buchholz relay is fitted in the pipe leading to the conservator. The gas is
collected in the upper part of the Buchholz relay, therefore oil level in the Buchholz relay drops
down. The float in the oil level in realy tilts down with lowering oil level. While doing so the
mercury switch attached to the float is closed and mercury switch closes the alarm circuit. The
transformer is disconnected and gas is tested.
Electrical Protections:
 High Voltage Protection
 Over-Fluxing Protection
 Earth Fault Protection
 Differential Protection
 Restricted Earth Fault Protection
1) High Voltage Protection:
High voltage can distort the insulation of transformer winding. A relay is connected in
parallel detect this fault and indication after reasonable time.
2) Over-Fluxing Protection:
Heat is produced due to over-fluxing due to increase of eddy current losses. The relay
measures the average voltage/frequency ration and ring the alarm if fault is not removed during
alarm then tripping operation will occur.
3) Earth Fault Protection:
In this case a relay which is connected with neutral point is used and safe the transformer
from over-heating.
4) Restricted Earth Fault Protection:

Internship Report
26
This is also an earth relay (only in unit transformer) it is in function when fault is near the
neutral point.
5) Differential Protection:
The differential protection operates on vector difference between two quantities. For
transformer protection, CT’S are used on both sides of transformer.The out of phase currents
flows through the relay operating coil and make the transformer safe.
THE BATTERY ROOMS
PURPOSE:
The purpose of the battery room is to provide dc supply needed for the relay action (mostly for
protection purposes).
They are also source of excitation in case of blackout thud have vital use as dc backup supply.
THE BATTERIES:
They are of the two types with respect to output voltage.
o Output voltage of 48V
o Output voltage of 220V.
They are of led acid type having sulfuric acid (H2SO4) as the electrolyte.
Ring System:
In Pakistan all Power station are interconnected through ring system NPCC is the main
head, which control all the power Stations, and tells control the process of demand and supply.
Mr. Ghulam Ishaq Khan, President of Pakistan on 20 January 1990, inaugurated the National
Power Control Centre Islamabad. This is first phase of the giant project. It envisages
implementation of the modern computerized load dispatch facilities for operating WAPDA's
power system, by setting up of one National Power Control Centre (NPCC) at Islamabad and two
Regional Control Centers at Islamabad and Jamshoro for northern and southern parts of the
network respectively. The main functions of these Power Control Centers are
National Power Control Centre system ensures supply of energy to every consumer at all times at
rated voltage, frequency and specified waveform, at lowest cost and minimum environmental
degradation. The switchgear, protection and network automation are integral parts of the modern
energy management system and national economy.The modern 3-ph, 50 Hz, AC interconnected
system has several conventional and non-conventional power plants, EHV AC and HVDC
Transmission system, Back to Back HVDC coupling stations, HV Transmission network,
substations, MV and LV Distribution systems and connected electrical loads. The energy in

Internship Report
27
electrical form is supplied to various consumers located in vast geographical area, instantly,
automatically, and safely with required quality at all times. The service continuity and high
quality of power supply have become very important.
For fulfilling the foresaid purpose, a state of the art, scientifically and technologically advanced
SUBSTATION is required. Sub-Station is the load control center of the thermal plant where
power at rated voltage, frequency and waveform is exported/imported as per requirements.
SWITCHYARD
Switchyard is a place to import/export electricity. KAPCO has two switchyard of 132 KV and
220 KV.
Switchyard of 132 KV:
 First feeder goes to INDUSTRIAL ESTATE MULTAN.
 Second feeder goes to MUZAFFARGARH-1
 Third feeder goes to GUJRAT SOUTH
 Forth feeder goes to D.I.KHAN-1
 Fifth feeder goes to D.I.KHAN-2
 Sixth feeder goes to KOT ADDU
This switchyard has single transmission scheme. This scheme is not very effective in case of
trouble because it can completely dead the line and we don’t have standby path. It contains 2 bus
bar of 132 kv and BAYs from 4 to 22. From switchyard of 132 KV 6 transmission lines go to
different part of country. BAY 18 and 20 are connected with autotransformer which convert 132
KV into 220 KV.BAY 6 and 17 are connected with startup transformer they convert 132KV into
11KV GT 1,2,3 and 4 are connected with BAY 4,5,16 and 19 respectively. While ST-9 and ST-
10 are connected with BAY 7 and 15 respectively.
Switchyard of 22o KV:
It contains two bus bar and BAYS from 1 to 14. This yard has one and half scheme of
breakers in which we have standby path to continue our transmission without any difficulty.

Internship Report
28
Total 12 feeders go out from the KAPCO six feeders are 220KV and six are 132KVA.
The detail of six feeders of 220KV is given below.
 From bay 1 feeder goes to MUZAFFAR GARH
 From bay 2 feeder goes to AES PAKGEN
 From bay 6 feeder goes to VEHARI
 From bay 7 feeder goes to NEW MULTAN 6
 From bay 13 feeder goes to NEWMULTAN 3
 From bay 14 feeder goes to NEWMULTAN 4
After step up, the 220 KV output from the generator transformer is fed to either of the two bus
bars through relays and circuit breakers and these are connected to various feeders through
various equipment’s.
Different Types of Equipment used in Switchyard:
1. BUS-BARS: -
Bus bar is a term used for main bar of conductor carrying an electric current to which
many connections may be made. These are mainly convenient means of connecting switches and
other equipment’s into various arrangements.
Every switchyard have two bus bars. Mostly are made of aluminum and all the incoming and
outgoing supplies are connected through the bus bars.
2. LIGHTENING ARRESTORS: -
These are equipment’s designed to protect insulators of power lines and electrical
installations from lightening surges by diverting the surge to earth and instantly restoring the
circuit insulation to its normal strength with respect to earth.
3. CURRENT TRANSFORMERS: -
The main purpose of current transformer is to step down the current to a level that the indicating
and monitoring instruments can read. When rated current flows through its primary winding, a
current of nearly 1 amp will appear in its secondary winding. The primary is so connected that
the current being passes through it and secondary winding is connected to an ammeter. The CT
steps down the current to the level of the ammeter.
4. POTENTIAL TRANSFORMER: -

Internship Report
29
These are used to step do the voltage to a level that the potential coils of indicating and
monitoring instruments can read. These are also used to feed the potential coils of relays. The
primary winding is connected to the voltage being measured and the secondary winding to a
voltmeter. The PT steps down the voltage to the level of the voltmeter.
5. POWER TRANSFORMER: -
These are used to step up down the voltage from one a.c voltage to another AC voltage
level at the same frequency. Unit transformer takes supply from auxiliary transformer and
transfers it to switchyard bus bar.
6. WAVE TRAP: -
Wave trap is used to prevent high frequency signals from entering other zones. NPCC is
connected with all power station through telephone line which put their signal on line and
separated from wave trap.
7. INDICATING AND METERING INSTRUMENTS: -
Ammeters, voltmeters, wattmeters, KWH meters, KVAR meters are installed in sub-station
to watch over the currents flowing in the circuit and the voltages and the power loads.
8. ISOLATORS: -
One of the cardinal measures for ensuring full safety in carrying out work on equipment
in electrical installations is to disconnect reliably the unit or the section on which the work is to
be done from all other live parts of the installation. To guard against mistakes, it is necessary that
apparatus, which makes a visible break in the circuit such as isolators, should do this.Isolators do
not have arc control devices therefore cannot be used to interrupt currents at which the arc will
be drawn across the contacts. The open arc in these is very dangerous, in that it will not only
damage the isolator or the equipment surrounding it but will also cause the flashover between the
phase in other words, it will result in short circuit in the installation i.e. why isolators are used
only for disconnecting parts after de-energizing them by opening their respective circuits by use
of their circuit breakers.
9. EARTHING SWITCHES: -
Earthing switch is used to discharge the voltage on deadlines to earth. An auxiliary
switch to provide interlock always accomplishes it.
10. CIRCUIT BREAKERS: -
Circuit breakers are mechanical devices designed to close an open contact or electrical
circuit under normal or abnormal conditions. CB is equipped with a strip coil directly attached to
relay or other means to operate in abnormal conditions such as over power etc. In here, two types

Internship Report
30
of CB are used. SF6 CB is used to control 220 KV in switchyard. Which has 6 bar pressure and
air is used to operate breaker which has a pressure of 19bar In block-3 switchyard portion
breaker are hydraulic operated and air is used for cooling.
Breaker:
It is an on load device which is used for safety purpose. It make the different electric
component separate in case of fault.
Trip Supervision:
To check the healthiness of breakers trip supervision is used which is in parallel to
breaker and in case of failure of breaker it give command the other one and operate related
breakers.
DUPLICATE BUS BAR ARRANGEMENT:
The duplicate bus bar system provides additional flexibility, continuity of supply and
permits periodic maintenance without total shut down. In the event of fault o n one bus the other
bus can be used.
While transferring the power to the reserve bus, the following steps may be performed:
1. Close tie circuit breaker, i.e. bus coupler. The two buses are now at the same potential. 2.
Close isolators on reserve bus starting from far end. 3. Open isolator’s o9n main bus starting
from far end.
Each pole of the circuit breaker comprises one or more interrupts or arc extinguishing chambers.
The interrupts are mounted on support insulators. The interrupts enclose a set of fixed and
moving contact. The moving contacts can be drawn apart by means of the operating links of the
operating mechanism. The operating mechanism of the circuit breaker gives necessary energy for
opening and closing of contacts of the circuit breaker.
GENERAL ELECTRICAL SUPPLIES IN THE PLANT
Electrical Auxiliary System
· AC Auxiliary supply system
· DC supply system
AC auxiliary supply system is used to feed all the AC auxiliaries installed in the plant. The DC
supply system, which consists of 220 V DC, 110 V DC, +/- 24 V DC, 48 V DC etc., is used for
control supplies as required for system control and protection equipment.
Black Start

Internship Report
31
Emergency Function:
KAPCO is the very valuable power station of PAKISTAN because it has the facility of
self-start. In case of complete black, it can run its self for this there is a Black start where diesel
generator produce electricity energizes the excitation bus bars of GTS.
Bus Bar:
Black start bus bar is energized my dc batteries of 220V and help the diesel generator to
start functioning
Diesel Generator:
Mostly it is not used but in case of complete blackout, it is very help to put power station
into action. It provide 11 KV and energize the common bus bar.
Neutral and Ground
Neutral:
A reference connection in a power distribution system .
Ground:
A connection to the earth or to a conductive object such as an equipment chassis.
There are two objectives to the intentional grounding of electrical equipment:
• Keep potential voltage differentials between different parts of a system at a minimum to reduce
the shock hazard.
• Keep impedance of the ground path to a minimum. The lower the impedance, the greater the
current is in the event of a fault. The greater the current, the faster an over current device will
open.

Gas turbine Power Station Internship Report

Recomendados

Recomendados

Más contenido relacionado

La actualidad más candente

La actualidad más candente (20)

Similar a Gas turbine Power Station Internship Report

Similar a Gas turbine Power Station Internship Report (20)

Último

Último (20)

Gas turbine Power Station Internship Report