Nuclear Power Corporation of India Ltd
(A Govt. of India Enterprise)
KUDANKULAM NUCLEAR POWER PROJECT(KKNPP)
In-Plant Training Report
2023
(Duration:28/06/2023 TO 14/06/2023)
Name of Institute
ROHINI COLLEGE OF
ENGINEERING AND
TECHNOLOGY
Pursuing Degree with Discipline And Academic
year
Signature
B.E Electrical and Electronics Engineering
2020-2024
Guided by:
Submitted By:
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ACKNOWLEDGEMENT
We extend our supreme gratitude to Kudankulam Nuclear Power Project for
providing such kind of opportunity for students to broaden their perception on
nuclear power plant and energy generation looks like as well organizing the
whole in-plant training program and its effort to achieve its desired goals.
Iam very much delighted on getting industrial training at Kudankulam Nuclear
Power Project. The In-plant training proved very much valuable to us and it
added worth in our engineering knowledge.
I would also like to express my special thanks to Shri P.Vetrivelan sir and Shri
G.Jayachandra sir for giving us a chanceto spend our practice under their
valuable guidance during my training.
I also extend grateful thanks to the entire electrical maintenance group
engineers,supervisors & tradesmen's for their support and help during my Visit.
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1.Introduction:
Kudankulam Nuclear Power Plant is the largest nuclear power station in
India,situated in Kudankulam in the Tirunelveli district of the southern Indian
state of TamilNadu. KudankulamNuclear Power Project (KKNPP) envisages
Russian VVER(Voda Voda Energy Reactor). The VVER reactors belong to the
family of Pressurized Water Reactor (PWR). This type of reactor uses light
water as coolant and moderator and enriched uranium (about 4.4% U max.) as
fuel.
Reactor is intended for conversion of nuclear fuel energy by fission reaction
into heat and its transfer to the primary circuit coolant of the nuclear power
plant. The primary circuit coolant transfers its energy to secondary water in
steam generator.
The VVER-1000 reactor plant consists of four circulating loops each containing
a horizontal steam generator, a main circulating pump and connecting pipe lines
with interconnection to other systems. The steam generated in four steam
generator is fed to a common header and to turbine also. The simplified sketch
of VVER-1000 is shown in figure-1.
Figure-1
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KKNPP turbine consists of one high pressure cylinder (five stage dual flow
type) and three low pressure cylinders (five stage dual flow type). The turbine is
coupled to the generator unit for converting turbine's mechanical power into
electrical power.
For the generation of electrical power from generator, lots of station auxiliaries
are required be run. The arrangements of power supply to station auxiliaries are
called station auxiliary power supply system.
The generated power from station generator is fed to the grid. The arrangements
for evacuating the generated electrical power to the grid is called power output
system. This project is to study the power output system and station auxiliary
power supply systems.
SPECIAL FEATURES OF KUDANKULAM NUCLEAR REACTOR:
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Ithasacapacity ofgenerating 2X 100OMWelectric power.
ItcomesunderGeneration-3 category
Technology of unbounded pre-stressing cable systemis used.
Theinnercontainmentwall isabletowithstand apressureofabout4ks/cm2.
Itcanwithstand earthquake rangesbelow 7 inRichterscale.
12 heat exchangers for passive decay heat removal for an unlimited
period of heatremoval.
8 additional hydraulic accumulatorsfor passivereactorcorecooling.
New passive fast boron injection system to transfer the reactor in a subcritical state.
Passive heat removal system to provide cooling for the removal of decay
heat using atmospheric air.
Higher redundancy for safety system.
Double containment.
Additional shut down systems like quick boron and emergency boron
injection systems to ensure absolute safety for shut down of the reactor,
when needed.
Core catcher to provide safety in the unlikely event of fuel melt-down
Passive hydrogen re-combiners which do not need any power supply to
absorb any hydrogen liberated inside the containment.
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Construction
Construction began on 31 March 2002, with Nuclear Power Corporation of
India Ltd (NPCIL) predicting that the first unit would be operational in March
2007, instead of the original target of December 2007.
A small port became operational in Kudankulam on 14 January 2004. This port
was established to receive barges carrying over-sized light water
reactor equipment from ships anchored at a distance of 1.5 kilometres (0.93 mi).
Until 2004, materials had to be brought in via road from the port
of Thoothukudi, risking damage during transportation. In 2008, negotiations on
building four additional reactors at the site began. Though the capacity of these
reactors had not been declared, it was expected that the capacity of each reactor
will be 1,200 MW (1.2 GW). The new reactors would bring the total capacity of
the power plant to 6,800 MW (6.8 GW).
The ground-breaking ceremony for construction of third and fourth units was
performed on 17 February 2016 and AERB authorised the first pour of concrete
on 19 June 2017. Construction of the third and fourth units started on 29 June
2017. AERB granted excavation permit for Unit 5 and 6 in 14 November 2018
and concerete pour begun in 2020. Construction of units 5 and 6 commenced on
29 June 2021. Unit 5 is expected to be ready for commissioning in December
2026, while unit 6 is expected to be ready by September 2027.
2.KKNPP POWER OUTPUT SYSTEM:
2.1 Introduction:
The power output and evacuation system comprises the Generator, 24 kV
Isolated phase bus ducts, Generator Circuit Breaker, Generator
transformers, 400 kV, 220 kV GIS and bus ducts, interconnecting
autotransformers and associated equipments .
Following are components of the Power Output System for KK NPP:
a) 1000 MWe generator
b) Generator Circuit breaker SF6
c) Generator transformer
d) 400 kV switchyard
e) 220kV switchyard
f) Interconnecting transformers (between 220kV and 400kV)
g) Transmission lines for power evacuation (Six numbers of 400 kV
transmission lines, Three numbers of 220 kV transmission lines).
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The electrical power, generated at 24 kV, three phase, 50 Hz by the
turbogenerator, is stepped up through the 24/400 kV generator transformer and
is evacuated through four numbers of 400 kV transmission lines. As a reserve
source of power supply, Kudankulam NPP is connected to two 220 kV
substations through two numbers of 220 kV transmission lines. 400 kV and 220
kV buses at Kudankulam NPP are interconnected through two numbers of
three-phase interconnecting autotransformers of315MVAeach. Normally the
generated power is evacuated through 400 kV transmission lines. However,
since 400 kV and 220 kV systems are interconnected, power can flow through
220 kV lines depending on generation / load scenario.
The generator for the KKNPP is rated with a power capacity of 1000 Mw,
three-phase, frequency 50 Hz, pf. 0.9 at the voltage of 24 kV. The generator
transformer capacity is determined based on the necessity to evacuate the full
power output of the generator. Due to the limitations imposed by the size,
weight and transportation problems, three single phase 24/400 kV generator
transformers are planned with a rating of 417 MVA each. One single-phase
unit of generator transformer is also envisaged as a spare for both the units of
NPP and installed without connecting into the system.
Indoor SF6 gas insulated (GIS) 400KV switchgear and 220 KV switchgear has
been adopted. The generator is connected to generator transformers through the
isolated phase bus duct through a 24 kV, 30kA generator circuit breaker.
The main advantages of having a GIS are as follows:
a) Small space requirements - as low as 10%ofthat required for a Air
insulated Switchyard.
b) The effects of saline/polluted, humid environment on the performance
and maintenance is taken care of as all the live parts are enclosed in SF6
gas and is not directly exposed to air.
c) The GIS comprises modular design and therefore easier erection and
standardized practices
d) Extension, if and when required can be done without shutting down the
entire switchyard as in the case of a Air insulated switchyard.
e) Low maintenance when compared with Air insulated switchyards.
Except for the high initial cost which is around 200% (approximately) of
air insulated switchyard, which again is offset in the longer run with
lower outages, and down time, GIS is quite advantageous and most of
the present power stations are slowly going in for it.
SF6 serves as insulator and as arc-extinguishing medium in the breakers. SF6 is
known to be one of the best insulating mediums. SF6 gas is, odourless, non
toxic, non inflammable, twice strong dielectrically and 5 times heavier than air
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The provision of GCB allows the scheduled start-up and shutdown of the power
unit from the 400 kV system, through Generator transformer and Unit auxiliary
transformer with GCB in open position.
On the 220 kV side, two groups of2 x 63 MVA reserve auxiliary transformers
(one group for each unit), 63 MVA common station auxiliary transformer, three
220 kV transmission lines and two 400/220 kV interconnecting auto
transformers are planned.
Safety is at the core of Kudankulam nuclear reactors
Figure-2
Since the sea water level rises due to wave run-up, storm surge, tide
variation and tsunami, the plant has to be protected from these natural
events. KKNPP is well protected from a possible rise in sea level by locating
the entire plant site at a higher elevation. The safe grade elevation of
KKNPP site has been kept at 7.5 metres above the MSL (mean sea level)
and a shore protection bund has been constructed all along the shore to a
height of + 8.0 metres to the MSL. All the buildings along with their
respective equipment are located at higher elevations as shown in Figure 1
(at left). In addition to having a higher grade elevation, all the safety-related
buildings are closed with double gasket leak tight doors.
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KKNPP is located in Indian Seismic Zone II, which is the least seismic
potential region of our country. However, for designing of the plant, detailed
studies were conducted to conservatively estimate the extent of ground
motion applicable to the specific site with reference to seismotectonic and
geological conditions around it so that the nuclear plant was designed for a
level earthquake which has a very low probability of being exceeded. The
plant's seismic sensors safely shut down the reactor in case the seismicity
exceeds the preset value. Thus, despite KKNPP being located in a very low
seismic zone, it is adequately designed to withstand the seismic events.
The two reactors that have been built at Kudankulam are advanced models
of the Russian VVER-1000 MW Pressurised Water Reactor which is a
leading type of reactor worldwide. VVER is a Russian nomenclature for
water-cooled and water-moderated reactors. Each reactor at Kudankulam
will generate 1000 MW. It uses low-enriched uranium fuel in oxide matrix,
housed in sealed zirconium-niobium alloy tubes. KKNPP VVER 1000
adopts the basic Russian design with enhanced safety features to make it in
line with IAEA GEN III reactors. Further, certain additional safety features
were incorporated like passive heat removal system and core catcher, taking
it to GEN III+ category.
The following safety functions are performed in any operational state of the
reactor:
Control of the Reactivity (control of fission chain reaction), removal of heat
from the fuel core and confinement of radioactivity.
For the control of reactivity, control rods are provided, which will ensure the
shutdown of the reactor, thereby terminating the chain reaction, whenever
the action is called for. The control rods are designed to fall by gravity to
shut down the reactor.
The salient safety features of KKNPP
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- Passive heat removal system to provide cooling for the removal of decay
heat using atmospheric air.
- Higher redundancy for safety system.
- Double containment.
- Additional shut down systems like quick boron and emergency boron
injection systems to ensure absolute safety for shut down of the reactor,
when needed.
- Core catcher to provide safety in the unlikely event of fuel melt-down
- Passive hydrogen re-combiners which do not need any power supply to
absorb any hydrogen liberated inside the containment.
The above systems have been developed based on extensive R & D and
simulated testing by the Russian design institutes. The functional
performance of these systems have been established during the
commissioning stage.
A large number of process systems are provided for the purpose of heat
removal from the reactor fuel core. In addition, to remove the decay heat
after the shut down, a series of safety systems are provided which are backed
by the diesel electricity generator sets. The safety systems are provided in
four trains, each train containing a set of safety systems, both active and
passive systems. Each set of safety trains is provided with a dedicated diesel
generator set of 6 MW. The passive heat removal system provides the core
cooling in case of rare occasion of non availability all the diesel generators.
This system uses the simple atmospheric air to take away the heat from the
reactor through steam generators by using the natural principle of
convection. One safety train is sufficient to completely ensure heat removal
from the fuel core. However, three additional safety trains, i.e., additional
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300% systems are provided making the KKNPP reactors among the safest
reactors.
The confinement of radioactivity is achieved by the principle of defence in
depth. This concept provides a set of barriers, one after the other, so as to
contain radioactivity within the reactor building. This concept is illustrated
in Figure 2 (at right).
The reactor building has double containment structure. The primary or inner
containment is a pre-stressed concrete structure, with the thickness of 1.2
metres. This inner containment is provided with leak-tight inner steel liner.
The outer containment known as secondary containment is a reinforced
concrete structure with thickness of 0.6 metres. The multiple barriers, as
shown in Figure-2, including the containment structure, ensure that no
radioactivity reaches the public domain. The double containment structures
also protect the plant from external hazards like hurricane, shock waves, air
attacks, seismic impact, floods, etc.
In addition, there are two important systems which provide safety function,
viz., hydrogen re-combiners and a core catcher. The hydrogen re-combiners
are passive devices. Hydrogen, if generated during any accident conditions,
is recombined in the passive hydrogen re-combiners to convert it to water.
This prevents any hydrogen explosion within the containment as happened
at Fukushima in Japan in March 2011. There are 154 hydrogen re-combiners
at various locations within the containment.
The core catcher is a special feature of KKNPP. It is a huge vessel weighing
101 tonnes. In case of an extreme hypothetical case, wherein an event causes
damage to the fuel core resulting in partial core damage, the core catcher
will collect the molten core, cool it and maintain it in sub-critical state.
At Kudankulam, a fish protection facility is provided in the intake of sea
water. This facility assists juvenile fish, which drift along with the flow of
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cooling sea water, from not getting trapped in the machinery. The fish are
helped in getting back to the sea and the fish population is thus conserved.
The product water and domestic water requirement of KKNPP are fully met
by a desalination plant at the KKNPP site, based on Mechanical Vapour
Compression technology.
Thus it can be safely concluded that the reactors at KKNPP are the built with
the state of the art technology, with the best safety features that will ensure
safe operation of the reactors, without any impact to the environment and the
public.
Allocation of power
Government of India announced the power allocation from the two units of the
reactor on 29 August 2013.
Beneficiary
Power (MW)
Tamil Nadu
925 MW
Karnataka
442 MW
Kerala
266 MW
Puducherry
67 MW
unallotted
300 MW
Total
2,000 MW
As of 1st December 2021, the government is considering to increase its
capability to 6000 MW, on completion of KKNPP-3 & 4 (2 X 1000 MW) and
KKNPP-5 & 6 (2 X 1000 MW) which are presently under construction.
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BASIC REQUIRMENT TO GET INTO NPP
 Industrial safety training.
 Emergency preparing training.
 First aid training.
INDUSTRIAL SAFETY
(Mandatory safety requirements inside plant)
 Safety shoes.
 Safety helmet.
 Job specification ppe (Personal Protective Equipment).
WORK PERMITS
Types of safety permits at KKNPP
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ISP – Industrial Safety Permit
CWP – Cutting Welding permit
RWP – Radiation Work Permit
DR – Deficiency Report
CSP – Confined Space Permit
TYPES OF HEIGHT SAFETY
 Scafolding Safety
 Ladder Safety
 Fall Ceiling Safety
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EMERGENCY PREPARING TRAINING
At KKNPP in a year the following announcements will be given to
the employees to test their attention level and to train them for
emergency situations.
 1 Plant emergency exercise
 2 Site emergency exercise
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EMERGENCY LEVELS ARE CLASSIFIED INTO THREE
TYPES AT KKNPP
 Plant
 On site
 Off site
Each of the emergency level will be indicated with different sounds
with variable announcements.
RESPONSIBILITIES DURING EMERGENCY PERIOD
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To inform others.
Proceed to assembly areas nearby.
In site 9 assembly areas are there.
In plant 6 assembly areas are there.
Assembly areas are indicated with signed boards.
Don’t get panic and spread rumours.
Shelter areas to evacuate from assembly areas in-case it is
needed.
 Declaration siren: 5sec on , 5sec off for 2min duration.
 Termination siren: Continuous siren for 2 min.
SAFETY MEASURES:
 Fire emergency
 Radiation emergency
CLASSES OF FIRES
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Class A – Normal fire
Class B – Liquid fire
Class C – Gas fire
Class D – Metal fire
Class E – Mineral fire
TECHNIQUES TO FIRE EXTINGUISH
 Starvation
 Smothering Blanket
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 Cooling
EMU
(ELECTRICAL MAINTENANCE UNIT)
Electrical maintenance unit is a group of engineers covers all aspects
of testing, monitoring, fixing,and replacing elements of an electrical
system. Usually performed by a licenced professional with a complete
knowledge of the National Electric Code and local regulations,
electrical maintenance covers areas as diverse as:
o Digital communication
o Electrical machines
o Generators
o Hydraulics
o Lighting system
o Surge protection
o Transformers
Electrical maintenance unit is subdivided into 7 groups. Each group
carries controlling of electrical systems of KKNPP power output
sytem.
GROUP -1
6KV SWITCH GEAR
Introduction:
The 6kV switchgears are intended for reception and distribution ofa
three-phase AC, 50Hz power to NPP auxiliaries of loads more than
200kW.
Description of the system:
The switchgear cabinets of all types have a rigid construction, in which
the CBs, bus bars, voltage transformers, and current transformers are
housed. In the upper part of the switchgear cabinets, the devices of a relay
protection, equipment of control, measurement and signal systems,
terminal blocks and secondary connections circuits are installed.
The switchgear cabinets are provided with drawers, in which the circuit
breakers, voltage transformers are located. The construction of the
switchgear cabinets and carriage-type elements provides an opportunity
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to put in service and control (test) positions and also their fully withdrawn
position from the cabinet for inspection and repair.
The cabinets with SF6 circuit breakers have a high switching and high
mechanical operation reliability.
SWITCH GEAR:
Switch gear refers to a centralized collection of circuit breakers, fuses
and switches (protection devices) that functions to protect, control and
isolate electrical equipment.
Figure – 3
CIRCUIT BREAKER:
A circuit breaker is an electrical switch designed to protect an
electrical circuit from damage caused by overcurrent/overload or
short circuit. Its basic function is to interrupt current flow after
protective relays detect a fault.
TYPES:
o Air circuit breaker
o Vacuum circuit breaker
o Sf6 circuit breaker(sulphur hexafluoride circuit breaker)
In 6kv switch gear sf6 circuit breaker is used.
WHY SF6 CB IS USED?
SF6 is sulphur hexafluoride circuit breaker in which sulphur
hexafluoride is used as the arc extinguishing medium instead of oil,
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air or vacuum. The sf6 gas attracts free electrons. As the circuit
contacts are opened, the gas flows through the chamber striking the
arc.
Figure – 4
SPECIFICATIONS OF CIRCUIT BREAKER
Circuit breaker
Rated continuous current for Incomers, A:
Rated continuous current for Feeders, A:
Rated short-circuit breaking current, kA(rms)
Duty cycle
CB opening time, ms
CB closing time, ms
Type of operating mechanism
Type SF6
3150/1250/2500
630
40
O-3sec-CO -3min
70
72
Motor operated springcharged
Rated control power supply voltage,
Number of trip coils
Emergency mechanical trip
V220 DC
Two
Provided
RELAY:
Relay is an electrically operated switch. It is the device that opens or
close the contacts to cause the operation of the other electric control.
Relays control one electrical circuit by opening and closing in another
circuit.
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Figure – 5
Bus Bar
Type of switchgear
Rated voltage, kV Metal clad, Draw out type
Power frequency withstand voltage, kV
Peak impulse withstand voltage, kVp
Rated continuous current of bus bars, A
Rated short circuit withstand current for 1s, kA
Material of the bus bars
Maximum allowable temperature of the bus bars, deg.
Control power supply
Protection class
o
o
o
o
o
o
o
Metal clad, Draw out type
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25
60
3150/1600
40
Copper
C 95
220 V DC
IP 41
6kV switchgears are provided with:
Cells with drawout type circuit breakers of different feeders.
Cells with drawout trolley of voltage transformer.
Cells with drawout trolley of tie disconnectors.
Bus bar chamber.
Relay and secondary connection cabinet.
Cabling of loads.
Important features
 6KV circuit breaker is provided with local Closing/Tripping
mechanical push buttons (red color push button for closing and
black color push button for tripping).
 6KV circuit breaker is provided with foot paddle, electromagnetic
lock& handle for in & out movement inside the switchgear
cabinet.
 The switchgear cabinet is provided with electromagnetic locks and
drive blocking casing for earthing switch operations.
 The switchgear is provided with DC ground fault indication lamp
in VT cubicle.
 6KV circuit breakers are provided with manual spring charging
facility and indication for status of spring (charged or uncharged).
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 6KV circuit breakers are provided with operating counters to
indicate the cumulative number of operations
 6KV switchgears are provided with limit switches on draw-out
units (carriages) with Test, Service and With-drawn positions.
 6KV switchgears are provided with photo-thyristers for are
protection sensing in bus bar compartments.
 6KV switchgears are provided with limit switch on the top of
cabinet with flap type cover for arc protection of circuit breaker
compartment.
 Trip of circuit breaker automatically on electrical protection if SF6
pressure inside circuit breaker chamber reduced down to the pre-set
value.
 The protection shutters ensure the draw-out element section secure
functioning. When rolling the draw-out element out from the
service position into the repair one the shutters automatically close
and disable any access to the fixed powered terminals.
 For racking in or racking out of circuit breaker, a racking in/
racking out handle is used.
Important interlocks
In order to prevent malfunctions of the electrical circuits by the operating
personnel, the following provisions are provided in the 6KV switchgear:
 rolling-in ofthe carriage into a service position with closed circuit
breaker (mechanical as well as electrical interlock);
 rolling-out of the carriage from a service position with closed
circuit breaker (mechanical as well as electrical interlock);
closing of the earthing switch in the cabinet case with a service
position of the carriage (mechanical as well as electrical interlock);
 rolling-in of the carriage into a service position with a closed
earthing switch (mechanical as well as electrical interlock).
 Isolation of power circuit in the Test and With-drawn position
(mechanical disengagement).
 Anti pumpingfeatureto prevent repeated closing.
 The circuit breaker can be rolled out of service position only if the
foot paddle is pressed and electromagnetic lock is released.
Pressing the foot paddle trips the circuit breaker mechanically.
 When circuitbreaker is in service position, earthing switch drive
blocking casing cannot be opened for inserting the rod of earthing
switch operation.
 When circuit breaker is in test position, earthing switch drive
blocking casing can be opened and rod can be inserted for
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operation of earthing switch.
 Bus bar earthing switch can be operated onlyif all the circuit
breakers are in test position.
6/0.4 kV Unit Auxiliary transformers:
UATis connected to same bus as the generator, stepping down voltage to feed
the auxiliary power system busses. Whenever the generator is running, the UAT
is supplying the auxiliary load.
Specification of Auxiliary transformers:
Type of transformer:
Rated capacity:
Rated primary/secondary voltage:
Rated frequency:
Vector group:
Percentage Impendence:
-For 1000 kVA:
-For 400kVA:
Class of Insulation:
Type of neutral earthing:
Dry type, 3 phase
1000 & 400 kVA
6/0.4 and 6/0-433 kV (for lighting)
50 Hz
Dynl1
8%
5.5%
Class "F
Solidly grounded
Figure -6
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GROUP – 2
TRANSFORMERS
Introduction:
The transformer is defined as a static electric device, consisting of a
winding and core. It transforms AC electrical power from one voltage to
another voltage at the same frequency by Electro-Magnetic Induction without
any physical contact of the winding. The transformer is a unique electrical
equipment which don't have any moving part and used in Transmission
&Distribution system to step up & step down the voltage.
Main application of transformers:
Transformers are used as
a) Transmission transformer- for stepping up the Generation Voltage of
16-24 kV to 220 or 400 kV or even higher kV for Power Evacuation
eg. Generator Transformer
b) For Distribution transformer-For Distribution of Power Supply,
EHV is stepped down to 6.6/1 1/33/66 kV using Step Down
Transformer.
eg. Sub station Transformers.
c) Transformer For Utilization/Aux. Power supply-Utilization of the
Power supply is done at 11/6.6/0.440 kV for supplyingthe power to
the loads/auxiliaries.
eg. Auxiliary Transformer/Distribution Transformer.
Types of Transformers:
Transformers are classified mainly as following depending on various
factors.
 Depending on Type of Applications transformers are classified as
Power transformers and Distribution transformers.
 Depending on No. of Phase transformers are classified as Single
phase and Three Phase transformers.
 Depending on Type of Construction transformers are classified as
Core type and Shell type. In Core Type Transformer windings
surround the limbs of the core but in Shell Type Transformer core
surrounds the major portion of the windings.
 Depending on Type of Winding transformers are classified as Two
winding and Three winding. Two Winding Transformer has One HV
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&One LV Windings
eg. Generator Transformer. Three Winding
 Transformer has One HV & Two LV Windings
eg.UAT/RAT/CSAT.
 Depending on application transformers are classified as Instrument
Transformers i.e. CT/VT.
Transformer windings:
a) Primary winding-The Winding to which Input Voltage is applied.
b) Secondary winding-The Winding to which the Loads are connected
or which delivers output.
c) Tertiary winding-The Winding provided to suppress the Harmonics
in case of Star/Star Connected Transformer eg. RAT/CSAT in
KKNPP.
Major Parts of a Transformer:
Main parts of transformers are as follows,
 Core: Cores are manufactured of High quality cold-rolled grain
oriented silicon steel laminations of-0.33 mm thickness. Silicon steel
raises the permeability of the material at low flux densities &thereby
reduces the hysteresis &eddy current losses. Core sheets are laminated
into sections to reduce the iron losses. Core shapes may be depending on
transformers as follows
 Single Phase Transformer: 2 or 3 leg Core
 Three Phase Transformer: or 5 Leg Core
When Transformers are of Large Capacities, 5 Leg Cores are used to
contain them within the Heights of Transport Limitations.
 Winding:Primary, secondary &tertiary.
 Transformer tank: Transformer Tank is made of High quality steel
Plate designed to withstand Vacuum to hold the transformer along with
 Coolant (Oil):In case of Oil filled Transformer it also serves as a surface
to radiate the heat from the Tanks to air.
 Cooler or radiators: These are made of high quality steal in which oil
is cooled by forced or natural circulation of air.
 Bushing:Bushings comprises of central conductor surrounded by
graded insulation. Bushing is necessary whenever conductor is taken out
through transformer tank. Simple porcelain insulator bushings are
generally used up to 20 kV class. Oil filled bushings are used for 33 kV
and above applications. For making bushing compact, synthetic resin
bonded condensor bushing are used for HV transformers. Condensor
bushing consists of a central conductor surrounded by alternate layers of
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insulating papers and tin foils, capacitance formed due to this result in
uniform stress distribution between conductor surface and earthed
flanges.
 Conservator: Conservator acts as an expansion tank designed to
receive the transformer oil flow as it expands or contracts due to thermal
cycling.
Transformer accessories:
Tap Changer: Tap changer is used to vary output voltage in within
designed limit. The objective of Tap Changer is for adjusting secondary
voltages incase of primary voltage variation. Tap changers are classified
as off load and on load tap changer. On load tap changer is generally
located in the HV side of the winding due to low current, finer control.
HV winding terminals are located outside & hence easy to take the
tapping terminals out
Buchholz Relay: Buchholz relay is provided to detect the incipient
faults of Transformers. Buchholz Relay is mounted between the Main
Tank and the Conservator & collects the escaping gases. In case of severe
fault i.e. short-circuit, Buchholz Relay acts as a sudden Pressure relay.A
large volume of gas is generated & immediately activates the second
float which trips the transformer
Whenever there is arc due to incipient fault, it causes decomposition of
Transformer oil which produces gases (containing more than 70% of
Hydrogen Gas) which being light rises upwards & tries to go to the
Conservator. As buchholz Relay is fitted in the pipe leading to the
Conservator, Gas gets collected in the Relay, If sufficient gas is collected,
a float is activated & gives an alarm signal
Breather: This is mounted on the Transformer Tank to absorb any
moisture from the outside air. Normally silica gel is used as moisture
separator tank. Silica gel is partially dipped in oil to arrest the dust.
Transformer Carriage/Wheels: Used for transportation.
Transformer Over Pressure Switch/Diaphragm or pressure
reducing device: Used for transformer protection.
Oil and winding temperature Indicators: Used for protection.
Oil level gauge: This is mounted on the Transformer Tank to indicate
the oil level.
22
Transformer Cooling:
Core and coil assembly heats up due to load and self losses of
transformer which releases heat to the surrounding insulating coolant
such as oil.
The wasted energy in the form of heat generated in transformers due to
the on going iron and copper losses must be carried away to prevent
excessive rise of temperature and injury to the insulation of the
conductors.
The cooling method used must be capable of maintaining a sufficiently
low average temperature. It must be capable of preventing and excessive
temperature rise in any portion of transformer and the formation of hot
spots. Core and coils of the transformer in oil and allowing free
circulation for the oil through oil ducts suitability located in the coil
structure. The heated oil will tend to rise to the top, thus setting upa
natural circulating current of oil within the tank. The oil in contact with
the tank in turn gives up its heat to the tank walls radiator and
surrounding air, in this manner, the temperature of the coil & core
assembly is held to safe limit.
Transformers are cooled by cooling medium like Air (Dry Type
Transformers), SF6Gas ( in SF6 Gas Transformers), Synthetic Oil,
Mineral Oil (in Oil Filled Transformers).
Transformer Losses:
Losses in transformer consist of mainly two types No-load & on load
losses.
a) No Load (Iron) Losses- Cetain losses occur in a transformer
regardless of the load when the unit is connected to a source of voltage.
These loses include core losses, copper losses in the primary winding
due to the flow of no-load current and electric losses in core. Eddy
current loss due to circulating currents in the core iron is also no-load
loss.
b) Load (Copper) Losses- Load losses are those which occur in a
transformer during carrying of load. These losses are called copper
losses. Load losses are due to power lost when the load current flows
through the resistance of both the windings.
Total losses consist of the sum of the load losses and the no- load losses.
These losses in transformers are converted in to heat which is power
loss.
23
Cooling System For Power Transformers of KK Project:
ONAF Cooling: Transformers with ONAF cooling system (type D) must
be equipped with the control panel for Automatic start up and shut down
of the electrical fan motors. Fans must be switched when the
temperature of upper oil layers reaches approximately 55° C or when the
rated current is reached in dependent of the temperature.
Fans must be switched off when the oil temperature is decreased to 50°
C and the load current is less than rated value.Fan may start even in
case transformers load is more than 50% of nominal value
The start up is made in groups of coolers; depending on the transformers
load.
OFAF Cooling: OFAF cooling transformers with OFAF cooling must
be equipped with the control panels for performing the following
function.
Automatic start up of the cooling system simultaneously with the
energisation of transformers. This start up is performed by
groups and coolers depending on transformers load.
Automatic switching off the cooling system when the
transformer is disconnected.
Manually operated control for each cooler.
Transformers at KKNPP:
 400/220 KV, Inter Connecting Transformer (ICT).
 24/6.3-6.3 KV, Unit Auxiliary Transformer (UAT)
 220/6.3 - 6.3 KV, Reserve Auxiliary Transformer (RAT)
 220/6.3-6.3 KV Common Station Auxiliary Transformer(CSAT)
 400/ 24 KV Generator Transformer (GT)
GENERATOR TRANSFORMER AND ITS BUS DUCT
24
UNIT AUXILIARY TRANSFORMER
RESERVE AUXILIARY TRANSFORMER
25
GROUP- 3
6KV INDUCTION MOTORS AND 380 V SWITCH GEAR
AND TRI-TYPE AUXILLARY TRANSFORMER
380V SWITCH GEAR:
380V switchgears are used for receiving and distributing power supply to
the loads of capacity above 10 kW to 200kW.
Following are the parameters of 0.38kV switchgear:
Type of switchgear
Metal clad, Draw out type
Rated voltage, kV
0.38/0.415
Rated continuous current of bus bars, A
1600
Rated short-circuit withstand current,
40 for 1s
kA(rms)
Material of the bus bars
Copper
Protection class
IP 52
Type of circuit breaker
Air circuit breaker (ACB)
Rated continuous current of CB:
-for incomer, A
1250
-for feeders above 10 kW, A
40, 50, 100,250,400,630
Rated short-circuit breaking current, kA(rms)
40
Type of operating mechanism
Motor operated spring
charged
Emergency mechanical trip
Provided
Type of releases
Numerical and electromagnetic
(for motors)
Rated auxiliary power supply voltage, V
220 DC/AC
Contactors used in 0.38kV switchgear for motor feeders
Type of contactor
Rated voltage, kV
Rated continuous current
Rated short circuit withstand current, kA
Rated control power supply voltage, V
Air break
0.3
40, 50, 100,250,400,630
40 for 1s
220 DC/ AC
Switchgears are made of combinations of several cabinets. Each cabinet
consists of the compartments; by assembling which in different combinations
and quantities any switchgear can be constructed. Each cabinet is divided into
the compartments compartment for bus bars, compartment housing circuit
26
breaker, protection, control, and measurement devices and compartment
forcable connections.
The construction of cabinets provides both double-sided and one-sided front.
0.38kV switchgear cubicles are equipped with air circuit breakers installed in
draw -out type modules for loads ofrating 11 kW and above up to and
including 200 kW.
The following devices of local control during testing and monitoring are
installed on front panels of switch-gear cabinets:
 Incoming supply live indicating R Y B lamps for incomers
 CB On-Off control switch
 CB On-Off indication lamps
 CB position status indication lamps (service, test, withdrawn).
 Voltmeter
 Ammeter
 Displays for signaling on actuation of protection devices
 Alarm for calling personnel into the room
 Remote control of from MCR and SCR
Interlocks and permissive
In order to prevent malfunctions of the electrical circuits by the operating
personal, the following provisions are to be made in the switchgear:
 0.38 kV switchgears are provided with limit switches on draw-out units
(carriages) with Test, Service and With-drawn positions.
 Mechanical interlocks to prevent draw-out and draw-in of the switching
cubicle when it is closed.
 Isolation of power circuit in the test and with-drawn position.
 Mechanical interlocks to prevent the draw-in of switching cubicle when
the grounding switch is closed.
 Electromagnetic interlocks to prevent 6kV switchgear energization of
grounded bus of system.
 Inter-locks to prevent the unauthorized access tothe operating switches
push buttons.
 Anti pumping feature to prevent repeated closing.
Electrical interlocks are provided to prevent access to live parts of assemblies.
This provides the safety of the personnel and integrity of the equipment.
27
In addition, the provision is made for:
 In case of the tripping of the o.38kV incomer of the normal power supply
on bus fault, automatic switching of stand-by power supply to the faulty
bus is prevented.
 In case of wrong disconnection by the operator ofthenormal auxiliary
power supply system incomer to 0.38kV bus or in case of disconnection
of 6/0.4 kV auxiliary transformer from 6kV bus, reserve power supply
incomer to the corresponding bus will operate automatically.
 In case of disturbance in 0.38kV outgoing feeders, the protective devices
provides certain time delay to keep 6/0.4kV auxiliary transformer in
operation and incomer power supply to 0.38kV bus available and will1
provide disconnection of the faulty feeder.
Motor control centers (MCCs):
MCC is a switchgear that is used for control of motors whose rating is less
than or equal to 11kW. Also, certain motors having rating more than 11kW
are controlled by MCCs in places where switchgears are not provided.
An MCC has
1. Power buses: power buses are of two types, Horizontal & Vertical:
2. The power output of the incomer feeder is fed to the Vertical bus
bar, which runs through out the whole length of that particular
MCC. From this vertical bus bar, outgoing feeders derive their
power supply, also this vertical bus bar is connected on the top to
the Horizontal bus bars, which carries the power supply to the near
by MCC.
3. Control buses: This supplies (EC & N5) the single phase control
voltage supply to the outgoing feeders & to the indications
available in the MCC panel via EH & EHA buses.
4. Incoming feeder (Main & Standby wherever applicable): The
supply from the SWGR comes to the incoming feeder & the
incoming feeder extends this power supply to the outgoing feeders
via vertical bus bars.
5. Control voltage feeder: This feeder receives the single phase
control supply required for controlling the outgoing feeders.
6. Under voltage feeder: This feeder trips the motor loads connected
to it if an under voltage takes place in the power supply bus.
7. Outgoing feeder: This feeder extends the power supply to
individual loads.
8. Cabinet heater: This provides for the heating of the MCC cabinet.
28
CIRCUIT BREAKER:
In 380V switch gear Air circuit breaker is used. Because,
 Less maintenance
 Low cost
 Less space is required
Figure -7
6KV INDUCTION MOTOR:
In KKNPP 46 6kV induction motors are used. High voltage motors are
produced because to reduce size of the motor to be compactive.
Figure -8
TRI-TYPE AUXILLARY TRANSFORMER:
To supply power to all load like pump, motor, cooling systems tri-type
auxiliary transformer is used.
Figure – 9
29
GROUP – 4
SICAM
SIEMENS
COMMUNICATION
CONTROLLING AND MONITORING
INSTRUMENT
FOR
SICAM:
Substation automation that sets the standards SICAM:The flexible control and
monitering system. It is used to minimize the work load.
RELAYS:
 6kV
 220V
In KKNPP the SICAM is used to control the control room for distributing the
generated power in unit 1 and unit 2. It stores the data and communicate to
control panel and act like an CPU.
The control room has the MCBs ,CPUs in panel called Mosaic Panel.
MOSAIC PANEL:
Mosaic Panel is the most user friendly, reliable and economical approach to
process visualization. It is suitable for all kinds of control and monitoring
indicator board, for process control, power networks, & security etc. it is used
for electrical components installation. It is easily replaceable.
Figure – 10
30
SICAM:
Figure – 11
OPTICAL CABELS:







XC-2 - Used to receive and send data.
A/D gaurds
Power block – Send power to interface.
F/O converter – Fiber optical converter.
RS 232
RS 485
Gate way – To send communication
In mosaic panel it consist of displays, relays, MCBS, CPUS, and the panel is
divided into 7 sets of panels for different controlling areas. Each of the panel are
grouped into 2 and it has 1central CPU and 5 control CPUS.
 The CPUs consist of 6mb memory card to store data.
 It is controlled through hardware.
31
GROUP – 5
SWITCH YARD
INTRODUCTION:
The main function of switchyard is to transmit & distribute the power at
incoming voltage from the generating station and provide facilities of switching
by the help of switchgears. Earlier we have explained about the various types of
switchgears in our previous article. Switchyard is the point in the power
network where transmission lines and distribution feeders or generating
units are connected through circuit breakers and other switchgears via bus bars
and transformers. Switchyard acts as interface between the power plant
electrical system and electrical grid.
Types of Switchyard:

AIS (Air Insulated Switchyard): This is the most common type of
switchyard. here the switchyard is present outside and open to the
atmosphere. The high voltage lines are isolated by the air, for that
reason they occupy more space as compared to the GIS.

GIS (Gas Insulated Switchyard): This type of switchyard is
generally found where the space available is very less and they are
generally located inside a closed room with proper isolation. The high
voltage cables are kept inside the duct with insulation. At KKNPP GIS
is used.
Figure – 12
32
Components of Switchyard
Gantry Structures: Gantry structures are made of steel and are used to support
high voltage conductors throughout the substations that interconnect sections of
electrical equipment. In general there are two types of gantry structures and out
of them Tubular gantry is mostly used in switchyards as it takes lesser time for
installation and easy to install.
Bus-bar: Bus-bars receive the power from incoming circuits or we can say a
grid and deliver the power to an outgoing Circuit. It can be single phase or three
phases, but most of the cases it is 3-phase and one bus consists of 3
conductors(R-Y-B).There are also various types of bus bar arrangements
depending upon their requirements. The various arrangements are mentioned
below:
Single Bus System: This type of bus arrangement is the cheapest and the
simplest one. In this scheme all the feeders and transformers are connected to
only one single bus as shown below. The major disadvantage of this kind of
system is that for the maintenance of the breakers and other equipment we have
to isolate all the systems and keep it in offline. This scheme is generally
employed for the gas insulated switchyards and another disadvantage is that if
you are going for maintenance then the respective transformer or feeder should
be disconnected.
Single Bus System with Bus-sectionalizer: In this type of arrangement the
main bus is divided into two different circuits by the help of a circuit breaker.
The advantage of this kind of arrangement is that if one section of the bus bar is
under maintenance then the other part of the system, which is isolated by the
bus-coupler or bus-sectionalizer, is kept energized, but here also if we are going
for maintenance on any breaker then the respective feeder or the transformer has
to be disconnected.
Double Bus System: In this arrangement, two identical bus bars will be there,
one as Main Bus-1 and the other as Main Bus-2.Here both the buses are
connected through a bus coupler. The bus coupler does two works during line
charging it matches the voltage level of both the lines and connect both the
lines. Here the flexibility of the system is increased as another bus-bar acts as a
backup for the other bus-bar, but here also without any interruption we can’t go
for the maintenance.
33
One And A Half Breaker Scheme: This is the most advanced and widely used
scheme in modern power plants. In this type of scheme
Two feeders are connected to two different buses through their circuit breakers
respectively and these two feeders are connected by a third breaker as a tie
breaker. During failure of any feeder breaker, the third breaker comes into play
and transfers power to the other feeder. This scheme increases the availability of
the feeder during maintenance or failure of the other feeder. If there is some
fault on the Bus-1 then also without tripping the units we can continue the
power flow by the help of the tie-breaker.
Insulator: The insulators mainly serve two purposes. First of all they support
the conductor and confined the high current of the line to the conductor. The
most common material for the manufacturing of insulators is Porcelain. Below
mentioned are the types of Insulators used in switchyard,

Pin Insulator

Post Type

Suspension Insulator

Strain Insulator
Post type and strain type insulators are mostly used in switchyard.
Surge Arrester: This will protect the equipment from transient, surge and high
voltages. They are generally connected in parallel to the equipment to be
protected and function to divert the surge current safely to ground.
Isolator: Isolators are generally no- load switches which are used to isolate the
electrical lines during maintenance. They are only operated for isolation after
the circuit breaker is operated. They are operated by means of a motor present
below the isolator assembly.
Earth switches on Isolator: Earth Switch is used to discharge the residual
charge on the circuit to the earth safely. Earth switch is mounted on the frame of
the isolators. After the equipment is isolated then the earth rod is connected so
that the residual charges present on the device will be grounded. This is mainly
done for safeguarding human life from getting a shock.
Wave trap: Wave trap is a resonant circuit connected in series with the HV
transmission line to prevent the transmission of high frequency signals. The
communication wave is having a high frequency of 150 KHz to 200 KHz and
the electrical power has a frequency of 50 Hz. So to avoid the communication
34
waves to travel to the electrical equipment we are using this Wave-trap. It
creates a high reactance path for the High –frequency signal and blocks it. We
are employing these Wave-traps is due to the use of PLCC (Power Line Carrier
Communication).
PLCC: PLCC stands for Power Line Carrier Communication. This technology
is used in all sub-stations for communication with other sub-stations. The
information regarding the generation and other parameters are transmitted to
other sub-stations or grid by the help of this PLCC. By the help of PLCC, we
are avoiding the use of an extra wire for communication and the information
flows through the transmission lines and it is much faster than any other
medium.
Circuit breaker: A circuit breaker is equipment which can make and break a
circuit under normal as well as during fault conditions. It is operated during on
load condition and the arc generated while opening the circuit is quenched by a
strong di-electric medium. The most widely used arc quenching mediums for
HV Lines are Vacuum and SF6 Gas.
Current transformer: Basically this is a step down transformer which is used
for measuring purpose as well as protection purpose. For both these purposes
the CTs are designed with different types of core. For measuring purpose, the
CT saturation point is given at ankle point on the characteristic curve between
the Flux (⌀) and current (I) and for the Protection purpose the saturation point is
given at ankle point of the curve. The CTs generally have a ratio of 100:1 or
200:1 so that they will reduce the transmission line current to a very lower value
suitable for measurement and relay protection (around 5 to 4 Amps).These are
connected in series with the transmission line.
Potential transformer: Potential transformers are used to step down the line
voltages up to measurable quantity 110v from any voltage level (for
measurement of voltage).They are connected in parallel with the transmission
line.CTs and PTs almost look alike, but depending upon their connections we
can distinguish them.
Protective relay: A protective relay is a device that detects the fault and
initiates the operation of the Circuit breaker to isolate the faulty element from
the rest of the system. Whenever there is a fault in the bus,the relay senses it and
gives the command to the circuit breaker and the circuit breaker is operated. The
relay receives the command from the instruments transformers (i.e CTs & PTs).
35
GAS INSULATED SUBSTATION (GIS):
A gas insulated substation is an electrical substation in which the major
structures are contained in a sealed environment with sulphur hexafluoride gas
as the insulating medium.
Figure -13
 In KKNPP GIS of 12 bay and 6 dia are was installed.
 For 1 breaker 2 disconnectors are used to disconnect the breaker.
 The SF6 circuit breaker is used in GIS.
 The SF6 density meter measures the required pressure level, if the
pressure goes down the density meter alert the circuit breaker to break.
 Hydraulic cubicle – Maintain the oil level of circuit breaker.
BELLOWS:
The bellows is a one-piece, collapsible, seamless metallic unit that has deep
folds formed from very thin-walled tubing. System or line pressure is applied to
the internal volume of the bellows. As the inlet pressure to the instrument
varies, the bellows will expand or contract.
36
Figure -14
CONTROL ROOM:
A control room is a central space where a large physical facility or
physically dispersed service can be monitored and controlled. It is
often part of a larger command centre.
Figure - 15
37
Unit supplied-1000 MW
Supply to grid from switch yard
DISTRIBUTION PANELS
Mosaic panels or Mimic panels are used to hold the control
components of the distribution equipments. Each of them are noted
with separate codes.
ACL21,ACL22,ACL23 – Supply to Tirunelveli.
ACL13,ACL31 – Supply to Tuticorin.
ADL15 – Supply to SR Puthoor
1 breaker is used between 3 buses it is called 1 ½ scheme.
38
GROUP-6
UPS
UNINTERRUPTIBLE POWER SUPPLY
INTRODUCTION:
Uninterruptible power supply provides backup power, protecting equipment
from damage in the event of grid power failure. It is a type of device that
powers equipment, nearly instantaneously, in the event of grid power failure.
AC
Figure –16
RECTIFIER:
A Rectifier is an electrical device that converts alternating current, which
periodically reverse direction, to direct current, which flows in only one
direction by rectifying the direct current. This process is known as rectification.
At KKNPP (220V/630A) is used.
Figure – 17
39
INVERTERS:
Inverters are also called AC drives, or VFD (variable frequency drive). They are
electronic devices that turn DC to AC. At KKNPP (220V/60KVA) inverter is
used.
Figure – 18
BATTERY:
A battery is a device that converts chemical energy contained within its active
materials directly into electric energy by means of an electrochemical oxidationreduction reaction. This type of reaction involves the transfer of electrons from
one material to another via an electric circuit.
Figure – 19
40









At KKNPP Lead acid Battery is used store the backup energy to reactor.
At KKNPP 38 UPS BANK and 38 BATTERY BANKS are allocated.
Each of the bank contains 106 cells of Batteries.
1 Battery has the capacity of 2 volt.
They are connected in series connection.
Monthly checking will taken.
Hydrometer is used to measure the Volt, Specific Gravity of the Battery.
Specific Gravity = Density of any item/Density of water.
To check the temperature level of the battery (Alcoholic Thermometer )is
used.
 Distilled water is used as the medium for batteries.
41