1. INTRODUCTION 220 KV GRID is located in Devigarh, Patiala .The grid receives 220 KV lines and steps down further into 66 KV and 11 KV lines .The 66KV Grid was setup in the year 1973 and it is modified to 220KV up to Feb 2014The various components used for stepping down the voltage and protection are installed in the grid like transformers , circuit breakers, relays , current transformers ,potential transformers ,battery bank, busbar, lightning arrestor , insulators ,capacitor banks and various other sensors and devices. Incoming Feeder:- 220KV Bhateri(Bhadurgarh) Outgoing Feeder:- 66 KV 1. Bhunerheri 2. Magar Sahib 3. Rohar Jagir 11 K.V. 1. Jhawalapur 10. S.S.Wala 2. Mehon 11. Dudhan 1
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1. INTRODUCTION
220 KV GRID is located in Devigarh, Patiala .The grid receives 220 KV lines and steps down
further into 66 KV and 11 KV lines .The 66KV Grid was setup in the year 1973 and it is
modified to 220KV up to Feb 2014The various components used for stepping down the
voltage and protection are installed in the grid like transformers , circuit breakers, relays ,
current transformers ,potential transformers ,battery bank, busbar, lightning arrestor ,
insulators ,capacitor banks and various other sensors and devices.
Incoming Feeder:-
220KV Bhateri(Bhadurgarh)
Outgoing Feeder:-
66 KV
1. Bhunerheri
2. Magar Sahib
3. Rohar Jagir
11 K.V.
1. Jhawalapur 10. S.S.Wala
2. Mehon 11. Dudhan
3. Bangra 12. UPS-01
4. Kisanpur 13. UPS-02
5. Partapgarh 14. UPS-03
6. Hasanpur 15. Binjal
7. Masingan 16. Julkhan
8. Shekhupur 17. Gagrola
9. Bhunerheri 18. Waliyan
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NEED OF PROJECT WORK
The project entitled “STUDY OF VARIOUS COMPONENTS USED IN 220 KV
DEVIGARH GRID AND PROTECTION ,MAITENANCE OF POWER TRANSFORMER”
was carried out to have deep and sound knowledge of what are the various components used
in the grid , how are the various components installed , what is the use of the various
components , how do these components work etc . It also gave a knowledge of how the
power transformer operate, its protection, maintenance and lot of other things related to
transformer. This project made me aware of all these things.
Our main purpose for this visit is to be familiar with industrial environment and to get
practical knowledge of electrical power transmission and distribution Students of 3rd
semester will get the idea of electrical power transmission and distribution.
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2. SUBSTATION
An electrical sub-station is an assemblage of electrical components including busbars,
switchgear, power transformers, auxiliaries etc.
These components are connected in a definite sequence such that a circuit can be switched off
during normal operation by manual command and also automatically during abnormal
conditions such as short-circuit. Basically an electrical substation consists of No. of incoming
circuits and outgoing circuits connected to a common Bus-bar systems. A substation receives
electrical power from generating station via incoming transmission lines and delivers elect.
power via the outgoing transmission lines.
Sub-station are integral parts of a power system and form important links between the
generating station, transmission systems, distribution systems and the load points.
Fig 2.1 Graphical view of 220 KV Grid
MAIN TASKS
Associated with major sub-stations in the transmission and distribution system include the
following:
1. Protection of transmission system.
2. Controlling the Exchange of Energy.
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3. Ensure steady State & Transient stability.
4. Load shedding and prevention of loss of synchronism. Maintaining the system
frequency within targeted limits.
5. Voltage Control; reducing the reactive power flow by compensation of reactive power,
tap-changing.
6. Securing the supply by proving adequate line capacity.
7. Data transmission via power line carrier for the purpose of network monitoring; control
and protection.
8. Fault analysis and pin-pointing the cause and subsequent improvement in that area of
field.
9. Determining the energy transfer through transmission lines.
10. Reliable supply by feeding the network at various points.
11. Establishment of economic load distribution and several associated functions.
TYPES OF SUBSTATION
The substations can be classified in several ways including the following :
1. Classification based on voltage levels, e.g. : A.C. Substation : EHV, HV, MV, LV;
HVDC Substation.
2. Classification based on Outdoor or Indoor : Outdor substation is under open skv.
Indoor substation is inside a building.
3. Classification based on configuration, e.g. :
Conventional air insulated outdoor substation or
SF6 Gas Insulated Substation (GIS)
Composite substations having combination of the above two
4. Classification based on application
Step Up Substation : Associated with generating station as the generating voltage
is low.
Primary Grid Substation : Created at suitable load centre along Primary
transmission lines.
Secondary Substation : Along Secondary Transmission Line.
Distribution Substation : Created where the transmission line voltage is Step Down
to supply voltage.
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Bulk supply and industrial substation : Similar to distribution sub-station but
created separately for each consumer.
Mining Substation : Needs special design consideration because of extra
precaution for safety needed in the operation of electric supply.
Mobile Substation Temporary requirement.
NOTE :
Primary Substations receive power from EHV lines at 400KV, 220KV, 132KV
and transform the voltage to 66KV, 33KV or 22KV (22KV is uncommon) to suit
the local requirements in respect of both load and distance of ultimate consumers.
These are also referred to ‘EHV’ Substations.
Secondary Substations receive power at 66/33KV which is stepped down usually
to 11KV.
Distribution Substations receive power at 11KV, 6.6 KV and step down to a volt
suitable for LV distribution purposes, normally at 415 volts.
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3. LIGHTNING ARRESTOR
Lighting arrestor is a device, which protects the overhead lines and other electrical apparatus
viz , transformer from overhead voltages and lighting When the positively charged cloud
produce negative charge on the overhead line by electrostatic induction then the negative
charge is however presented right under the cloud and portion of the line away from the cloud
becomes positively charged This charge on the line does not flow
Every instrument must be protected from the damage of lighting stroke. The three protection
sin a substation is essential:-
Protection for transmission line from direct strokes
Protections of power station or substation from direct strokes
Protection of electrical apparatus against traveling waves
Effective protection of equipment against direct strokes requires a shield to prevent lighting
from striking the electrical conductor together with adequate drainage facilities over insulated
structure.
Installation Location :-
Install arrester electrically as close as possible to the appearatus being protected Line and
ground connections should be short and direct
Fig 3.1 Lightning Arresters
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Grounding:-
The arrester ground should be connected to the apparatus grounds and the main station
ground utilizing a reliable common ground network of low resistance. The efficient operation
of the lightning arrester requires permanent low resistance grounds : Station class arresters
should be provided with a ground of a value not exceeding five ohms.
Clearances:- These are given on the drawings. These are the maximum recommended. The
term ‘clearance’ means the actual distance between any part of the arrester or disconnecting
device at line potential, and any object at ground potential or other phase potential.
It consist of a isolator in series and connected in such a way that long isolator is in upward
and short isolator is in downward so that initially large potential up to earth is decreased to
zero
An ideal arrestor must therefore have the following properties:
1. It should be able to drain the surge energy from the line in a minimum time
2. Should offer high resistance to the flow of power current
3. Performance of the arresters should be such that no system disturbances are
introduced by its operation
4. Should be always in perfect from to perform the function assigned to it
5. After allowing the surge to pass, it should close up so as not to permit power current
to flow to ground
Fig 3.2 Lightning Arresters
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Working:-
Lightning, is a form of visible discharge of electricity between rain clouds or between a rain
cloud and the earth The electric discharge is seen in the form of a brilliant arc, sometimes
several kilometres long, stretching between the discharge points How thunderclouds become
charged is not fully understood, but most thunderclouds are negatively charged at the base
and positively charged at the top However formed, the negative charge at the base of the
cloud induces a positive charge on the earth beneath it, which acts as the second plate of a
huge capacitor
When the electrical potential between two clouds or between a cloud and the earth reaches a
sufficiently high value (about 10,000 V per cm or about 25,000 V per in), the air becomes
ionized along a narrow path and a lightning flash results.
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4. WAVE TRAP
It is used to trap the communication signals & send PLCC room through CVT. Rejection
filters are known as the line traps consisting of a parallel resonant circuit ( L and C in
parallel) tuned to the carrier frequency are connected in series at each and of the protected
line such a circuit offer high impedance to the flow of carrier frequency current thus
preventing the dissipation. The carrier current used for PLC Communication have to be
prevented from entering the power equipments such as attenuation or even complete loss of
communication signals. For this purpose wave trap or line trap are used between transmission
line and power station equipment to avoid carrier power dissipation in the power plant reduce
cross talks with other PLC Circuits connected to the same power station. Ensure proper
operating conditions and signal levels at the PLC transmit receive equipment irrespective of
switching conditions of the power circuit and equipments in the stations.
Line matching filter and protective equipment:-
For matching the transmitter and receiver unit to coupling capacitor and power line matching
filters are provided. These flitters normally have air corral transformers with capacitor
assumed.
The matching transformer is insulated for 7-10 KV between the two windings and perform
two functions. Firstly, it isolates the communication equipment from the power line.
Secondly, it serves to match .
Transmitter:-
The transmitter consists of an oscillator and a amplifier. The oscillator generates a frequency
signal with in 50 to 500 HZ frequency bands the transmitter is provided so that it modulates
the carrier with protective signal. The modulation process usually involves taking one half
cycle of 50 HZ signal and using this to create block to carrier.
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Fig 4.1 Wave Trap
Receivers:-
The receivers usually consist of and alternate matching transformer band pass filter and
amplifier detector.
The amplifier detector converts a small incoming signal in to a signal capable of operating a
relatively intensive carrier receiver relay. The transmitter and receiver at the two ends of
protected each corresponds to local as far as transmitting.
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5. ISOLATOR
When carrying out inspection or maintains work in substation ,it is essential to disconnect
reliability the unit of other station on which the work is done from all other parts on
installation in order to ensure full safety of working staff .So guard against mistake it is
desirable that should be done by an apparatus is called “ISOLATOR”. In other words a
device which is used to open or close the circuit either when negligible current is interrupted
or when no significant change in voltage across the terminal of each pole of the isolator will
result from operation .they must only be opened or closed when current is zero. There is
single ear thing Isolator used .
Isolator is switching device used to open (or close) a circuit either when a negligible current
exists or when no significant change in voltage across the terminal of each pole of the
isolator, will result from the operation. Broadly speaking isolator are the switches which’s
operate under "No current” condition.
Fig 5.1 View of Isolator
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Isolators are file with earthing blades as an integral part of it. They may be isolators with
single ear thing blades or two earthling blades on either side of it.They must only be opened
or closed when current is zero. Isolators are classified into following categories.
1. Bus isolator
2. Line isolator
3. Transformer isolating switch
From constructional point of view the isolator may be classified as-
1.The post- centre post rotating part, double post break type.
2.Two post single type.
3.Base: - Each pipe phase isolator is mounted on a robust base of steal construction.
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6. POTENTIAL TRANSFORMER
There are two types of instrument transformer:-1. Potential Transformer
2. Current Transformer
Potential Transformer:-
Similar to CT it is another type of instrument type of instrument transformer .Transformer
used for voltage measurements are called voltage transformer or Potential transformer. it may
be of 1 phase or 3 phase
These transformers make the instruments suitable for measurement of high voltage and
isolating then from high voltage. these TX. Are connected in parallel and secondary winding
is always open ckt.
The primary has large no of turn in secondary,which provided step down of voltage , and
then the voltmeter is connected across secondary terminal the high voltage line.Some terms
related to PT :-
1. Rated voltage :- the capacity voltage of the PT which it can stand
2. Rated transformer ratio:- The ratio of the rated primary voltage to the rated second voltage.