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2. 132/11 KV SUBSTATION

3. INDEX
• Introduction
• Classified of substation
• Single line diagram
• Lighting arrester
• Capacitor voltage transformer(CVT)
• Current transformer
• Potential transformer
• Circuit breaker

4. INDEX
• Relay
• Bus
• Transformer
• Working
• Control panel
• Battery
• Isolator

5. INTRODUCTION
• The present-day electrical power system is A.C.
i.e. electric power is generated, transmitted and
distributed in the form of alternating current.
• It is delivered to the consumers through a large
network of transmission and distribution.
• At many places in the line of the power system, it
may be desirable and necessary to change some
characteristic (e.g. voltage, A.C. to D.C., frequency,
Power factor etc.) of electric supply.

6. • This is accomplished by suitable apparatus
called sub-station. For example, generation
voltage (11KV or 6.6KV) at the power station is
stepped up to high voltage (say132KV or
220KV) for transmission of electric power.
• The assembly of apparatus (e.g. transformer
etc.) used for this purpose is the sub-station.
• Similarly, near the consumer’s localities, the
voltage may have to be stepped down to
utilization level.
• This job is again accomplished by a suitable
apparatus called ‘substation’.

7. TYPE OF SUBSTATION
There are several ways of classifying sub-stations.
However, the two most important way is used to make
substation.
According To The Requirements:- A sub-station
may be called upon to change voltage level or improve
power factor or convert A.C. power into D.C. power etc.
According to the service requirement, sub-stations
may be classified into:
1. Transformer sub-stations
2. Switching sub-stations
3. Converting sub-stations
4. Industrial sub-stations

8. According To The Constructional Features
• A sub-station has many components (e.g.
circuit breakers, switches, fuses, instruments
etc.) which must be housed properly to ensure
continuous and reliable service. According to
constructional features, the sub-stations are
classified as
1.Indoor sub-station
2.Outdoor sub-station
3.Underground sub-station

9. SINGLE LINE DIAGRAM

10. LIGHTENING ARRESTOR
• Lightening arresters are the instruments that are used
in the incoming feeders so that to prevent the high
voltage entering the main station. This high voltage is
very dangerous to the instruments used in the
substation. Even the instruments are very costly, so to
prevent any damage lightening arresters are used. The
lightening arresters do not let the lightening to fall on
the station. If some lightening occurs the arrestors pull
the lightening and ground it to the earth. In any
substation the main important is of protection which is
firstly done by these lightening arrestors. The
lightening arresters are grounded to the earth so that it
can pull the lightening to the ground.

11. FIGURE OF L.A
(i) Surge Diverter
(ii)Characteristics of The Non Linear Resister Lightning Arrester

12. WORKING OF L.A.
• Under normal operation, the lightning arrester is off the line
i.e. it conducts no current to earth or the gap is non-conducting.
• On the occurrence of over voltage, the air insulation across the gap
breaks down and an arc is formed providing a low resistance path for
the surge to the ground. In this way, the excess charge on the line due
to the surge is harmlessly conducted through the arrester to the
ground instead of being sent back over the line.
• It is worthwhile to mention the function of non-linear resistor in the
operation of arrester. As the gap sparks over due to over voltage, the
arc would be a short circuit on the power system and may cause
power-follow current in the arrester. Since the characteristic of the
resistor is to offer low resistance to high voltage (or current), it gives
the effect of short circuit. After the surge is over, the resistor offers
high resistance to make the gap non conducting.

13. CPPACITOR VOLTAGE TRANSFORMER
• A capacitor voltage transformer (CVT) is a transformer
used in power systems to step-down extra high voltage
signals and provide low voltage signals either for
measurement or to operate a protective relay.
• These are high pass Filters (carrier frequency 50KHZ to
500 KHZ) pass carrier frequency to carrier panels and
power frequency parameters to switch yard.
• In its most basic form the device consists of three
parts: two capacitors across which the voltage signal is
split, an inductive element used to tune the device and
a transformer used to isolate and further step down
the voltage.

14. FIGURE OF C.V.T
Circuit Diagram of C.V.T Capacitor Voltage Transformer

15. WORKING OF C.V.T
• The device has at least four terminals, a high-voltage
terminal for connection to the high voltage signal, a
ground terminal and at least one set of secondary
terminals for connection to the instrumentation or
protective relay. CVTs are typically single-phase devices
used for measuring voltages in excess of one hundred
KV where the use of voltage transformers would be
uneconomical. In practice the first capacitor, C1, is
often replaced by a stack of capacitors connected in
series. This results in a large voltage drop across the
stack of capacitors, that replaced the first capacitor and
a comparatively small voltage drop across the second
capacitor, C2, and hence the secondary terminals.

16. WAP TRAP
• Wave trap is an instrument using for trapping of
the wave.
• The function of this wave trap is that it traps the
unwanted waves. Its shape is like a drum.
• It is connected to the main incoming feeder so
that it can trap the waves which may be
dangerous to the instruments in the substation.
• Generally it is used to exclude unwanted
frequency components, such as noise or other
interference, of a wave.

17. • Line trap also is known as Wave trap.
• What it does is trapping the high frequency
communication signals sent on the line from
the remote substation and diverting them .
• The telecom/ tele protection panel in the
substation control room through coupling
capacitor.

18. CURRENT TRANSFORMER
• Current transformer is a
current measuring device
used to measure the currents
in high voltage lines directly
by stepping down the
currents to measurable
values by means of
electromagnetic circuit.

19. WORKING PRINCIPLE OF C.T
• The basic principle induced in designing of current transformers is-
• Primary ampere turns = Secondary ampere turns
• Ip Np = Is Ns
• Where, Ip - Primary current
• Np – Primary Winding Turns
• Is - Secondary Current; Ns – Secondary Winding Turn
• Ampere turns plays very important role in designing current
transformers.
• Current transformers must be connected in series only.
• Current transformer has less no of turns in primary and more no of
turns in secondary.
• The secondary current is directly proportional to primary current.

20. POTENTIAL TRANSFORMER
• An instrument transformer in which the
secondary voltage.
• in normal conditions of use ,it is substantially
proportional to the primary voltage and differs
in phase from it by an angle.
• which is approximately zero for an appropriate
direction of the connections.

21. WORKING OF P.T
• The basic principle involved in the designing of Voltage Transformer
is-
• Voltage Ratio = Turns Ratio
• VP / VS = NP / NS
• Thus NS VP = NP VS
• As heavy primary voltages will be reduced to low secondary
voltages.
• it will have more turns in the primary & less turns in the secondary.
• It must always be connected in parallel only.
• Even if we connect it directly from high voltage to earth, it is not
going to be a short circuit as its primary winding has very high
resistance. Its core is a set of assembled laminations.

22. FIGURE OF P.T
Potential Transformer
Line Diagram of VT.

23. CIRCUIT BREAKER
• The circuit breakers are used to break the
circuit if any fault occurs in any of the
instrument.
• These circuit breaker breaks for a fault which
can damage other instrument in the station.
• For any unwanted fault over the station we
need to break the line current.
• This is only done automatically by the circuit
breaker.

24. CIRCUIT BREAKER TYPE
The present trend is up to 33KV, VCBs are
preferred and beyond 33KV, SF6 gas
circuit breakers are preferred.
There are mainly two types of circuit breakers
used for any substations. They are
(a) SF6 circuit breakers,
(b) Vacuum circuit breakers.

25. SF6 CIRCUIT BREAKER
• Sulphur hexafluoride (SF6) is an inert, heavy gas having
good dielectric and arc extinguishing properties.
• The dielectric strength of the gas increases with
pressure and is more than the dielectric strength of oil
at 3 kg/cm2.
• SF6 is now being widely used in electrical
• equipment like high voltage metal enclosed cables;
high voltage metal clad switchgear, capacitors, circuit
breakers, current transformers, bushings, etc.
• The gas is liquefied at certain low temperature,
liquidification temperature increases with the pressure.

26. PROPERTY OF SF6
Some of the properties of SF6 are,
• Very high dielectric strength
• High thermal and chemical inertia
• Superior arc extinguishing
• capability
• Low decomposition by arcing

27. BUS
• The bus is a line in which the incoming feeders come into
and get into the instruments for further step up or step
down.
• The first bus is used for putting the incoming feeders in la
• single line.
• There may be double line in the bus so that if any fault
occurs in the one the other can still have the current and
the supply will not stop.
• The two lines in the bus are separated by a little distance by
a conductor having a connector between them.
• This is so that one can work at a time and the other works
only if the first is having any fault.

28. TRANSFORMER
• Transformers come in a range of sizes from a thumbnail-sized
coupling transformer.
• hidden inside a stage microphone to huge units weighing
hundreds of tons used to interconnect portions of national
power grids.
• All operate with the same basic principles, although the range
of designs is wide.
• While new technologies have eliminated the need for
transformers in some electronic circuits, transformers are still
found in nearly all electronic devices designed for household
("mains") voltage.
• Transformers are essential for high voltage power
transmission, which makes long distance transmission
economically practical .

29. BASIC PRINCIPLE OF TRANSFORMER
• The transformer is based on two principles:
• firstly, that an electric current can produce a
magnetic field (electromagnetism) and secondly
that a changing magnetic field within a coil of
wire induces a voltage across the ends of the coil
(electromagnetic induction).
• Changing the current in the primary coil changes
the magnetic flux that is developed.
• The changing magnetic flux induces a voltage in
the secondary coil.

30. Induction law
which states that, where VS is the
instantaneous voltage, NS is the number
of turns in the secondary coil and Φ equals the
magnetic flux through one turn of the coil.
If the turns of the coil are oriented
perpendicular to the magnetic field lines, the
flux is the
product of the magnetic field strength and the
area A through which it cuts. The area is
constant, being equal to the cross-sectional
area of the transformer core, whereas the
magnetic
field varies with time according to the
excitation of the primary.

31. CAPACITOR BANK ATTACHED TO THE
BUS
• The capacitor banks are
• used across the bus so that the
• voltage does not get down till at
• the require place.
• A capacitor bank is used in the
• outgoing bus so that it can
• maintain the
• voltage level same in the
• outgoing feeder.

32. Capacitor Control Is Usually Done To
Achieve The Following Goals
• Reduce losses due to reactive load current.
• Reduce KVA demand, decrease customer energy
consumption.
• Improve voltage profile, and increase
• revenue.
• Indirectly capacitor control
also results in longer equipment
lifetimes because of reduced
equipment stresses.

33. TRANSFORMER PROTECTION
• Station Transformer: HG Fuse protection on HV side and fuse protection
on LV side and Vent pipe.
• Power transformers up to 7.5MVA:
• HV side: O/L & Directional E/L protection with highest element in O/L
relays.
• LV side: O/L & E/L protection Buchholz Relay OLTC Buchholz Relay
• Power transformers from 8.0MVA and above: HV side O/L & Directional
E/L
• protection with high set element in O/L relays. LV side O/L & E/L
• protection: differential protection Buchholz Relay OLTC Buchholz Relay
OTI, WTI
• and PRV.
• Power transformers from 31.5MVA and above: Over flux protection & LV
WTI in
addition to protection.

34. FEEDER PROTECTION
• 33KV feeders: Non directional O/L & E/L
protection with highest and IDMT characteristics.
• 132KV feeders: Main protection: Distance
protection. Back up protection: Directional
• O/L & E/L protection.
• 220KV feeders: Main-1 protection: Distance
protection Main-2protection: Distance
protection, LBB protection, pole discrepancy
Relay.

35. isolator
• Isolator is a mechanical switch which isolates
a part of circuit from system as when
required. Electrical isolators separate a part of
the system from rest for safe maintenance
works.

36. THANK
YOU!