220kV substation

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SUBSTATION
 A station in the power transmission system at which electric
power is transformed to a conveniently used form.
 The station may consist of transformers, switches, circuit
breakers and other auxiliary equipment.
 Its main function is to receive energy transmitted at high
voltage from the generating station, by either step-up or step-
down the voltage to a value appropriate for local use and
provide facilities for switching.
 Some substation, such as power plant switchyard are simply
switching stations where different connections can be made
between various transmission lines.

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Type of substation

 Step Up Substation
 Primary Grid Substation
 Secondary Grid Substation
 Distribution Substation
 Bulk Supply Substation

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Feeders

 Incoming Feeders:
➢ Bassi(220 KV)
➢ Heerapura(220 KV)
 Outgoing Feeders:
➢ Sitapura(132 KV)
➢ Puranaghat(132 KV)

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Typical Components of a Power
Plant Substation (Switchyard)

• CONNECT •A - Busbar

• CONNECT & DIS-CONNECT •B - Disconnector

• CONNECT, DIS-CONNECT & DETECT •C - Circuit Breaker

• DETECT & TRANSFORM •D - Current Transformer

• DETECT & TRANSFORM •E - Voltage Transformer

• PROTECT & SAFETY •F - Earthing Switch

• PROTECT •G - Surge Arrestor

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BUSBAR

 This is a term we use for a main bar

or conductor carrying an electric
current to which many connection
may be made. Busbars
(long heavy
 Buses are merely convenient tube type)
means of connecting switches
and other equipment into various
arrangements.
 Aluminum or copper conductors
supported on porcelain insulators,
carry the electric energy from
point to point.

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DISCONNECTS
Disconnect Switch
( moving contact rod (A) &
 This is an easily removed piece of contacts with flexible
fingers (B) )
the actual conductor of a circuit.
 The purpose of disconnects is to
isolate equipment.
 A typical use of disconnects is to
isolate a circuit breaker by
installing one disconnect on either
side of the circuit breaker (in series
with the breaker).

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CIRCUIT BREAKER
 This is used to interrupt circuits while
current is flowing through them.
Operating
 The operation of the breaker is very rapid Mechanism
Panel
when opening.
Circuit Breakers
 Circuit breakers of this type are usually ( Connected in a typical 3-
arranged for remote electrical control phase circuit )
from a suitably located switchboard.
 Some recently developed circuit
breakers have no oil, but put out the arc
by a blast of compressed air these are
called air circuit breakers.
Position
Indicator

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CURRENT TRANSFORMER

 Current transformer are used with

ammeters, watt meters, power-factor
meters, watt-hour meters, compensators,
protective and regulating relays and the
trip coil of circuit breakers.
 One current transformer can be used to
operate several instruments, provided
that the combined burden does not
exceed that for which the transformer is
designed and compensated.
 The current transformer is connected
directly in series with the line.

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VOLTAGE TRANSFORMER
 This is also know as potential transformer
used with volt-meters, wattmeter's, watt-
hour meters, power-factor meters,
frequency meters, protective and
regulating relays and the no-voltage and
over-voltage trip coils of automatic circuit
breakers.
 One transformer can be used for a number
of instruments at the same time if the total
current taken by the instrument does not
exceed that for which the transformer is
designed and compensated.
 The ordinary voltage transformer is
connected across the line, and the
magnetic flux in the core depends upon
the primary voltage.

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EARTHING SWITCH
 This is also known as ground disconnect, which used to
connects the equipment to a grid of electrical conductors
buried in the earth on the station property.
 It is intended to protect people working on the grounded
equipment.
 It does this by completing a circuit path, thereby reducing the
voltage difference between the equipment and its
surroundings.

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SURGE ARRESTOR
• These are devices used to provide the necessary
path to ground for such surges, yet prevent any
power current from following the surge. An ideal
arrester must therefore have the following properties:
1. Ability to remove the surge energy
from the line in a min. time.
2. High resistive to flow of power current.
3. A valve action automatically allowing
surge to pass and then closing up so
as not to permit power current to flow
to ground.
4. Always ready to perform.
5. Performance such that no system
disturbances are introduced by its
operation.
6. Economically feasible

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OVERHEAD GROUND WIRE

 This is a wire, generally of steel, supported

from the top of transmission-line towers
and solidly grounded at each tower.
 It is considered a preventive device, but
it does not entirely prevent the formation
of travelling waves on a line.
 Furthermore, those lines which are not
equipped with ground wires will be
subjected to disturbances which
produce surges that must be allowed to
escaped to ground

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Relays

 Various types of relays used are

o Buchloz Relay
o Over Current Relay
o Earth Fault Relay
o Over Voltage Relay
o Differential Relay
o Bus Bar Relay

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Buchloz relay
 Used for protection of oil immersed
transformers, reactors, etc.
 Phenomenon of liberation of gas in case of
fault generation is used to provide protection.
 Falling level of oil could be detected.

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Over current relay

 Protection from overload.

 Protection devices like fuse or
circuit breaker fitted with overload
coils or series connected trip coils
are used for over current
protection.

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Earth fault relay

 The earth-fault relay is designed to be used

for selective earth-fault protection, either
primary or back-up protection, in solidly
earthed or low-resistance earthed power
systems.
 When an earth-fault occurs, the relay delivers
an alarm signal, trips the circuit breaker
provide alarms, record fault data, etc., in
accordance with the application and the
configured relay functions.

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Over/under voltage relay

 Relay is used for over voltage

protection and supervision in
distribution systems.
 Relay is also used for over / under
voltage protection of generators,
Motors and Transformers.
 They are generally used for
incoming line protection.

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Differential relay

 Operates when the vector

difference of two or more
quantities exceeds a
predetermined value.
 The relay has ratio matching taps
and incorporates a second
harmonic restraint function where
large transformer magnetizing in
rush is present.

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Bus bar relay

 The scheme of busbar protection, states that

total electric current entering an electrical node
is exactly equal to total current leaving the
node.
 But this scheme has also a main disadvantage.
This scheme of protection can not discriminate
the faulty section of the busbar.
 Very short tripping time (<15 ms)
 Extreme stability against external fault,
 Short saturation-free time (≥2ms)

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Other dept. of substation
• CONTROL ROOM
• POWER LINE CARRIER COMMUNICATION ROOM
• BATTERY ROOM

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Control room

 Contain meters, control switches and

recorders located in the control building
 Used to control the substation equipment to
send power from one circuit to another or
to open or to shut down circuits when
needed.
 Annunciator is present which consist of
sounding alarm and an indicator which
indicate nature of fault and zone where
fault occurred.

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Power line carrier communication
room
 Used in case of large
interconnected system where
control leads dispatch station has
to co-ordinate the working of
various unit to see that the system
is maintained
 most economic and reliable
method of communication in
power network

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Battery room

 Batteries used are lead acid type

having solution of sulfuric and
distilled.
 Room is kept maintainable so it is
nota ccumulated with acid
vapours to avoid risk of explosion.
 Batteries are kept at healthy state
at 2.1/2.2 V/cell.

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