400kv Substation Training report

-Shailendra YadavEE-42(0705420096)

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INTRODUCTION OF SUBSTATION

It is situated at 26°34’2’’N & 80°32’57’’E coordinates in Dahi Chowki 6.64 km far from Unnao railway station.

Constructed during 1994-98 by CGL.

The whole substation is divided in three parts:132kv switchyard400/220kv switchyard765kv switchyard (Under construction)

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INCOMING & OUTGOING LINE OF SUBSTATION

•Unnao to Lucknow (400KV & 220KV both separate)•Unnao to Bareily-1 (400KV) •Unnao to Bareily-2 (400KV)•Unnao to Agara (400KV)•Unnao to Panki Kanpur(400KV & 220KV both separate)•Unnao to Anpara (400KV)•Unnao to PGCIL Lucknow-1 (400KV)•Unnao to PGCIL Lucknow-2 (400KV)•One bus bar for 400/220KV 315MVA ICT-1 & ICT-2 line.

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OUTDOOR EQUIPMENT USED IN SUBSTATION

Two 100MVA 220/132KV transformer Two 315MVA 400/220KV transformer Shunt reactor Capacitor bank SF6 circuit breaker Isolators Lightning arresters Current transformer Capacitor voltage transformer Wave trap Isolators

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TransformerH.V. side bushing CT

COOLING SYSTEM(ONAN)

ConservaterTank

L.V. side bushing CTs

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Oil pump

Oil pump is used for circulating oil forcelly.

Radiator plates are used for increasing surface area for natural air cooling.

Radiator plates

Earthing plate

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we use Cooling fans for forced air cooling of transformer . Total six fans are used for each 100MVA and eight fans are used for each 315 MVA transformer.But all fans never start at same time . It start in pairs .

COOLING FANS

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Tertiary terminal

Tertiary terminal mostly opened.

The output voltage of tertiary terminal is 11KV in 100MVA transformer and 33KV in 315 MVA transformer

Pressure relief valve box

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OLTC chamber

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TERMINALS ON TANK COVER

In these photos we can see fogging near transformer due to operation fire protection system.

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BUCHHOLZ RELAY

Buchholz relay is a safety device mounted on some oil-filled power transformers and reactors. It is used as a protective device sensitive to the effects of dielectric failure inside the equipment.

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OTI & WTI

OTI –oil temp. indicator measure temp. of oil filled in transformer. In OTI has two mercury bulb.

WTI- winding temp. indicator measure winding temp of transformer. It has four mercury bulb.

OTI panelWTI panel

mercury bulb

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CURRENT TRANSFORMER

In  electrical engineering, a current transformer (CT) is used for measurement of electric currents. Current transformers, together with voltage transformers (VT) (potential transformers (PT)), are known as instrument transformers. When current in a circuit is too high to directly apply to measuring instruments, a current transformer produces a reduced current accurately proportional to the current in the circuit, which can be conveniently connected to measuring and recording instruments.

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PROTECTION DIAGRAM

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.The device has at least four terminals, a high-voltage terminal a ground terminal and at least one set of secondary terminals. CVTs are typically single-phase devices

CAPACITOR VOLTAGE TRANSFORMER

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Cross sectional view of CVT

1 - Primary terminal2 - Cast aluminum bellow housing3 - Stainless steel expansion bellow4 - Compression spring5 - Insulated voltage connection6 - Capacitor elements7 - Insulator (porcelain or composite)8 - Voltage divider tap connection9 - Cast-epoxy bushing10 - HF terminal connection11 - Ferro-resonance suppression device12 - Secondary terminals13 - Oil level sight-glass14 - Aluminum terminal box15 - Intermediate transformer16 - Oil/air block17 - Oil sampling device18 - Compensating reactor19 - Aluminum cover plate

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1. High Voltage terminal2. Compensation reactor3. Intermediate voltage transformer4. Ground terminal5. Ferro-resonance suppression device6. Damping resistor7. Carrier (HF) terminal (optional)8. Overvoltage protective device9. Secondary terminals10. Link, to be opened for test purposes

PRINCIPLE CIRCUIT DIAGRAM OF CVT

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CIRCUIT BREAKER

A circuit breaker is an automatically-operated electrical switch designed to protect an electrical circuit from damage caused by overload or short circuit.In this image we can see a SF6 circuit breaker with double break system.

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ISOLATORS

An isolators switch are used to completely de-energized an electrical circuit. High-voltage isolation switches are used in electrical substations to allow isolation of apparatus such as circuit breakers and transformers, and transmission lines, for maintenance.

Isolating rod

Earth link rod

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PANTOGRAPH ISOLATORS

In open state In close state

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Central rotating double break isolator

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Wave trap

Wave trap are used in power system for carrier communication. It trap the higher frequency above 50Hz. It is the effort to utilize the same transmission line between two substation for the purpose of communications

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LIGHTNING ARRESTOR

The overvoltage protection is obtained by the use of lightning / surge arresters.Lightning Arresters or Surge Arresters are always connected in Shunt to the equipment to be protected, they provide a low impedance path for the surge current to the ground.Mostly in present days zinc oxide (ZnO) gapless arresters are in use.

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INTERPOSING C.T.

The interposing CTs are used for Power transformer Differential Protection circuit. In a delta/Star Power transformer, the cts will be connected star and delta formation, for eliminating Zero sequence current on star side. There will be mismatch of secondary current , to maintain equilibrium, interposing Cts will be connected to Delta formed CTs.

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RELAYS

Differential relay

O/F protection +FFR

Group A trip relay

CB trouble relay

Group B trip relay

DR earth switch relay

O/C protection relays

Breaker failure relay

RES E/F +O/LProtection relay

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Relay testing boxA outer view of Relay

Relay conti….

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SHUNT REACTOR

Shunt Reactor is a thyristor controlled high impedance transformer.A stable bus voltage can be maintained by providing variable reactive power based on the bus voltage deviations due to the load variations.

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SHUNT CAPACITOR BANK

Shunt capacitor banks are used to improve the quality of the electrical supply.provide capacitive reactive compensation.Power factor correction.

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