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STUDY OF SUBSTATION

EQUIPMENT ANDPROTECTION

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ABSTRACT:

The economics of generation of electrical

energy and the huge demands of powerin the modern times require creationbigger power plant . These may be hydro, thermal , atomic etc . The transmission

network is inevitable . large and highvoltage transmission lines are necessaryto transmit huge blocks of power fromthe source of generation to load centers .

In b/w the power plant and ultimateconsumer a number of transmission andswitching stations have to be created .This is done by SUBSTATION

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Major equipments of

Substation

Power Transformers Bus Bars

Circuit breakers

Isolators Relays

Control Panels

Instrument Transformers

DC System

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Power Transformers

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BUS BARS

The choice of the bus bars scheme for

a substation depends upon the degree

of reliability and economic justification.The degree of reliability is evaluated

by determining the continuity of

service and possible faults.TYPES OF BUS BARS

ARRANGEMENTS:

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ARRANGEMENT

SSSSSSSSI

This system is used for 132 KV

substations. It is cheapestamong all the others bus bars. It

is totally shut down in case of a

fault.

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DOUBLE BUS BARS: This system is costlier then a single bus bars

system. One bus can serve as reserve, which is

used during maintenance or fault. It is used for 220

KV sub stations.

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CIRCUIT BREAKERS

Circuit breaker is automatic switching device which can

carrying normal current and switching in & out normalloads

Interrupt short circuiting currents

Able to performer auto reclose duty. Classification of Circuit breaker:

Based on VOLTAGE

Low-less than 1kv

Medium-1kv to 52kv

High/Extra High-66kv to 765kv

Ultra High-above 765kv

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Based on LOCATION Indoor

Outdoor

Based on INTERRUPTING MEDIUM

Air breakAir break Circuit breaker(ACB)

Air blastAir blast Circuit breaker..(ABCB)

Bulk oil.. Bulk oil Circuit breaker.(BOCB)

Minimum oil..Minimum oil Circuit breaker.(MOCB)

SF6 gas insulated.SF6 Circuit breaker

Vacuum Vacuum Circuit breaker(VCB)

Selection of a CB depends on:

Type of application Rated voltage, current

Its breaking capacity(fault level of the installation)

Auto-reclose duty cycle

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SF6 CIRCUIT BREAKER

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Opening operation: Opening is affected by pulling the insulating rod

(201), piston rod (111), puffer cylinder (110)moving contact, moving arc contact (107) andthe nozzle (105).After contacts wipe the

stationary and moving and contact (104), (107)separate, there by generating arc. During downward movement the gas in puffer chamber buildsup and high pressure gas flows through nozzleand quenches the arc.

Closing Operation: In closing operation, insulating rod (201) is pulled

up and the parts move in the reverse direction ofopening operation. And also SF6 gas taken in topuffer chamber.

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ADVANTAGES OF SF6 CB

Mostly widely used in EHV application

Low operating noise

Simple construction & compact size

Easy installation, inspection &

maintenance.

SF6 is identified as a green house

gas.

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POTENTIAL TRANSFORMER

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What are Relays?

Relays are electrical switches

that open or close another

circuit under certain conditions.

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Relay Purpose

Isolate controlling circuit from controlled circuit.

Control high voltage system with low voltage.

Control high current system with low current.

Logic Functions

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How a Relay Works

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How a Relay Works

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INSTRUMENT TRANSFORMERS

INSTRUMENT TRANSFORMERS: Current transformer

Potential transformer

Current transformer: Currenttransformer are used for supplying the

current circuits of indicatinginstruments (ammeters, watt metersetc) recording meters (energy metersetc) and protective relays.

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CT is ideally a short circuitedtransformer where the secondary

terminal voltage is zero, and the

magnetizing current is negligible. Ip*Np =Is*Ns

Ratio error

Phase angle error Composite error

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CURRENT TRANSFORMER

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VOLTAGE TRANSFORMER: These instrument are used for supplying the voltage

circuit of indicating instruments, meters, and protectiverelay.

All voltage transformer are designed for a standardsecondary voltage of 110v, 110/1.732 (63.5)

For voltage transformers at the following is valid:

Ep/Es=Np/Ns

Actual voltage ratio =Primary volts/secondary volts

Voltage transformer errors:

A) voltage ratio error B) Phase angle error.

The errors at which the VTs operate depend on itsburden and primary voltage

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ANY QUERIES?

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