11

Presentation on

SUB STATION BASIC : PART – I Single Line Diagram

Bus Bar Arrangement

Sub Station Layout

22

Introduction

The economics of generation of electrical energy and the huge demands for power in the modern times requires creation of bigger POWER STATIONS.

The power stations may be far from the load centre / consumers and so long high voltage transmission lines are necessary for transfer of bulk power from power station to different load centres.

In between power station and ultimate consumers a number of transformation and switching stations are to be created. Such stations are known as Sub Station.

33

Concept of Power System

44

What is Sub Station ?

A SUBSTATION is a subsidiary station of an electricity Generation, Transmission and Distribution system where voltage is transformed from high to low or vise versa using transformers. Electric power may flow through several substations between generating plant and consumer, and may be changed in voltage in several steps. A Step-up transformer increases the voltage and proportionally decreases the current, while a step-down transformer decreases the voltage and proportionally increases the current for domestic and commercial distribution.

55

House Electrification

DISTRIBUTION BOARD

3- & 1- MCBsBUS BAR STRIPS

SOURCE CABLE (Incoming)

3- LOAD CABLE (Outgoing)

1- LOAD CABLE (Outgoing)

1- LOAD CABLE (Outgoing)

1- LOAD CABLE (Outgoing)

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General Arrangement

LIGHTNING ARRESTOR

POTENTIAL TRANSFORMER

TR. LINE (INCOMER / OUTGOING)

TR. LINE (INCOMER)

CURRENT TRANSFORMER

WAVE TRAP

EARTH SWITCH

ISOLATOR

CIRCUIT BREAKER

ISOLATOR

CAP. VOLTAGE TRANSFORMER POWER TRANSFORMER

SUB STATION

BUS BAR

77

Single Bus Bar Scheme

BUS BAR

SUB STATION POWER STATION LOAD CENTRE

Faulty

Faulty

88

Advantage & Disadvantage

SINGLE BUS BAR (UPTO 33kV SS)

Advantages

Lowest cost

Small land area required

Easily expandable

Simple in concept and operation

Disadvantages

Lowest reliability

Failure of a circuit breaker causes loss of the feeder

Bus fault causes loss of the entire substation

99

Improvement

Main Disadvantage ?

Loss of the entire Sub Station in case of Bus fault.

Requirement ?

Avoid loss of entire bus i.e., entire Sub Station in Bus fault.

How to Achieve ?

By Sectionalizing the Single Bus Bar.

Arrangement ?

Sectionalisation of Single Bus Bar Arrangement.

1010

Sectionalization of Single Bus Bar Scheme

BUS SECTION - I BUS SECTION - II

SUB STATION POWER STATION LOAD CENTRE

Faulty

Faulty

SECTIONALIZING CB

1111

Advantage & Disadvantage

SECTIONALIZATION BUS BAR (33kV & 66kV SS)

Advantages

Flexible operation

Higher reliability than single bus scheme

Isolation of bus sections for maintenance

Loss of only part of the substation for a bus fault

Disadvantages

Loss of circuit for breaker failure

A sectionalized bus arrangement has a higher cost than a single bus scheme as additional circuit breaker and isolators are required for sectionalizing

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Improvement

Main Disadvantage ?

Circuit Breaker failures are more than Bus fault. Thus, we loose important feeder in case of Circuit Breaker outage.

Requirement ?

Avoid loss of important circuit in case of Circuit Breaker outage.

How to Achieve ?

By by-passing the faulty circuit breaker.

Arrangement ?

Main and Transfer Bus Bar Arrangement.

1313

Main and Transfer Bus Bar Scheme

MAIN BUS I

SUB STATION POWER STATION

TRANSFER BUS

LOAD CENTRE

Faulty

Faulty

TRANSFER BUS COUPLER (TBC)

1414

Advantage & Disadvantage

MAIN & TRANSFER BUS BAR (132kV SS)

Advantages

Circuit breaker outage / maintenance does not disrupt the service of feeder / circuit

Reasonable in cost

Fairly small land area

Easily expandable

Disadvantages

Bus Fault causes disruption of service of entire sub station

An additional circuit breaker is required for bus tie

1515

Improvement Main Disadvantage ?

Bus fault in a sub station having more nos. of circuits causes greater interruption of power. In Main and Transfer Bus Bar arrangement bus fault results loss of entire sub station i.e., all circuits.

Requirement ?

Avoid loss of too many circuits in case of bus fault.

How to Achieve ?

By providing another Main Bus for connection of circuits.

Arrangement ?

Double Main Bus Bar Arrangement.

1616

Double Main Bus Bar Scheme

MAIN BUS I

MAIN BUS II

SUB STATION POWER STATION LOAD CENTRE

Faulty

Faulty

BUS COUPLER (BC)INTERRUPTION

Single Bus Scheme Mode

1717

Advantage & Disadvantage

DOUBLE MAIN BUS BAR (220kV SS)

Advantages

Bus Bar outage / maintenance does not disrupt the service of any feeder / circuit

Reasonable in cost

Fairly small land area

Easily expandable

Disadvantages

Circuit Breaker outage causes disruption of service of that feeder

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Improvement Main Disadvantage ?

Double Main Bus arrangement is an alternative to Main & Transfer Bus scheme. In both cases, the investment is same. The only difference is that in Double Main Bus the outage of Bus Bar and in Main & Transfer Bus the outage of Breaker is prioritized.

Interruption of Power during Isolator operation.

Requirement ?

Both Bus fault and Circuit Breaker outage are to be taken care off.

How to Achieve ?

By using one of the Main Buses as “Main Cum Transfer Bus”.

Arrangement ?

Double Main Cum Transfer Bus Bar Arrangement.

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Double Main Cum Transfer Bus Bar Scheme

BUS I CUM TRANSFER

BUS II

SUB STATION POWER STATION LOAD CENTRE

Faulty

Faulty

BC

INTERRUPTION

Single Bus Scheme Mode

Main and Transfer Bus Scheme Mode

2020

Advantage & Disadvantage DOUBLE MAIN CUM TRANSFER BUS BAR (220kV

SS)

Advantages

Bus Bar outage / maintenance does not disrupt the service of any feeder / circuit

Circuit Breaker outage does not cause disruption of service of that feeder

Reasonable in cost

Fairly small land area

Easily expandable

Disadvantages

Additional Isolator in each circuit increases the cost

2121

Improvement

Main Disadvantage ? Double Main Cum Transfer Bus Bar

arrangement outage of Circuit Breaker and Bus together causes loss of faulty Circuit Breaker feeder.

Interruption of Power during Isolator Operation.

Requirement ? Avoid loss of feeder in case of simultaneous

outage of Circuit Breaker and a Main Bus.

How to Achieve ? By providing separate transfer Bus along with

Double Main Buses.

Arrangement ? Double Main and Transfer Bus Bar

Arrangement.

2222

Double Main and Transfer Bus Bar Scheme

SUB STATION POWER STATION LOAD CENTRE

BUS I

BUS II

TRANSFER BUS

Faulty

Faulty

BC

TBC

INTERRUPTION

Single Bus Scheme Mode

Main and Transfer Scheme Mode

2323

Advantage & Disadvantage

DOUBLE MAIN AND TRANSFER BUS BAR (220kV SS)

Advantages

Bus Bar outage / maintenance does not disrupt the service of any feeder / circuit

Circuit Breaker outage does not cause disruption of service of that feeder

Maintenance of Bus and CB does not interrupt supply

Disadvantages

Additional Isolator and Circuit Breaker required for transfer Bus tie.

2424

Improvement Main Disadvantage ?

Interruption of Power during Isolator operation.

Interruption of Power is likely to cause major disturbance if the feeders are important and heavily loaded.

Requirement ?

Avoid interruption of important and heavily loaded feeders during bus fault or outage of Circuit Breaker.

How to Achieve ?

By connection of circuits for double feed through Circuit Breakers and avoid Isolator switching.

Arrangement ?

One and a Half Breaker Bus Bar Arrangement.

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One and a Half Breaker Bus Bar Scheme

BUS I BUS II

MAIN CB MAIN CBTIE CB

MAIN CB MAIN CBTIE CB

SUB STATION

POWER STATION

LOAD CENTRE

Faulty

Faulty

Faulty

Faulty

2626

Advantage & Disadvantage ONE & HALF BREAKER BUS BAR (400kV SS)Advantages Flexible operation High reliability Can isolate either main bus for maintenance

without disrupting service Can isolate any circuit breaker for

maintenance without disrupting service Double feed to each circuit Bus fault does not interrupt service to any

circuits All switching done with circuit breakersDisadvantages One-and-a-half breakers are required per

circuit

2727

Improvement Important

In transmission system the highest reliable Bus Bar Arrangement adopted by POWERGRID is One and a Half Bus Bar Scheme. However, where bulk power evacuation without alternative path is concerned, further reliable arrangement may be adopted.

What Arrangement ?

Connection of circuits in Double Bus Bar Arrangement where each circuit will have a spare Circuit Breaker in service.

Where can be used ?

In large Generating Plants where implication of generation outage is much higher than the cost of Circuit Breakers.

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Double Breaker Bus Bar SchemeBUS I BUS II

SUB STATION

POWER STATION

LOAD CENTRE

Faulty

Faulty

2929

Advantage & Disadvantage DOUBLE BREAKER BUS BAR (Mega Generating

Units)Advantages Flexible operation Very high reliability Isolation of either main bus for maintenance

without disrupting service Isolation of any circuit breaker for

maintenance without disrupting service Double feed to each circuit No interruption of service to any circuits from

bus fault Loss of only one circuit for breaker failure All switching with circuit breakersDisadvantages This configuration carries a high cost Two circuit breakers are required for each

circuit.

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PHOTOGRAPHS

3131

Photographs

BUS BAR

3232

CIRCUIT BREAKER ISOLATOR AND EARTH SWITCH

Photographs

3333

CURRENT TRANSFORMER POTENTIAL TRANSFORMER

Photographs

3434

LIGHTNING ARRESTERCAPACITOR VOLTAGE

TRANSFORMER

Photographs

3535

WAVE TRAP TRANSMISSION LINE

Photographs

3636

TRANSFORMER

Photographs

3737

REACTOR

Photographs

3838

Photographs

SUB STATION

3939

LAYOUT & SECTION

4040

DRAWING – EXAMPLE : 1

CL-CT

CL-WT

CL-CVTCL-LA

A

A

B

B

CL-ISO

CL-CB

CL-ISO

SINGLE LINE DIAGRAM

CL-LA

CL-TFR.

SLIDE : 1 of 3

LAYOUT DRAWING

4141

Ground LevelLA CVT WT CT ISO & ES CB ISO

SECTION - AA

DRAWING – EXAMPLE : 1

SLIDE : 2 of 3

Earth Wire

Gantry

4242

Ground LevelLA CT ISO CB ISO

SECTION - BB

DRAWING – EXAMPLE : 1

SLIDE : 3 of 3

Transformer

4343

DRAWING – EXAMPLE : 2

SLIDE : 1 of 3

CL-CTCL-WTCL-CVTCL-LA

A

A

B

B

CL-ISO

CL-CB

CL-ISO

CL-LA

CL-TFR.

CL-ISO

SINGLE LINE DIAGRAM

LAYOUT DRAWING

4444

SECTION - AA

DRAWING – EXAMPLE : 2

SLIDE : 2 of 3

Ground LevelLA CVT WT CT ISO & ES CB ISO ISO

Gantry

Earth Wire

4545

SECTION - BB

DRAWING – EXAMPLE : 2

SLIDE : 3 of 3

Ground LevelCT ISO & ES CB ISO ISO

Gantry

LATransformer

Earth Wire

4646

4747

QUESTION

What are the different parts of Power System ?

What is Sub Station ?

What is Single Line Diagram ?

Explain BUS BAR ?

What do you understand by Bus Bar Arrangement ?

What are the limitations of Single Bus Bar Scheme ?

What is the advantage of Sectionalisation of Single Bus Bar over Single Bus Arrangement ?

Bus Bar Arrangement for 132kV Sub Station is .

4848

QUESTION

What are the limitations of Main & Transfer Bus Bar Scheme ?

How does Double Main Bus Scheme differ from Main & Transfer Bus Arrangement ?

What is the difference between Double Main Bus and Double Main Cum Transfer Bus Arrangement ?

What is the Bus Bar Arrangement for Sub Station having voltage class 400kV & above ?

What is the advantages of One and a half Breaker Bus Bar Scheme ?

What is the advantage & Disadvantage of Two Breaker Bus Bar Scheme and where the same is used ?

4949

QUESTION

Explain the purpose of using

(a) Circuit Breaker

(b) Isolator

(c) Earth Switch

(d) Lightning Arrestor

(e) Current Transformer

(f) Potential Transformer

(g) Capacitor Voltage Transformer

(h) Wave Trap

(i) Power Transformer

5050