07-Busbar Protection Busbar Protection Rf

08/0205/02/031 105/02/031

Busbar Protection

Protection & Contrôle / Application

Rev. A JM, September 2004

08/0205/02/032 2

Without Busbar Protection

F2F1

There are fewer faults on busbars than on other parts of the power system. No risk of dislocation of system due to accidental operation of busbar protection.

Argues

08/0205/02/033 3

Without Busbar Protection

F2F1

Slow fault clearance.Busbar faults at F1 and F2 are cleared by remote time delayed protection on circuits feeding the faults:

Time Delayed Overcurrent orTime Delayed Distance Protection

Drawbacks

08/0205/02/034 4

With Busbar Protection

BUSBARZONE

F1

Fast clearance by breakers at the busbars

08/0205/02/035 5


BUSBARZONE

F2F1

Where busbars are sectionalised,Protection can limit the amount of system

disruption for a busbar fault

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21 21

87BB

87BB

1/2


SS 1

SS 2

SS 3

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21 21

87BB

87BB

2/2


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21 21 21

21 21

1/2

With No Busbar Protection

08/0205/02/039 9

21 21

2/2

21

21 21

With No Busbar Protection

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21 21 21

21 21

21 21

87BB87BB

With Busbar protection

With No Busbar protection

08/0205/02/0311 11

Busbar Faults Are Usually Permanent

Causes of Busbar Faults :

Falling debris

Insulation failuresCircuit breaker failuresCurrent transformer failuresIsolators switchs operated on load or outside their ratingsSafety earths left connected

Therefore :

Circuit breakers should be tripped and locked out by busbar protection

08/0205/02/0312 12

Busbar Protection must be :

RELIABLE– Failure to trip could cause widespread damage to the substation

STABLE– False tripping can cause widespread interruption of supplies to

customers / possible power system instability

DISCRIMINATING– Should trip the minimum number of breakers to clear the fault

FAST– To limit damage and possible power system instability

08/0205/02/0313 13

Methods of Providing Busbar ProtectionFrame to Earth (Leakage) Protection

Blocking Scheme Protection

Differential Protection : High ImpedanceLow Impedance

Insulation

>I

>I >I >I >I>I

08/0205/02/0314 1405/02/0314

Frame Leakage Protection



08/0205/02/0315 15

Insulation

>I

Frame Leakage Busbar Protection

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>I


08/0205/02/0317 17

>I


08/0205/02/0318 18

>I


>I

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Can detect only earth faults

Switchgear must be insulated from earth (by standing on concrete plinth)

Only one single earth conductor allowed on switchgear

All cable glands must be insulated

Switchgear sections must be insulated


08/0205/02/0320 20

>I

>I


Neutral Check

False Operation because induced loop

No operation prevents from false trip

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>I

>I


Neutral Check

08/0205/02/0322 22

>I

>I

Neutral Check


08/0205/02/0323 2305/02/0323

Blocking Scheme Protection



08/0205/02/0324 24

>I >I >I >I>I

Blocking Scheme Busbar Protection

08/0205/02/0325 25

>I >I >I >I>I


08/0205/02/0326 26

>I >I >I >I>I


08/0205/02/0327 2705/02/0327

High Impedance Protection



08/0205/02/0328 2808/0205/02/0328

Single Bus Substation

08/0205/02/0329 29

P1

P2

S1

S2

P1

P2

S1

S2

P1

P2

S1

S2


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08/0205/02/0331 31


08/0205/02/0332 32


08/0205/02/0333 3308/0205/02/0333

Double Bus Substation

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Isolator Auxiliary Switches Current switching

Bus A

Bus B

ab

Current

P1

P2

S1

S2

P1

P2

S1

S2

P1

P2

S1

S2

P1

P2

S1

S2

P1

P2

S1

S2

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Bus A

Bus B

ab

Current

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Bus A

Bus B

ab

Current

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Bus A

Bus B

ab

Current

08/0205/02/0338 38


Bus A

Bus B

ab

Current

08/0205/02/0339 39


Bus A

Bus B

ab

Current

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Bus A

Current

Bus B

ab

Isolator Auxiliary Switches Tripping switching

Tripping ab

08/0205/02/0341 41

Main CT must be identical

Current switching via auxilliary relay is not acceptable.

Requirement of number of position contact (Disconnector switch) is high

Interposing CT are not acceptable

08/0205/02/0342 42


Bus A

Bus B

abCurrent

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Bus A

Bus B

abCurrent

Bus A

Bus B

abCurrent

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Bus A

Bus B

abCurrent

Isolator Auxiliary Switches On Load Transfer

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Bus A

Bus B

abCurrent


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Bus A

Bus B

abCurrent


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Bus A

Bus B

abCurrent


08/0205/02/0348 48

Bus A

Bus B

ab

Current


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Bus A

Bus B

abCurrent


08/0205/02/0350 50

Bus A

Bus B

abCurrent


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Bus A

Bus B

Trip

Bus

A

Trip

Bus

B

Zone AZone B

Isolator Auxiliary Switches Check Zone

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Bus A

Bus B

Trip

Bus

A

Trip

Bus

B

Zone AZone B


Current switching failure

False Tripping

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Bus A

Bus B

Trip

Bus

A

Trip

Bus

B

Check Zone

Zone AZone B


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Bus A

Bus B

Trip

Bus

A

Trip

Bus

B

Zone AZone B


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Bus A

Bus B

Trip

Bus

A

Trip

Bus

B

Check Zone


08/0205/02/0356 5608/0205/02/0356

One Breaker and a Half Substation

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Bus A Bus B

P1

P2

S1

S2

P1

S1

P2

S2

P1P2

S1S2

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Bus A Bus B

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Bus A Bus B

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Bus A Bus B

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Bus A Bus B

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Bus A Bus B

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Bus A Bus B

P1

S1

P2

S2

P1

S1

P2

S2

P1

S1

P2

S2

P1

S1

P2

S2

07-Busbar Protection Busbar Protection Rf

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