11-Busbar Protection Busbar Protection Rf

5/26/2018 11-Busbar Protection Busbar Protection Rf

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05/02/031

Busbar Protection

Protection & Contrle / Application

Rev. A JM, September 2004


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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


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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 or

Time Delayed Distance Protection

Drawbacks


4/6308/0205/02/034 4

With Busbar Protection

BUSBARZONE

F1

Fast clearance by breakers at the busbars


5/6308/0205/02/035 5


BUSBARZONE

F2F1

Where busbars are sectionalised,

Protection can limit the amount of systemdisruption for a busbar fault


6/6308/0205/02/036 6

21 21

87BB

87BB

1/2


SS1

SS2

SS3


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21 21

87BB

87BB

2/2



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21 21 21

21 21

1/2

With NoBusbar Protection


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21 21

2/2

21

21 21

With NoBusbar Protection


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21 21 21

21 21

21 21

87BB

87BB

With Busbar protection

With NoBusbar protection


11/6308/0205/02/0311 11

Busbar Faults Are Usually Permanent

Causes of Busbar Faults :

Falling debris

Insulation failures

Circuit breaker failures

Current transformer failures Isolators switchs operated on load or outside their ratings

Safety earths left connected

Therefore :

Circuit breakers should be tripped and locked out by busbar

protection


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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


13/6308/0205/02/0313 13

Methods of Providing Busbar Protection

Frame to Earth (Leakage) Protection

Blocking Scheme Protection

Differential Protection : High Impedance

Low Impedance

Insulation

>I

>I >I >I >I>I


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Frame Leakage Protection




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Insulation

>I

Frame Leakage Busbar Protection


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>I



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>I



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>I


>I


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Can detect only earth faults

Switchgear must be insulated from earth (by standing onconcrete plinth)

Only one single earth conductor allowed on switchgear

All cable glands must be insulated

Switchgear sections must be insulated



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>I

>I


Neutral Check

False Operationbecause inducedloop

No operationprevents from

false trip


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>I

>I


Neutral Check


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>I

>I

Neutral Check



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Blocking Scheme Protection




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>I >I >I >I>I

Blocking Scheme Busbar Protection


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>I >I >I >I>I



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>I >I >I >I>I



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High Impedance Protection




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Single Bus Substation



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P1

P2

S1

S2

P1

P2

S1

S2

P1

P2

S1

S2



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Double Bus Substation

Isolator Auxiliary Switches


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yCurrent 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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yCurrent switching

Bus A

Bus B

ab

Current



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yCurrent switching

Bus A

Bus B

ab

Current



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Current switching

Bus A

Bus B

ab

Current



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Current switching

Bus A

Bus B

ab

Current



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Current switching

Bus A

Bus B

ab

Current



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Bus A

Current

Bus B

ab

Tripping switching

Tripping ab


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Main CT must be identical

Current switching via auxilliary relay is not acceptable.

Requirement of number of position contact (Disconnectorswitch) is high

Interposing CT are not acceptable

Isolator Auxiliary SwitchesC t it hi


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Current switching

Bus A

Bus B

abCurrent

Isolator Auxiliary SwitchesC t it hi


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Current switching

Bus A

Bus B

abCurrent

Bus A

Bus B

abCurrent

Isolator Auxiliary SwitchesO L d T f


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Bus A

Bus B

a

bCurrent

On Load Transfer

Isolator Auxiliary SwitchesOn Load Transfer


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Bus A

Bus B

abCurrent

On Load Transfer



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Bus A

Bus B

abCurrent

On Load Transfer



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Bus A

Bus B

abCurrent

On Load Transfer



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Bus A

Bus B

ab

Current

On Load Transfer



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Bus A

Bus B

abCurrent

On Load Transfer



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Bus A

Bus B

abCurrent

On Load Transfer

Isolator Auxiliary SwitchesCheck Zone


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Bus A

Bus B

TripBusA

TripBusB

Zone A

Zone B

Check Zone



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Bus A

Bus B

TripBusA

TripBusB

Zone A

Zone B

Check Zone

Current

switching

failure

False

Tripping



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Bus A

Bus B

TripBusA

TripBusB

Check

Zone

Zone A

Zone B

Check Zone



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Bus A

Bus B

TripBusA

TripBusB

Zone A

Zone B

Check Zone



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Bus A

Bus B

TripBusA

TripBusB

Check

Zone


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One Breaker and a HalfSubstation


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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

11-Busbar Protection Busbar Protection Rf

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