Interlock Application Scheme # 8 - Isolating Switches and Breaker

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Interlock Application - Isolating Switches and Breaker

Scheme # 8
To prevent operation of disconnects A and B when breaker C is closed. To permit servicing of breaker when disconnects are locked open.

Breaker C and disconnects A and B are shown closed. One key A-1 is held in breaker L-O interlock and the other key A-1 is held in L-O interlock on disconnect B. Key A-2 is held in L-O interlock on disconnect A.

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9.

Open breaker.
Turn key A-1 in L-O interlock on breaker to lock open. Key A-1 is now free.
Insert key A-1 in L-C interlock on disconnect A and turn to unlock. Key A-1 is now held.
Open disconnect A.
Turn key A-2 in L-O interlock on disconnect A to lock open. Key A-2 is now free.
Insert key A-2 in L-C interlock on disconnect B and turn to unlock. Key A-2 is now held.
Open disconnect B.
Turn key A-1 in L-O interlock on disconnect B to lock open. Key A-1 is now free.
Insert key A-1 in breaker L-O interlock and turn to unlock for operation during servicing.

Reverse sequence to restore service.

Links for more interlock application scheme information:

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Scheme # 1
Scheme # 2
Scheme # 3
Scheme # 4
Scheme # 5
Scheme # 6
Scheme # 7
Scheme # 8
Scheme # 9
Scheme # 10
Scheme # 10A
Scheme # 11 Scheme # 12

Scheme # 13
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Scheme # 17A Scheme # 18
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Scheme # 22 Scheme # 23
Scheme # 24

Scheme # 25
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Scheme # 27 Scheme # 28
Scheme # 29
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Scheme # 33 Scheme # 34
Scheme # 35
Scheme # 35A
Scheme # 36

Scheme # 37
Scheme # 38 Scheme # 39
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Scheme # 42A
Scheme # 42B
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Scheme # 43A
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Scheme # 45
Scheme # 45A