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Interlock Application - Prevent Paralleling of Lines

Scheme # 21
To prevent paralleling three power sources through a common tie bus not normally in service. To permit feeding any load bus from a second power source through the tie bus only when authorized by supervisor. To permit one power source to supply all three load busses through the tie bus only when authorized by supervisor.

Breakers A, B, and C are normally closed. Breakers D, E, and F are normally open. Under normal conditions key A-1 is held in breaker A interlock, key A-2 is held in breaker B interlock, and key A-3 is held in breaker C interlock. Key A-5 is retained by supervisor.

To transfer load from line No. 1 to line No. 2 or line No. 3 through tie bus, proceed as follows:

Reverse sequence to restore load to line No. 1.

To transfer load from lines No. 1 and No. 2 to line No. 3 through tie bus, proceed as follows:

Reverse sequence to restore load to lines No. 1 and No. 2.

Scheme # 25
Scheme # 26
Scheme # 27 Scheme # 28
Scheme # 29
Scheme # 30
Scheme # 31
Scheme # 32
Scheme # 33 Scheme # 34
Scheme # 35
Scheme # 35A
Scheme # 36