Contents | Introduction | Symbols Legend | Scheme Book

Interlock Application - Prevent Paralleling of Lines

Scheme # 22
To prevent paralleling incoming primary sources, lines 1 and 2, through primary tie bus disconnect. To prevent operation (open or closed) of the disconnects under load. Permits one power source to supply both loads through tie bus.

Under normal conditions breakers A and B are closed, disconnects C and D are lock closed, and tie bus disconnect T is locked open. Keys A-1 are held in L-O interlock on breaker A and L-C interlock on tie bus disconnect T. Keys A-2 are held in L-O interlock on disconnects C and D. Keys A-3 are held in L-O interlock on breaker B and L-C interlock on tie bus disconnect T. Keys A-4 (free keys) are shown in removable position in the L-C interlocks on disconnects C and D.

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

Reverse sequence to restore load No. 1 to line 1. To transfer load No. 2 from line 2 to line 1 through bus tie disconnect T, proceed in a similar manner.

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