This scheme is used to prevent the opening of the non-load break disconnect switch while the breaker is closed; insuring the disconnect switch is locked open before the breaker can be re-closed for testing or servicing.
Initial Condition: The load is fed from Line 1 through no-load disconnect switch #1 and Breaker #1. Switch #1 is locked closed with no interlock key present in its LC position key interlock, switch #1 has a "B" key captive in its LO position key interlock. Breaker #1 is closed with its respective interlock key "A" captive.
Opening the non-load break disconnect switch and servicing/testing the breaker: Open and lock Breaker #1 thereby releasing the "A" key. Use the "A" key to unlock and open Switch #1. Lock Switch #1 in the open position thereby removing the "B". Use the "B" key to unlock and re-close Breaker #1 for servicing/testing. Reverse to restore the initial condition.
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