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 by the removal of and evidence/hold-off/ breaker test key.
Initial Condition: The load is fed from line 1 through non-load break 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 evidence/hold-off 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: 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 evidence/hold-off key. Supervisory personnel may hold this key as evidence of the switching operation. Reverse to restore the initial condition.
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