ERRONEOUS OPERATION PREVENTING DEVICE FOR MAIN AND STANDBY POWER RECEIVING LOOP SWITCHING

PURPOSE:To prevent a service interruption accident by an erroneous operation by providing normal and standby breakers for normal and standby power receiving circuits, normal and standby relays for detecting their accident currents, an auxiliary relay for locking the operation of the standby relay and auxiliary contact on a circuit for excluding the tripping of the normal breaker. CONSTITUTION:In general, breakers 12, 23 for main and standby line power receiving circuits are mutually interlocked, and only either one of the breakers can be made. At the time of loop switching, a change-over switch 43 of receiving interlock use-exclusion is changed on exlude side, the breaker can be made regardless of the state of the opposite breaker. At this time, the time limit elements 11a of excessive current relays 11, 21 and tripping by ground excessive current relays 12, 22 are locked by the switch 43. A keep relay 30 locks the operation of the relays 21, 22, and an auxiliary contact 30b is inserted to the trip circuit 15 of the breaker 13 and excludes the tripping. Thus, a service interruption accident by an erroneous operation at the time of loop switching can be prevented.