| 摘要 |
PROBLEM TO BE SOLVED: To make it possible to lock a differential current relay device with a countermeasure for branch loads on occurrence of monitor failure in a system having no branch terminal, by invalidating a locking command circuit by the selection of a distance relay provided as a countermeasure for branch loads of a power transmission line in a circuit in which the use of the distance relay is selected. SOLUTION: A distance relay 12 is not used when a protection relay device is applied to a system having no branch load terminal so that a distance relay nonuse condition is outputted from a distance relay nonuse condition detecting circuit 13. If the monitoring of a differential current fails, the detection signals of the differential current monitoring failure are outputted from a detector 14. Then, an AND circuit 17 is opened to output the detection signals of the differential current monitoring failure and to lock the device, specifically automatic monitoring is effected by the protection relay device. Conversely, when the device is applied to a system having a branch load terminal, the distance relay 12 is used so that its nonuse condition is not outputted from the detecting circuit 13. This causes the failure of the differential current monitoring. The AND circuit 17 is closed even if the failure detection signals are outputted from the detection circuit 14, thereby canceling the monitoring. |
