| 摘要 |
PURPOSE:To certainly work a relay at the time of an internal accident and prevent error interruption from being generated at the time of a poor condition by using the relay working only at the time of the generation of the accident. CONSTITUTION:When the secondary side of a current transformer 4b is disconnected in a state that load current flows, then current i1 flows into a ratio differential relay 5, and the relay 5 is worked. In the meantime, in variation detecting element 8-1 on an increasing side, current I1 is not changed, and so the element 8-1 is not worked. Besides, in a variation detecting element 8-2 on the increasing side, current I2 is changed by IX on a reducing side, and so the element 8-2 is not worked. Accordingly, an AND circuit is not materialized, and trip command T is not generated, and so unnecessary working is prevented from being generated. In case of an internal accident, current is increased, and so either variation detecting element 8-1 or 8-2 on the increasing side is worked. Accordingly, the output of the ratio differential relay 5 is worked, and either variation detecting element 8-1 or 8-2 on the increasing side is worked, and so the output T of the AND circuit 10 is generated, and tripping can be performed. Accordingly, on internal and external accidents, a normal reaction is performed, and even if the poor condition of disconnection or the like is generated, unnecessary interruption can be prevented from being generated. |
