| 摘要 |
PROBLEM TO BE SOLVED: To monitor soundness of an analog input channel with a simple configuration without multiplexing an input channel, relating to a protection relay which is applied to an AC feeding circuit.SOLUTION: A protection relay includes a transformer Tr for voltage-transforming an AC power source voltage, an input channel in which an AC voltage available from one winding end of a secondary winding of the transformer is connected to a trolley line T, and an AC voltage available from the other winding end is connected to a feeder wire F, which are then transferred to a protection relay Ry that, with an AC feeder circuit that supplies a voltage available from a middle point of the secondary winding to a rail as a target of protection, detects a current flowing the trolley line and a current flowing the feeder line respectively to protect the AC feeder circuit, and an input channel monitoring device which monitors a current flowing respective input channels. The input channel monitoring circuit calculates a difference between received currents and compares a difference with a predetermined value, for detecting abnormality of an input channel. |
