DIGITAL PROTECTION RELAY

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PROBLEM TO BE SOLVED : To add a diagnosis function, which allows sure execution of operation of a switch that is opened/closed at rare frequencies, to a digital protection relay. SOLUTION : The digital protection relay includes an analog detection circuit 4 for detecting an electrical amount of a main circuit 1 of a power system, a central processor 6, which operates output contacts 10, 11, opening/closing the switch connected to the main circuit 1, so as to measure elapsed time from the time when the switch is opened/closed until the time when the switch is opened/closed next time while monitoring an electrical amount outputted from the analog detection circuit 4, an alarm output contact 14 operated with a signal outputted from the central processor 6, and a storage device 7 that stores data of cured state of grease, used for an operation mechanism of the switch, due to its secular changes. The digital protection relay diagnoses the cured state of the grease on the basis of the elapsed time. COPYRIGHT : (C)2008, JPO&INPIT