PROTECTIVE RELAY

PROBLEM TO BE SOLVED: To provide a protective relay that predicts the occurrence of failures in future. SOLUTION: The protective relay 1 inputs a current of a power feed line L2 from a current sensor 4, inputs a voltage of a power transmission system L1 from a voltage sensor 5, and transmits a block command signal to a blocker 3 when detecting an overcurrent or an overvoltage. In the protective relay 1, a processing unit 11 inputs a digital signal of a DC voltage which is converted from an AC voltage of the power transmission system L1 from an analog/digital converter A/D, inputs an output voltage of an AC from a power supply unit 15, and inputs inspection data (test current, test voltage and operation time) from a test device 2 which is connected at inspection via an external interface 14. Next, each of the input data is stored in a memory 12, and a time change of the input data is displayed on a display 13. Then, the time change of the input data is compared with the past data stored in the memory 12 and a setting value, and when it is predicted that there is a probability that the failure may occur in the protective relay 1, an alarm of the occurrence of the failure is displayed on the display 13. COPYRIGHT: (C)2011,JPO&INPIT