PROTECTIVE RELAY

PROBLEM TO BE SOLVED: To reduce time of the performance test for a protective relay, and the cost of testing facilities. SOLUTION: The analog signal level-converted by an input transformer group 1 is converted into a digital signal by a sample-and-hold circuit 3, a multiplexer 4, and an A/D converter 5 and stored into a memory 6 as voltage power data, after the high frequency element thereof is removed by an analog filter 2. A CPU 7 transfers the voltage power data stored in the FIFO memory 6 to a RAM 8. The CPU 7 compares a setting value read from a setting value memory 10 with the result computed from the input signal of an electric power system and determines a relay action. The CPU 7 is connected to a test circuit 11, provides various status signals indicating the working condition of the protective relay for the test circuit 11, the test circuit 11 starts processing according to a test switch on signal by a test switch (not shown), and provides the prescribed test signal for one analog filter 2.