| 摘要 |
<P>PROBLEM TO BE SOLVED: To obtain a low-cost three-phase overcurrent protective relay having a superior noise resistance by measuring a current in two auxiliary CT systems. <P>SOLUTION: The three-phase overcurrent protective relay includes auxiliary CTs 2a, 2b for measuring current of a main circuit, a detection circuit 4 where an output of the auxiliary CTs 2a, 2b is input and a current value of the main circuit is detected, and a CPU 7 where an output of the detection circuit 4 is input via an A/D converter 5 and a multiplexer 6 and a protection operation is executed. The auxiliary CTs 2a, 2b are for two phases, and for the remaining phase, the outputs of the respective auxiliary CTs 2a, 2b are branched and input into an addition circuit 10 composed of hardware to generate signals. <P>COPYRIGHT: (C)2011,JPO&INPIT |
