| 摘要 |
PROBLEM TO BE SOLVED: To prevent unnecessary operations of a differential relay in case of an external accident. SOLUTION: An overvoltage(OV) discriminating and calculating part 20, requiring immediate operation for a change in system voltage, with respect to an external trouble occurrence at a system power supply end, in a state with exciting rush current is flowing, conducts quicker operation and returns quicker than a differential factor. The output of the overvoltage(OV) discriminating and calculating part 20 is turned OFF, and the output of a return delay timer 24 controlled by the output of a differential discriminating and calculating part 16 is turned OFF after T2 hours. Through the return delay timer 24, the differential discriminating and calculating part 16 returns, the return delay timer 24 is reset (returned), and return cooperation with the differential factor is made positively, and reliability is improved. |
