| 摘要 |
PROBLEM TO BE SOLVED: To shorten controlling time of a breaker and reduce its influence on a power system, by forming a counter which prevents unnecessary reset of a counter value even if a relay or an outside inputting condition is disconnected instantaneously. SOLUTION: A counter controller 112 for a fail safe relay and a counter controller 113 for a main detection relay are added to a digital protective relay 101. In case of an internal failure (system failure generated in a protective range of the digital protective relay 101), the input signals of respective counters become ON with the fail safe relay operated, the main relay operated, and the external condition closed,. And the counter controllers 112, 113 count up counters 108, 109. If the operation of the respective relays and the external ON condition are continued, the counter 108, 109 exceed their threshold values and an output signal becomes ON, therefore, the contact points FDX 105 and MX 106 become ON, and controlling current flows through a tripping circuit 104, thus it is possible to eliminate system failure with a breaker tripped. |
