| 摘要 |
PURPOSE:To prevent malfunction by providing overcurrent detectors to the secondary circuit of a defferentially connected current transformer and to the secondary circuit of another current transformer provided to the same power line respectively and by issuing an interruption immobility command when both current detectors and a percentage differential relay are actuated. CONSTITUTION:When an internal fault is caused to a transformer 1TR, a percentage differential relay 87 is actuated and a circuit breaker CB1 trip signal is issued. If CB1 did not trip, the current will flow to the secondary side of CT1 and CT3 and overcurrent relays 51F1 and 51F2 are actuated. As the percentage differential relay 87 and two overcurrent relays are actuated, trip signals are issued to circuit breakers CB3 and CB4. In case the secondary side of a current transformer CT1 is earthed, no trip signals will be issued to the breakers CB3 and CB4 as the overcurrent relay 51F2 is not actuated. |
