| 摘要 |
PURPOSE:To discriminate inverse power transmission and outbreak of short- circuit accident from inverse power stop and outbreak of ground-fault accident by placing a directional relay with minor power on the secondary side of a transformer, tripping a breaker on the secondary side of the transformer, and at the same time, making operation and non-operation of an overcurrent relay placed on the primary side of the transformer. CONSTITUTION:When a breaker 1A for distribution of a power company is opened, a transformer 10 is excited reversely by a non-utility generator power, and transmission lines of the power company is reversely pressurized. At this time, the reverse excitation current from the secondary side of the transformer 10 is detected by a power directional relay 11 with minor power, and a breaker 1B for receiving power is tripped. Accordingly, the reverse pressurization of transmission lines on the company side can be prevented. When a ground-fault accident occurs in transmission lines on the company side, it is detected by a ground-fault overcurrent relay 3A for distribution of the power company, and the breaker 1A for distribution is tripped. The same as in the above- mentioned case, it in enough to use the power directional relay 11 with minor power for the detection, and trip the breaker 1B or 1C. |
