| 摘要 |
PURPOSE:To avoid an error operation of the selective breaking, by such means that, with the operation processed for the load current hourly integrated value by a current calculator, during the period with a level of said value above the predetermined value, the signal be transmitted to a voltage relay to make its locking. CONSTITUTION:A load current, flowing through a common bus 8, is detected by a current transformer 7, with the operation processed for the load current hourly differentiated value by a current calculator 9, during the period, in which its value is bigger than a predetermined level, the signal is transmitted to a voltage relay 10 to make its locking. In this way, during said period, the signal is never transmitted from the voltage relay 10 to a selective breaking device 12, 13, thus with an error operation of selective beaking made avoidable. |
