| 摘要 |
PURPOSE:To prevent generation of an arc by correcting the disorder of a waveform when a bypass electromagnetic contactor is opened by a semiconductor element, and opening an AC circuit at the time of a zero-cross. CONSTITUTION:An incoming line switch for an underground power distribution line for switching an existing aerial power line to an underground power line is connected between first, second power supplies and a load via temporary cables 11, 12, 13. A bypass electromagnetic contactor 4, the gate signal of a semiconductor element 5, a standby electromagnetic contactor 9 and the gate signal of a semiconductor element 8 are all opened. Coincidence of detected phases, phase interruption and phase rotation is confirmed by a detector 21, and the contactor 4 is closed. Then, an incoming line from the first power supply is closed and the contactor 4 is opened, and an electromagnetic contactor 7 is closed. Thus, switching is made to the second power supply. |
