| 摘要 |
PURPOSE:To switch a system at a phase unit by adding squared values of three phase reference sine waves of different phases to squared values of phase voltages, detecting voltage drops of phases from magnitudes of added results, and closing a changeover switch of the phases. CONSTITUTION:The system switching device comprises a three-phase reference sine wave generator 23 for obtaining a constant-voltage three-phase sine wave signal in synchronization with each phase voltage or a line-to-line voltage of a zone to be switched of a power system. The device further comprises first squaring circuits 21a-21c for squaring three-phase sine wave signals, and second squaring circuits 24a-24c for squaring line-to-line voltages or phase voltages. Squared values of the three-phase reference sine waves of different phases are added to the squared values of the phase voltages, voltage drops of the phases are detected from magnitudes of the added results, and a system changeover switch of the detected phase is controlled to be closed. Thus, a system switching of a phase unit due to a voltage drop of the phase or line-to-line unit can be conducted. |
