Patent ID: 7259947

Claim:
A phase control switching device comprising: a transforming unit having multiple phases and connected to a power system; a breaker, having multiple phases and connecting the transforming unit to the power system, each phase of the breaker being opened to break a failure current and a load current of the transforming unit and closed to excite the transforming unit; a voltage measuring unit for measuring the voltages of each phase of the breaker at a transforming unit side and at a power system side of the breaker; and a phase control switching operation processor for carrying out switching of each phase of the breaker in consideration of residual magnetic flux of the transforming unit, wherein when each phase of the breaker receives an opening instruction, the phase control switching operation processor estimates a periodic voltage zero point of a first phase from the phase of a voltage waveform measured for each phase by the voltage measuring unit and opens each contact terminal of the breaker near the voltage zero point of the first phase, at the same time with respect to all phases, and, when each phase of the breaker receives a closing instruction, the phase control switching operation processor estimates a periodic voltage zero point of the first phase from the phase of the voltage waveform of the first phase measured by the voltage measuring unit, sets the first phase opened at the voltage zero point as a first throwing phase, throws the first phase at a throwing point at which exciting incoming current at the throwing is substantially a minimum, considering the residual magnetic flux of the transforming unit, and throws other phases near the voltage zero point of the first phase, after the throwing point of the first phase.