Patent ID: 7936093

Claim:
A phase control switching device that controls a closing phase of a three-phase switching device connected between a power-supply-side transmission line and a compensation transmission line having a shunt reactor, the phase control switching device comprising: a voltage measuring unit that measures each phase voltage in the power-supply-side transmission line; a voltage-changing-ratio zero-point-period detecting unit that detects a period of zero points of each phase voltage changing ratio obtained by a time derivative of the phase voltage measured by the voltage measuring unit; a current measuring unit that measures each phase current flowing to the shunt reactor inserted for each phase of the compensation transmission line; a current-zero-point-period detecting unit that detects a period of zero points of the phase current measured by the current measuring unit; and a closing-phase control unit that operates based on a closing command to the three-phase switching device, generates, for each phase, a closing phase in which the three-phase switching device is closed at zero points, both polarities of which are inverted into same polarity, among zero points where zero points of the voltage changing ratio and zero points of the shunt reactor current coincide with each other, and controls the three-phase switching device.