Phase-control switching apparatus and switching control method for phase-control switching apparatus

A phase-control switching apparatus comprising:

• a breaker that is connected between an electric power system and a transformer and is controlled to cut off or energize the transformer;
• a voltage measuring unit that measures each phase voltage between the breaker and the transformer;
• a residual-magnetic-flux calculating unit that calculates a residual magnetic flux remaining on the transformer;
• and
• a control unit that controls a switching timing of the breaker based on the residual magnetic flux, wherein
• the residual-magnetic-flux calculating unit includes
• a voltage-change-rate detecting unit that detects an average value in one period of a transformer-voltage change rate for each phase obtained by differentiating the phase voltage with respect to time, and
• a residual-magnetic-flux detecting unit that detects the residual magnetic flux based on the phase voltage, and
• the residual-magnetic-flux detecting unit determines a switching state of the breaker based on a predetermined first threshold and the average value of the transformer-voltage change rate, when it is determined that the breaker is in an open state, determines whether to recalculate the residual magnetic flux based on a predetermined second threshold that is different from the first threshold and the transformer-voltage change rate, and when it is determined to recalculate the residual magnetic flux, recalculates the residual magnetic flux.

A switching control method for a phase-control switching apparatus, wherein

• the phase-control switching apparatus includes
• a breaker that is connected between an electric power system and a transformer and is controlled to cut off or energize the transformer,
• a voltage measuring unit that measures each phase voltage between the breaker and the transformer,
• a residual-magnetic-flux calculating unit that calculates a residual magnetic flux remaining on the transformer based on the phase voltage, and
• a control unit that controls a switching timing of the breaker based on the residual magnetic flux, and
• the switching control method comprises:
• detecting including the residual-magnetic-flux calculating unit calculating a transformer-voltage change rate for each phase obtained by differentiating the phase voltage with respect to time;
• first determining including the residual-magnetic-flux calculating unit determining a switching state of the breaker;
• second determining including the residual-magnetic-flux calculating unit determining whether to recalculate the residual magnetic flux based on the transformer-voltage change rate when it is determined that the breaker is in an open state;
• and
• recalculating including the residual-magnetic-flux calculating unit recalculating, when it is determined to recalculate the residual magnetic flux, the residual magnetic flux.

A switching control method for a phase-control switching apparatus, wherein

• the phase-control switching apparatus includes
• a breaker that is connected between an electric power system and a transformer and is controlled to cut off or energize the transformer,
• a voltage measuring unit that measures each phase voltage between the breaker and the transformer,
• a residual-magnetic-flux calculating unit that calculates a residual magnetic flux remaining on the transformer based on the phase voltage, and
• a control unit that controls a switching timing of the breaker based on the residual magnetic flux, and
• the switching control method comprises:
• detecting including the residual-magnetic-flux calculating unit calculating an average value in one period of a transformer-voltage change rate for each phase obtained by differentiating the phase voltage with respect to time;
• first determining including the residual-magnetic-flux calculating unit determining a switching state of the breaker based on a predetermined first threshold and the average value of the transformer-voltage change rate;
• second determining including the residual-magnetic-flux calculating unit determining whether to recalculate the residual magnetic flux based on a predetermined second threshold different from the first threshold and the average value of the transformer-voltage change rate when it is determined that the breaker is in an open state;
• and
• recalculating including the residual-magnetic-flux calculating unit recalculating, when it is determined to recalculate the residual magnetic flux, the residual magnetic flux.