Magnetizing inrush current suppressing device

A magnetizing inrush current suppressing device for controlling a circuit-breaker which opens and closes a connection between a three-phase transformer and a three-phase AC power supply and in which a capacitor is connected between poles of the circuit-breaker, to suppress a magnetizing inrush current, comprising:

• a transformer-side voltage measurement unit configured to measure a three-phase AC voltage on the three-phase transformer side of the circuit-breaker;
• a residual magnetic flux DC component calculation unit configured to calculate DC components of residual magnetic fluxes of three phases of the three-phase transformer after the three-phase transformer is shut down, based on the three-phase AC voltage measured by the transformer-side voltage measurement unit;
• a phase detection unit configured to detect, as a notable phase, a phase having one of a maximum absolute value and a minimum absolute value from among the DC components of the residual magnetic fluxes of the three phases calculated by the residual magnetic flux DC component calculation unit;
• a power-supply-side voltage measurement unit configured to measure a three-phase AC voltage on the power supply side of the circuit-breaker;
• and
• a closing unit configured to close the circuit-breaker,
• wherein the phase detection unit is configured to detect a first phase angle at which the detected notable phase of the three-phase AC voltage measured by the power-supply-side voltage measurement unit takes a peak value having a polarity opposite to a polarity of the DC component of the residual magnetic flux of the notable phase calculated by the residual magnetic flux DC component calculation unit;
• wherein the closing unit is configured to close the circuit-breaker at the notable phase by the detected first phase angle;
• wherein the phase detection unit is configured to detect a second phase angle at which the detected notable phase from the three-phase AC voltage measured by the power-supply-side voltage measurement unit becomes a zero point after the detected first phase angle;
• and
• wherein the closing unit is configured to close the circuit-breaker at two phases other than the notable phase by the detected second phase angle.