Magnetizing inrush current suppression device

A magnetizing inrush current suppression device for controlling a circuit-breaker that closes and opens connection between a transformer having a Y-connected primary winding and Δ-connected secondary winding and a three-phase AC power supply to suppress a magnetizing inrush current, the magnetizing inrush current suppression device comprising:

• a power supply-side voltage measurement unit configured to measure three-phase AC voltage on a power supply side of the circuit-breaker;
• a prospective magnetic flux calculation unit configured to calculate prospective magnetic fluxes between three lines of the secondary winding of the transformer based on the three-phase AC voltage measured by the power supply-side voltage measurement unit;
• a transformer voltage measurement unit configured to measure respective terminal voltages of the secondary winding of the transformer;
• a residual magnetic flux calculation unit configured to calculate residual magnetic fluxes between the three lines based on the respective terminal voltages measured by the transformer voltage measurement unit;
• a minimum residual magnetic flux determination unit configured to determine residual magnetic flux of a minimum absolute value among the residual magnetic fluxes between the three lines calculated by the residual magnetic flux calculation unit;
• a closing phase determination unit configured to determine a phase position for suppressing the magnetizing inrush current among phase positions in which the prospective magnetic flux calculated by the prospective magnetic flux calculation unit and the residual magnetic flux calculated by the residual magnetic flux calculation unit coincide between the lines of the minimum residual magnetic flux determined by the minimum residual magnetic flux determination unit, as a closing phase position;
• and
• a closing unit configured to simultaneously close the three phases of the circuit-breaker at the closing phase position determined by the closing phase determination unit.