Excitation inrush-current suppression system

摘要

According to an embodiment, when a transformer that is connected to a first power supply through a first breaker as well as to a second power supply through a second breaker is detected to be disconnected from the power supplies, a specific phase of the three phases of the first breaker is closed to suppress an excitation inrush current, based on calculated residual magnetic fluxes and a voltage of the first power supply, and thereafter, the remaining two phases are closed. Based on the calculated residual magnetic fluxes and a voltage of the second power supply, a specific phase of the three phases of the second breaker is closed to suppress an excitation inrush current, and thereafter, the remaining two phases are closed.

主权项

1. An excitation-inrush-current suppression system that suppresses an excitation inrush current of a transformer connected through a first breaker to a first power supply and connected through a second breaker to a second power supply, the system comprising:
a transformer-voltage measurement unit configured to measure three-phase alternating-current voltages of the transformer; a transformer power-off detection unit configured to detect that the transformer is disconnected from the power supplies; a residual magnetic flux calculation unit configured to calculate residual magnetic fluxes of three phases of the transformer, based on the three-phase alternating-current voltages measured by the transformer-voltage measurement unit, when the transformer is detected to be disconnected from the power supplies by the transformer power-off detection unit; a first power-supply-voltage measurement unit configured to measure three-phase alternating-current voltages of the first power supply; a first closing unit configured to close a specific phase of the three phases of the first breaker at a first closing phase for suppressing an excitation inrush current, the specific phase being either a phase having a maximum absolute value or a minimum absolute value among the residual magnetic fluxes of the three phases, based on the residual magnetic fluxes of the three phases of the transformer calculated by the residual magnetic flux calculation unit and the three-phase alternating-current voltages of the first power supply measured by the first power-supply-voltage measurement unit; a second closing unit configured to close two phases other than the specific phase of the first breaker, at a second closing phase for suppressing an excitation inrush current, after closing the specific phase of the first breaker by the first closing unit; a second power-supply-voltage measurement unit configured to measure three-phase alternating-current voltages of the second power supply; a third closing unit configured to close a specific phase of the three phases of the second breaker at a third closing phase for suppressing an excitation inrush current, the specific phase being either a phase having a maximum absolute value or a minimum absolute value among the residual magnetic fluxes of the three phases, based on the residual magnetic fluxes of the three phases of the transformer calculated by the residual magnetic flux calculation unit and the three-phase alternating-current voltages of the second power supply measured by the second power-supply-voltage measurement unit; and a fourth closing unit configured to close two phases other than the specific phase of the second breaker, at a fourth closing phase for suppressing an excitation inrush current, after closing the specific phase of the second breaker by the third closing unit.