Patent ID: 9065268
Filing Date: 2015-06-23
Classification: H02H

Abstract:
1. An inrush-current suppressing device applied to a configuration in which three-phase alternating-current power is supplied to and cut off from a three-phase transformer having a primary winding of a Y connection via a three-phase breaker, for suppressing an excitation inrush current that possibly occurs in the three-phase transformer during input of the three-phase breaker, the inrush-current suppressing device comprising: a residual-magnetic-flux calculation unit that obtains a residual magnetic flux in each phase generated within the three-phase transformer based on a voltage of each phase generated in the three-phase transformer before and after closing the three-phase breaker; an input magnetic-flux-error calculation unit that obtains a closing-phase input magnetic-flux error for every phase based on the residual magnetic flux in each phase and in consideration of pre-arc characteristics and closing-time variation characteristics of the three-phase breaker; a closing-order determination unit that determines a closing order of phases of the three-phase breaker based on the residual magnetic flux in each phase; a target-closing-phase setting unit that calculates a phase in which the input magnetic-flux error in a first closing phase determined by the closing-order determination unit becomes a minimum value and sets the calculated phase as a target closing phase of the first closing phase, and that calculates a phase in which the input magnetic-flux error in the two remaining phases becomes a minimum value while assuming a predetermined phase in a predetermined reference phase as a reference point and sets the calculated phase as a target closing phase of a second closing phase; a target-closing-time setting unit that sets a time from the reference point to the target closing phase of the first closing phase as a target closing time of the first closing phase, and that sets a time obtained by adding up a time from the reference point to the target closing phase of the two remaining phases and a predetermined delay time as a target closing time of the second closing phase; and a closing control unit that generates a closing control signal and outputs the closing control signal to the three-phase breaker so as to close each phase at the target closing time of each phase set by the target-closing-time setting unit in response to a closing instruction to the three-phase breaker, wherein the predetermined delay time is set to exclude a period in which a magnetic flux in the first closing phase possibly saturates because of the input magnetic-flux error in the first closing phase.