Transformer inrush current suppression apparatus with function of determining target closing phase of three-phase transformer based on pre-arc characteristic and variation in closing time of the three-phase circuit breaker

Abstract

A target closing phase determining circuit determines energization flux errors in respective phases and respective closing phases of a first phase, and determines a target closing phase of the first phase so as to minimize an evaluated value related to determined energization flux errors in the respective phases. Each of the energization flux errors is the maximum value of absolute values of center values of transformer fluxes generated in a static state after energization. The target closing phase determining circuit determines the energization flux errors based on residual flux values for the first to third phases of a three-phase power supply, respectively, a pre-arc characteristic and a closing time variation characteristic of a three-phase circuit breaker, a connection condition of windings of a three-phase transformer, to which the three-phase circuit breaker is connected, and voltage phase differences among the phases of the three-phase power supply.