Patent ID: 8093885

Claim:
A residual magnetic flux measurement apparatus, comprising: a DC-voltage-component calculation device configured to calculate a DC voltage component of a voltage from a three-phase transformer; a voltage integration device configured to calculate a voltage-integration signal by separating the DC voltage component from the voltage from the three-phase transformer; a magnetic-flux DC-component calculation device configured to calculate a magnetic-flux DC-component from the voltage-integration signal; a magnetic flux calculation device configured to calculate a magnetic flux signal by separating the magnetic-flux DC-component from the voltage-integration signal; a control device configured to stop, when contacts of circuit breakers on both sides for any one of the phases of the three-phase transformer are interrupted together, an update on the DC voltage component and the magnetic-flux DC-component, and to calculate, when a maximum absolute value of the voltage continues in a state of being a threshold value or less for a predetermined time period, as a residual magnetic flux a total sum of converged values of the magnetic flux signal after the circuit breakers' interruption; and the above devices being provided for each phase.