IDENTIFICATION METHOD FOR EXCITATION RUSH-IN CURRENT PHENOMENON

PROBLEM TO BE SOLVED: To precisely identify an excitation rush-in current phenomenon even if the excitation rush-current is affected by noise, by precisely estimating a magnetic saturation start time or magnetic saturation finish time.SOLUTION: A transformer primary current after occurrence of instantaneous voltage drop is taken as a time series data at a predetermined sampling cycle. Time series data which gradually decreases for geometric convergence along the change direction from a saturation region of a transformer core to a no-saturation region, among the time series data that have been taken in, are extracted. An instantaneous voltage drop caused by the excitation rush-in current of a transformer is determined if an interlinkage magnetic flux of the transformer core at the time of magnetic saturation start time is equal to the interlinkage magnetic flux of the transformer core at the magnetic saturation finish time, with an increment current which is a difference between the estimated conversion value of Aitken square process on the time series data that has been extracted and converges geometrically as well as a measurement value of the convergence time as an index, and with a zero point of the increment current as the magnetic saturation start time or magnetic saturation finish time.