ABNORMALITY DIAGNOSTIC METHOD FOR LOADED TAP-CHANGING TRANSFORMER

摘要

PROBLEM TO BE SOLVED: To diagnose abnormality of a tap-changer by obtaining time of short circuit between taps. SOLUTION: A primary current, secondary current and tap numbers of a loaded tap-changing transformer are detacted, and the primary current value -the secondary current value×the ratio of numbers of the primary and secondary turns is calculated. The time for a short circuit between taps is calculated from the obtained waveform to diagnose an abnormality. The tap numbers indicate the ratio of numbers of the primary and secondary turns. It there is much harmonic noise, precise start time and end time of the short circuit are determined to obtain the tap short circuit time by calculating a Fourier approximate waveform, having a waveform near the waveform at the maximum value of the harmonic noise from the obtained waveform and subtracting the Fourier approximate waveform from the obtained waveform. Consequently, failure and abnormal signs in a tap-changer are diagnosed.