| 摘要 |
PROBLEM TO BE SOLVED: To discriminate a failure current and an excitation rush current clearly regardless of power system constitution, by judging an inner defect when a difference from a magnetization curve calculated from characteristics of a transformer core and physical characteristics of a circuit is over a given level. SOLUTION: Whether an absolute value|I|of an instantaneous sample value as the sum of current to each winding is over 30% of a rating current 10 or not is detected. (S1) Namely, whether a difference current is over 30% or not is detected. When the difference current over 30% of the rating current is carried (S1) and the difference current|I|is over 300% of the rating current 10 (too large as an in-rush current) or a secondary harmonic factor is 15% or below of a fundamental wave, an inner failure is judged and the detecting steps are finished. (S2) In this way, a failure current and an excitation rush current can be discriminated clearly, regardless of power system constitution.
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