Abstract
As a transformer fault diagnostic method at impulse voltage test, directly comparing possible variance in impulse voltage wave form and current wave form under two different conditions, namely at reduced voltage and predetermined voltage has long been and, still is, commonly practiced.
With the recent improvement in digital measuring techniques, a new diagnosis method by comparing resonance frequencies is also expected. The new method is based on comparing resonance frequencies which are derived from frequency transfer function which in turn is calculated from voltage and current wave forms converted to frequency ranges. In the event that the specimen transformer has failed in the impulse voltage test, the impulse voltage wave form should show rapid voltage drop and the current wave form should show increase in direct current component. In the frequency range, on the other hand, resonant frequency of frequency transfer function should change.
In this paper, we have attempted to compare these two fault diagnosis methods, namely direct wave form comparison method and frequency transfer function method, based on the results of wave form simulation and simulated fault test using transformer model. As a result, it has been confirmed that both of the method can diagnose not only whether or not fault has occurred but also the magnitude of the fault.
