Abstract
Partial discharge inception voltage-time (V-t) characteristics of transformer insulation partial model were investigated systematically to contribute in deciding the AC test voltage for the UHV transformer. This research covered the wide time range from several tens of milliseconds to several months. As a representative insulation model of the the transformer, turn-to-turn, coil-to-coil and barrier insulation ones were used.
Further characteristics towards trapezoidal voltage waveforms were studied as well as the standard AC waveform, when attention was put on the overvoltage occuring in load rejection As a result, quite precise data on V-t characteristics were obtained and got available to discuss the AC test voltage.
