Diagnosis of insulation conditions : Interpretation of partial discharges from φ-q-n pattern, pulse-sequence and pulse waveform

Appearance of electrical discharges in high voltage apparatuses with reasonable magnitude and frequency can be interpreted as abnormal condition. The discharge may take place in several types. Firstly, corona discharges which represents abnormal electric stress on a conductor. Secondly, void discharge which represents discharge take place in a gas filled void in solid or liquid insulation. Thirdly, treeing discharge which takes place in tree channels inside a solid insulation. This paper reports experimental results on the three kinds of discharges. The analysis was focused on the phi-q-n pattern, the time sequence between consecutive pulses and the waveform of a discharge pulses. The difference among them maybe useful to diagnose of insulation condition.