Classification of partial discharges for DC equipment

Computer aided partial discharge detection, recognition and classification at AC voltage has become common practice in recent years. Characteristic discharge phase distributions have been found, thus providing the possibility to recognise and assess possible defects in HV apparatus. For diagnostic purposes, fingerprints from these distributions can be derived and compared to those previously ascertained and stored in a data-bank. For DC voltage a similar technique can be used when the phase angle is replaced by the time between discharges. Successful results have been obtained by employing this method on several artificial defects.