Nature of partial discharges and their measurement

There are perhaps very few measurement techniques that have contributed as much as partial discharge detection in the evaluation of high voltage apparatus, devices and cables. Notwithstanding, the progress that has been achieved over the past several decades in the description and understanding of the various mechanisms that may precipitate electrical insulation system failure, corona or partial discharge measurements have retained their preponderant importance. This must to a large extent be attributed to the fact that cavity-type defects, introduced into the insulation system during the various manufacturing steps, can be readily detected by means of routine corona discharge tests — with the tacit proviso that such cavities undergo ionization and subsequent pulse-type discharge in order to activate the response of conventional corona pulse detectors.