Reproducibility of the Results of Partial Discharge Measurements according to IEC 60270 at DC and AC Voltage

Abstract:
The partial discharge measurement at AC voltage is one of the most important diagnostic tools for testing and assessing the condition of high voltage components. The requirements for the measuring system, the measuring setup and the test procedure as well as the evaluation methods are defined in IEC 60270. However, partial discharge measurements with DC stress are today not fully considered in IEC 60270, due to missing experience and information on the application. However, the partial discharge measurement under DC voltage will become more and more important, because of the increasing use of HVDC systems in the future transmission networks. Therefore, in a round-robin test the applicability of IEC 60270 for partial discharge measurements with DC voltage was investigated. After measurements on defective epoxy-resin insulators with voids at the City University of Applied Science in Bremen, the Graz University of Technology and the Leibnitz University of Hannover further measurements on a more simple test setup have been carried out. A feasible and reproducible measurement procedure was therefore developed and necessary definitions in the interpretation and evaluation of the measured data were being determined. Characteristic and quantities of AC and DC partial discharges were achieved, as well as the amplitude and number of discharges. The partial discharge behavior at a needle-plate arrangement at AC and DC voltage was investigated at the mentioned laboratories and compared in order to revise the applicability of partial discharge measurement at DC voltage. In this paper the results of these tests are analyzed, compared and open questions are asked and discussed.