New techniques for on-line partial discharge testing of solid-insulated outdoor MV and HV plant

The authors present a paper detailing new techniques for on-line partial discharge (PD) testing of in-service, solid- insulated, medium and high voltage plant located in outdoor environments. Detection of electromagnetic radiation is a well known and documented method for location of PD signals. However interference signals from RF sources, corona and surface discharges can be a major problem when testing outdoors, obstructing the observation of internal PD and confusing measurements. Experience in these situations has led to the development of various new tools and test techniques for PD identification and discrimination of interfering signals and background noise. Shielding sensors have been employed with a multi-channel measurement system to assist in detecting signals that are external to the equipment under test with time-of-flight (TOF) analysis. Methods for automating the test procedure and data analysis have also been a key part in this research and will be fundamental to future developments.