Simultaneous Electrical and UHF Measurement of DC-PD from Point-Plane Defect

Partial Discharges (PD) have long been studied under AC field stress and are widely accepted as a good indicator of component health. However, the advent of HVDC brought new challenges, as the pre-existing knowledge in the area of PD is not applicable to DC. The discharge behavior has been found to be erratic and there is no plausible evidence yet, that correlates discharges with insulation deterioration. The inability to produce stable behavioral patterns in DC-PD has also led to a spark in interest in the application of several non-conventional measuring methods, e.g. the measurement using UHF sensors. Therefore, this paper deals with the measurement of time synchronized PD measurements through conventional electrical and UHF methods for a novel comparison of DC discharge patterns generated by a needle-plate electrode arrangement in air. The different configurations of the defect are studied under both voltage polarities and the observations are discussed in terms of pulse magnitude and repetition rate. In addition, this paper exploits the opportunities of computational power for post-processing to obtain Pulse Sequence Analysis (PSA) diagrams of the discharge data.