New techniques for on-line partial discharge measurements

In insulation condition monitoring of HV equipment, partial discharge (PD) might be one of the most effective techniques. Almost all insulation breakdowns start from partial discharges. Even for new equipment, PDs could exist and increase when the insulation is aged. Unlike other techniques that can only determine the average condition of an insulation system, partial discharge activities reflect local insulation problems and can provide accurate information about the deterioration rate in local areas. However, PD measurements on in-service equipment often fail because of the problem of interference. A new PD detector PDD-4 has been jointly developed by Monash University and Insultest Australia that uses advanced digital signal processing techniques, a new directional sensor and a multiple noise gating system for noise discrimination and blocking. In conjunction with a multiple terminal measurement technique, partial discharges of high voltage equipment such as transformers, generators and power cables can be more accurately measured.