Experimental Study On The Developing Processes Of Needle Plate Discharges On Oil-paper Insulation

Partial discharge can be used to evaluate insulating condition of electrical equipment.How to identify the severity grade of partial discharges (PD) in oil-paper insulation system is a key problem in high voltage and insulation technology area. The thesis built a simulating system and a measuring system to simulate partial discharges of oil-paper insulation and acquire conventional pulse current signals, UHF signals and UWB pulse current signals. The parallel structure and vertical structure of two kinds of needle plate discharge model were studied by step-up voltage method.The developing process of discharge was observed combined with pressboard traces of carbonation.The results indicate that with changing of voltage class and duration, the times of discharges, the average amplitude, the maximum amplitude and discharge spectrums appear to be different variation trend. In the discharging process of vertical structure model,discharge stagnation was observed. With the increae of the applied votltage time,some white marks can be observed on the surface of the insulation pressboard. In the discharging process of parallel structure model,the same stagnation phenomena appear.Discharge appears around the earth electrode and we can hear the sound of diacharging.These symbolic variations offer the experimental foundation for the research of the developing process of needle-plate discharge on oil-paper insulation.