PD Mechanism Analysis in Oil-Pressboard Insulation with Needle-Plate Defect at Positive DC Voltage Based on Field-Circuit Joint Simulation

PD Mechanism is the theoretical basis for studying PD pulse characteristics and insulation diagnosis by PD. In this paper, a laboratory experiment for studying the PD pulses in oil-pressboard insulation by simulating a needle-plate model with positive DC voltage was performed; PD pulses were detected by a non-inductive resistor. The bipolar charge transport model and the hydrodynamic drift-diffusion model are used to simulate the streamer. Then the circuit model is built based on the streamer evolution to simulate the PD pulse, and PD mechanism is finally analyzed quantificationally. The main conclusions are: PD pulses in oil-pressboard insulation by simulating a needle-plate model at positive DC voltage are unimodal, their rising edge corresponds the process of oil gap breakdown (streamer propagation), and their falling edge corresponds the charge accumulation process at oil-pressboard interface (streamer interruption). The PD pulse essentially is the current pulse generated in coupling loop due to the defect, partly shorted by streamer, being charged.