In order to better study the charge distribution characteristics of partial discharge of needle electrode in oil-paper insulation system under DC voltage

this paper builds a simulation model based on hydrodynamic diffusion-drift equation and bipolar charge transport equation to simulate the distribution of space charge and study the charge.The process and discharge characteristics of the generated and streamed developments have led to the developmentof charge

electric field and potential during partial discharge. The research shows that the partial discharge processof the oil-paper insulated needle plate electrode is divided into two stages: the flow-breaking oil gap and the chargeaccumulation on the paperboard. During the breakdown of the oil gap

the electric field strength and net charge densi-ty of the flow head will increase continuously

forming a self-sustaining discharge

when the flow reaches the surfaceof the insulating paperboard and accumulates charge on the paper surface

a shielding layer will be formed

resultingin a weakening of the electric field distribution and charge distribution of the flow injection

gradually forming a zero electric field region

interrupting the flow injection

and generating a charge diffusion.