Space and Interface Charge Simulation of Oil-Paper Insulation with Multi-Layer Oil Gap and Insulation Pressboard

The accumulation of space charge inside and at the interface of oil-paper insulation could distort the electric field and cause energetic degradation. So far, two types of model are commonly used to describe space charge movement, which is unipolar charge transport model and bipolar charge transport model. In this paper, the authors presented a way to simulate the space charge movement of oil-paper insulation consists of multi-layer of oil gap and oil impregnated pressboard based on the bipolar charge transport model using upstream finite element method (FEM). The space charge movement simulation result of two layer "oil gap + oil impregnated pressboard" highly matches with the experimental result. With the simulation method been validated by the experimental, the following three layer "oil impregnated pressboard + oil gap + oil impregnated pressboard" and four layers "oil gap + oil impregnated pressboard + oil gap + oil impregnated pressboard" space charge movement simulations were performed. Based on the simulation results, a new model for determining the polarity at the interfaces between oil gaps and oil impregnated pressboard was concluded.