A simple method considering the synergetic effect of space charge and inhomogeneous material conductivity for DC electric field computation

Abstract

The current continuity equation is usually applied to solve DC electric field distribution when there is inhomogeneous material conductivity due to temperature gradient or multi-layer dielectrics. However, in the presence of charge accumulation, which may result from the process of electrode injection, impurity ionisation or charge trapping, the material conductivity is in tangled relationship with local field strength, and the current continuity equation can be hardly applied due to the ignorance of conductivity distribution. Thus, quantitative analysis on the effect of space (surface) charge for DC apparatus with inhomogeneous material conductivity has been a difficult problem, which requires a complicated physical model to solve. This paper has proposed a simple method to compute the synergetic influence of inhomogeneous conductivity and the space charge on the DC field distribution; through assigning bulk (interface) charge as functions of local material conductivity and field strength, the effect of inhomogeneous conductivity can be incorporated in Gauss' law and the space charge accumulation can be further included in the equation. The effect of space (surface) charge on electric field distribution in DC apparatus with temperature gradient as well as multiple-layer dielectrics is simulated through the proposed method, which shows that the method has offered a convenient approach for investigating the effect of charge accumulation on DC field distribution under various insulation structure and working conditions.