Stress dependent conductivity of field grading materials under time varying electrical fields

In this paper the need for an accurate and simple mathematical model for characterizing nonlinear field grading materials (FGM) subjected to a time varying field is explained. It has been shown that the expression for steady state (DC) conductivity is not adequate, to deal with situations where the electric stress vary rapidly with time. Instead, it is proposed to introduce an additional partial differential equation of relaxation type for describing the time dependent behavior of the conductivity. An experimental set up is also discussed to acquire data for comparison of the model. The model is validated with preliminary experimental data obtained from the experiments.