Simulation Study on the Time-Dependence of Breakdown Strength in Insulating Polymers

On the basis of the percolation model for electrical breakdown in insulating polymers, a simulation approach was put forward for the process of electrical aging. The deteriorated regions formed by bond scission are expressed as the sites with lower trap barriers, and the local deterioration rate is related to both the electrical field and the size of existing deteriorated regions. Then the reduction of breakdown strength (or the percolation threshold) with the increase of deteriorated sites can be simulated. Assuming a parameter ß to reflect the effect of the size of existing deteriorated region, simulation results show two types of breakdown: percolation-like breakdown for ß¿2 (in which the percolation threshold is reduced due to the gradual global increase of deteriorated sites) and avalanche-like breakdown for ß>2 (in which breakdown occurs by the rapid growth of a filamentary structure). Moreover, the correlation between the aging time and the breakdown strength (i.e. the E-t curve) can be also investigated by this model.