Numerical analysis of steady‐state thermal breakdown

A procedure for numerically solving the fundamental equations of steady‐ state thermal breakdown has been presented. Assuming an ionic conduction and using the published experimental conduction data for poly (ethylene–terephtalate) film, the current–voltage characteristics, the temperature dependence of the critical electric field, and the profiles of temperature and field in the bulk at a constant ambient medium temperature are given. The calculations indicated that moderation of field distortion occurs if a nonlinear field dependence of conduction current is used in place of Ohm’s law. The degree of the moderation of field distortion depends on the functional form of the temperature and field dependence of conduction current and the magnitudes of parameters involved therein. Unless these are established and a quantitative evaluation of the thermal breakdown process based on them are made, thermal breakdown cannot be excluded as a possible mechanism for thick samples of polymers.