Space charge and its impact on DC breakdown of polymeric materials

Abstract

The presence of space charge will lead to distortion of electric field distribution within the dielectric material, resulting electric field enhancement in certain region of the dielectric. The electric field enhancement could cause material degradation, even premature failure. In this paper the simulation of charge dynamics in polyethylene based on the observed negative differential mobility has been carried out using the bipolar charge injection model. Assuming that the maximum electric field governs the breakdown event in the material, the simulation results show that the applied electric breakdown strength is thickness dependent during a ramping breakdown test. The thickness dependent breakdown strength has been experimentally observed and widely reported in literatures but the mechanisms have never been fully explained. Our model indicates that the space charge formation and its movement within the material are responsible for the effect of sample thickness on electric breakdown. Accumulation of positive charge in the region near to the anode leads to a local high field, which may initiate the breakdown when it reaches the breakdown strength of the material. Our recent experimental observations of space charge dynamics up to breakdown in different thick samples strongly support the influence of space charge on electric breakdown.

More information

Identifiers

Catalogue record

Export record