Excess conduction induced by partial discharge in polymer

Abstract

The classical dipole model of partial discharge (PD) explains the relationship between the internal pulse charge and detected charge on the terminal, which is essential to assess the PD severity. However, the subsequent behavior (such as transport and dissipation) of the deposited charges generated during the PD process is still uncertain, which is likely to be an inducement in the degradation of the dielectrics. Some earlier studies tried to separate the movement of the deposited charge from the PD-induced current, but its kinetics still remain unclear. In this work, a measurement is designed to acquire the charge deposited during PDs under an alternating-electric field at low temperatures, giving insight into the subsequent behavior of PDs on epoxy films. Then, a charge transport model is established to explain the observed charge movement, according to which the dissipation of the deposited charges is explained as an excess conduction phenomenon during PDs and is affected by temperature. This excess conduction releases a part of the space charge accumulated in the polymers, but causes an excess conduction loss beyond bulk dielectric loss, which is regarded as an abnormal aging inducement. While at low temperature, excess conduction is suppressed, and trapped charges become a critical factor for degradation.