Space charge and orientational polarization within epoxy as probed by the Pulsed Electro-Acoustic technique

The Pulsed Electro-Acoustic technique, which allows probing the space and time dependence of charge density within insulators, has been applied to probe polarization and space charge phenomena within an epoxy resin under direct current stress. The response appears as a superposition of orientational polarization, due to the polar nature of epoxy resins, and space charge accumulation, both exhibiting a dynamic character considering either polarization or depolarization experiments. Attempts have been made to separate these two contributions to the space charge profile and to reconcile transient currents that can be estimated from the time dependence of space charge and those obtained from external circuit measurements. The influence of the nature of the electrodes that are used for achieving measurements on the nature of space charge is also discussed in this work.