Dielectric Materials for Electrical Engineering

Chapter 10

Response of an Insulating Material to an Electric Charge: Measurement and Modeling 1

10.1. Introduction

In this chapter, we will take an interest in the observable response of an insulator subjected by its environment to different configurations of charge and electric field. The application of a DC stress was favored here, but the results presented could be extended to the case of a low frequency AC stress.

The response generally depends on a superposition of the internal mechanisms presented in the previous chapters. The material displays a specific order at the atomic scale (more or less deducible from its chemical formula), a structure at the nanometric scale due to the interactions between neighboring molecules (in the case of polymers), defects and impurities, a structure at the micrometric scale (spherulites for polyethylene, grains for polycrystals), together with surface phenomena, free surfaces, voids, and possibly interfaces when dealing with composite materials. Phenomena at each of these scales will have an influence on the general behavior of the insulator, at least in given conditions of field, pressure or temperature.

Research scientists know that theory in this domain is generally not able to predict accurately, for a given material, the results of even a simple an experiment. Therefore, our only ambition here is to show, with examples, what the phenomenological descriptions of the most frequent insulation behaviors are and on which physical hypotheses ...