New approach to flashover in dielectrics based on a polarization energy relaxation mechanism

Abstract

The polaron concept is used to describe trapping of charge in a dielectric medium. It is shown that trapping is associated with defects identified as being due to a local decrease of the electronic polarizability. The polarization energy around a charge is estimated, using a self-consistent calculation of the local field. In nonpolar dielectrics this energy is 5 eV per charge, in the limit of validity of the Clausius-Mosotti relation. In polar dielectrics it can be much higher. A flashover process is proposed as resulting from the destabilization of the space charge by a variety of perturbations (electrical, mechanical, thermal), followed by the mechanical relaxation of the lattice, initially polarized by the charge.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>