THE MECHANISM OF THE BARRIER EFFECT IN SOLID DIELECTRICS

This paper presents results of a study of the barrier effect in solid dielectrics in uniform and highly inhomogeneous electric fields. The i nfluences of various factors such as mechanical strain, the position o f the barrier in gap, space charge, the permittivity and the conductiv ity gradient both on the breakdown voltage (V-b) and breakdown time (t au(b)) in the uniform field and on the tree-initiation time (tau(i)) i n the strongly inhomogeneous field were investigated. Application of b arriers with high permittivity may result in a significant increase in tau(b) not only by virtue of there being an increase in the tree-grow th time (tau(g)) but also because of an increase in tau(i). It was dis covered that the re-distribution of the field in the sample volume at the stage of initiation of failure plays a major role in the barrier e ffect. An analysis of existing models of the barrier effect is present ed.