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This paper presents results of a study of the barrier effect in solid dielectrics in uniform and highly inhomogeneous electric fields. The influences of various factors such as mechanical strain, the position of the barrier in gap, space charge, the permittivity and the conductivity gradient both on the breakdown voltage and breakdown time in the uniform field and on the tree-initiation time in the strongly inhomogeneous field were investigated. Application of barriers with high permittivity may result in a significant increase in not only by virtue of there being an increase in the tree-growth time but also because of an increase in . It was discovered 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 effect. An analysis of existing models of the barrier effect is presented.

In this paper, the experimental results of the study of the behaviour of three-layer solid dielectrics in high electric field are presented. The breakdown voltage and the breakdown channel forms depend on factors such as the position of the boundaries between layers in the gap, the ratio of permittivities of layer materials, and the homogeneity of barrier materials. It was found that polarization plays the main role in the barrier effect.

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