Electrical Trees in Solids

Abstract

Electrical trees are branched degradation structures caused by field enhancing defects in insulating materials and are a common precursor to their failure. In this article we describe their shape and physical nature, and discuss the mechanism whereby they are generated in the insulating material together with a number of theoretical models for their formation. The influence of a range of physical factors upon their initiation and propagation is outlined and the use of partial discharges in their diagnosis briefly described. The article ends with a statement of unresolved questions and recent work in this area which is focussed on the emerging nano‐composite materials.