Electrical breakdown in composite insulating systems: Liquid-solid interface parallel to field

Abstract

A study is presented which identifies some of the characteristics of electrical breakdown at a liquid-solid interface. The primary emphasis is on paper interfaces in transformer oil and studies are performed using impulse and using 60 Hz waveforms. The interfaces are parallel to the electric field. Several cylindrically-symmetric electrode geometries are employed ranging from plane-plane to sphere-sphere. The electrode system is split along the symmetry axis to hold the paper parallel to the field. Among the conclusions drawn from this study are the following: First, the breakdown frequently occurs at positions other than the interface for both impulse and 60 Hz waveforms. Second, no significant difference is identified between the breakdown voltage with or without an interface in the system or between the breakdown voltage when a breakdown occurs at an interface and when it does not.