Electrical Breakdown of Liquid Dielectrics

Abstract

Assuming that electron emission from the cathode and collision ionization in the liquid are both necessary for the electrical breakdown of liquid dielectrics, a criterion for breakdown is developed in which the cumulative effects of the applied field and the space-charge field of the positive ions produce a continuously increasing electron current at the cathode. The present theory differs from earlier similar theories in that the ionization occurring in the liquid is considered to be very small even at breakdown, in agreement with recent conduction measurements. The breakdown criterion shows clearly how the measured electric strength can depend on either the cathode or the liquid. The influence on the breakdown measurements of dissolved oxygen is also discussed, and the quantitative predictions of the theory are compared with measurements of the electric strength of liquid argon.