II — Factors affecting insulator sparkover

WHILE the mechanical properties and strength of the various parts entering into the design of a modern transmission system are quite well known, the electrical characteristics of the various parts often are not so definitely understood. This is true particularly of the electrical properties of the insulating parts, including the line and station insulation and bushings used in the station equipment. In this article are presented data on the sparkover strength of the various parts used for the insulation of modern high voltage transmission systems. Results are given of tests made to determine how insulator sparkover is affected by various factors.