Testing of solid-core insulators for use on br 25 kV electrification

A salt-fog test for porcelain insulators is described and results are presented which compare it with the wet test in BS137 as a means of determining the suitability of an insulator for use on BR. It is maintained that the salt-fog test is a superior technique and, furthermore, can be used as a research tool for optimising shed design. A relationship is derived which equates natural pollution levels in service with the salt-fog withstand levels applied in the laboratory, and values of salinity are quoted which porcelains must withstand before being accepted for use on BR.