Correlation of AC, switching surge and DC breakdown test results for insulating blankets and line hoses

Information reported during the ESMO-90 panel session, entitled Rationale for Test Criteria of Live-Line Maintenance Protective Equipment is presented. The rationale for electrical testing of live line maintenance tools, in particular, the insulating protective equipment (IPE), such as insulating blankets and line hoses, is discussed. The present status of such testing is compared to the existing standards. The main thrust is the presentation of test results from a special international test program involving ten laboratories. Data are given on the breakdown voltage correlation between power frequency, direct current, and switching overvoltage tests. The results indicate that the equivalence in testing between power frequency and DC, and power frequency and switching overvoltage now used in the industry and standards may be incorrect