Environmental humidity conditions for enclosed high-voltage switchgear. New test procedures, definitions and service experience

A survey found that condensation of humidity from the surrounding air will always lead to partial discharge currents at the surface of insulating components in enclosed high-voltage switchgear. IEC Publication 721 has presented a new catalogue of classes for the definition of environmental conditions. IEC Report No. 932 presents different test procedures to simulate the influence of condensation on insulating components of metal-enclosed high-voltage switchgear. The philosophies behind the different procedures are explained. Test procedures with defined humidity conditions can be carried out only with a specially developed test equipment. The lay-out and the main components are described. Modern types of switchgear are expected to be less sensitive with respect to environmental conditions. For existing switchgear, measures are proposed to increase or maintain safety and reliability in service. A new diagnostic system is under test