Utility cooperation in metalclad switchgear insulation tests and standards

HV apparatus, is subjected to deteriorating influences in service. An installation, perfectly adequate when new, can lose much of its initial integrity and reliability after years of exposure to corona (in bushings, instrument transformers, compartment panel feed-throughs), temperature cycling (all components, particularly severe for outdoor metalclads), and to contamination conducive to tracking (on surfaces of bus insulation and insulating panels, sometimes in bushings).