Reliability and long time behaviour of MV-distribution switchgear in severe environmental conditions — Examination of SF6-insulated ring main units (RMU) up to 20 years in service

SF6 insulated RMUs are designed and tested for operation in severe environmental conditions and have proven its reliability on thousands of units in service since 1983. International standards give only limited recommendations of how to test switchgears for special and severe environmental conditions and which risks have to be considered for an expected life time of more than 30 years.