This part of IEC 62271 applies to gas-insulated switchgear assemblies for alternating current of rated voltages above 52 kV for indoor and outdoor installations, including their supporting structure. For switchgear devices, e.g. live tank circuit breakers, IEC/TR 62271-300 is applicable. Guidance on interactions between the supporting structure and the soil / foundations is provided in Annex B. The seismic qualification of the switchgear assemblies takes into account testing of typical switchgear assemblies combined with methods of analysis. Mutual interaction between directly mounted auxiliary and control equipment and switchgear assemblies are covered. The seismic qualification of switchgear assemblies is only performed upon request.