This part of IEC 62271 applies to all switchgear and their assemblies for alternating current of rated voltages of 72,5 kV and above for indoor and outdoor installation, including their supporting structure rigidly connected to the round. Where switchgear and their assemblies are not ground mounted, e.g. in a building, conditions for application are subject to agreement between users and manufacturers. The seismic qualification of the switchgear and their assemblies take into account any auxiliary and control equipment either directly mounted or as a separate structure. This standard provides procedures to seismically qualify ground mounted switchgear and their assemblies for rated voltages of 72,5 kV and above. The seismic qualification of the switchgear and their assemblies is only performed upon request. This standard specifies seismic severity levels and gives a choice of methods that may be applied to demonstrate the performance of high-voltage switchgear and their assemblies for which seismic qualification is required.