This Standard applies to those parts of the electric systems in stationary land-based nuclear power generating stations that provide electric power to the Class IE electric equipment. The electric systems included are comprised of the following interrelated systems: (a) alternating-current power systems@ (b) direct-current power systems@ (c) vital instrumentation and control power systems. These systems consist of power supplies (e.g.@ connections to the station switchyard@ generating units@ batteries)@ distribution equipment and components (e.g.@ transformers@ switch gear@ bus@ cable@ battery chargers@ inverters)@ and instrumentation and controls (e.g.@ relays@ meters@ switches@ control devices). This Standard does not apply to the station generator@ generator buses@ step-up and auxiliary transformers@ switchyard@ the transmission lines@ and the transmission network.PURPOSE The purpose of this Standard is to provide : 1) The principal design criteria and the design features of the Class IE electric systems that enable the systems to meet their functional requirement under the conditions produced by the design basis events@ 2) The minimum operational conditions of the Class IE electric systems under which the station will be permitted to operate@ 3) The surveillance requirements of the Class IE electric systems.