This standard applies t o the Class I E portions of the following systems and equipment in single unit and multiunit nuclear power generating stations: (1) Alternating current power systems (2) Direct current power systems (3) Vital instrumentation and control power systems (4) Protective action systems These systems include those items listed in Table 1. This standard also treats requirements for non-Class IE interfaces such as the preferred power supply. This standard does not apply to the unit generator(s) and their buses@ generator breaker@ step-up@ auxiliary@ and start-up transformers@ connections to the station switchyard@ switchyard@ transmission lines@ and the transmission network. Purpose The purpose o f this standard is t o provide: (1) The principal design criteria and the design features of the Class I E power systems that enable the systems to meet their functional requirement under the conditions produced b y the applicable design basis events (2) The requirements for surveillance o f the Class I E power systems