This standard applies to the Class 1E portions of the following systems and equipment in single unit and multi-unit nuclear power generating stations: (1) Alternating current power systems (2) Direct current power systems (3) Vital instrumentation and control power These systems include those items listed in Table 1. This standard also contains requirements for non-Class 1E 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 of this standard is to provide: (I) The principal design criteria and the design features of the Class 1E power systems that enable the systems to meet their functional requirement under the conditions produced by the applicable design basis events (2) The requirements for surveillance of the Class 1E power systems.