This standard applies to the electric systems in stationary single-unit and multi-unit nuclear power generating stations that provide electric power to the Class IE equipment. The electric systems included are comprised of the following interrelated systems: (1) alternating-current power systems (2) direct-current power systems (3) vital instrumentation and control power systems These systems consist of power supplies (for example, standby generators and batteries), distribution equipment, and components (for example, transformers, switchgear, bus, cable, battery chargers, and inverters), and their associated instrumentation and controls (for example, relays, meters, switches, and control devices). This standard does not apply to the unit generator(s) and their buses, step-up, auxiliary, and start-up transformers, connections to the station switchyard, switchyard, transmission lines, and the transmission network.