This standard applies to those parts of the electric systems in stationery single-unit and multi-unit 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" (1) alternating-current power systems, (2) direct-current power systems, (3) vital instrumentation and control power systems. These systems consist of power supplies (e.g., connections to the station switchyard, stand-by generators, batteries), distribution equipment and components (e.g, transformers, switchgear, bus cable, battery chargers, inverters), and instrumentation and controls (e.g., relays, meters, switches, control devices). This standard does not apply to the unit generator(s) and their buses, step-up and auxiliary transformers, switchyard, transmission lines and transmission network.