1 Scope

This part of IEC 63346 specifies common rules and requirements for the design of low voltage (LV) AC auxiliary power systems (APSs) intended to be installed in substations, mainly covering the configuration of AC power sources, system wiring, protection, electric equipment selection and physical layout.

For the purpose of interpreting this document, an AC APS in this document is considered as follows:

• with a nominal voltage up to and including 1 kV AC;

• providing LV AC power to substation AC loads.

Though it is discussed where necessary, AC loads as well as high voltage (HV) part is beyond the scope of this document.

Substations in this document refer to those which are part of an electrical system and contain equipment that either receives and distributes electrical energy or transforms voltages to the levels required by the loads they supply, or both.

This document does not apply to the design of any of the following:

• traction substation, which have different power supply requirements, such as unbalanced load power supply;

• offshore substations, as factors such as waves, typhoons, salt spray, etc. need to be taken into account, which have different requirements for power supply and equipment selection;

• the substation connecting a nuclear power plant to the grid and its associated LV APS integrated with the nuclear power plant.