IEC TS 63346-2-2:2026 provides common rules and specific requirements for the design of low voltage DC auxiliary power systems (APSs) intended to be installed in substations, mainly covering the configuration of DC power sources, system wiring, electric equipment selection and physical layout. For the purpose of interpreting this document, a DC APS in this document is considered as follows.
Its scope covers from the low voltage AC input of the charger to the DC input points of loads. Though DC load is discussed where necessary, the load itself is beyond the scope of this document.
Unless particularly stated, DC APS refers to the system using lead-acid and nickel-cadmium cells which are connected in series. The system using parallel cells can implement this document by reference.
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 and harmonic behaviour;
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.
