Considered in this guide are the components of both the ac and dc systems and the provided guidelines and recommendations for designing the appropriate systems for the substation under consideration. This guide includes the low-voltage auxiliary systems from the source(s) to the distribution point(s). Reliability requirements and load characteristics are discussed and distribution methods are recommended.

This Recommended Practice considers the components of both the ac and dc systems and provides guidelines and recommendations for designing the appropriate systems for the substation under consideration. This recommended practice covers the low-voltage auxiliary systems from the source(s) to the distribution point(s). Reliability requirements and load characteristics are discussed, and distribution methods are recommended.

The low-voltage ac and dc auxiliary systems comprise very important parts of the substation equipment. The design of the ac and dc auxiliary systems facilitates the safe and reliable operation of the substation. This recommended practice considers various factors that affect the design of the ac and dc auxiliary systems such as reliability, load requirements, system configurations, personnel safety, and protection of auxiliary systems equipment.