This guide is developed to assist users in selecting the appropriate level of protection system redundancy for power system reliability based on the best industry practices. It defines protection system redundancy and examines the effect of protection system components on redundancy. Different concepts of redundancy as related to physical location, instrument transformer, relay scheme, and communication systems are discussed. Redundancy application considerations for various power system elements are presented. (An errata for this standard is available at https://standards.ieee.org/wp-content/uploads/2022/12/C37.120-2021_errata.pdf)

This guide provides information about what factors to consider when determining the impact of protection system redundancy on power system reliability.

The purpose of this guide is to provide information on protection system redundancy considerations by illustrating the purpose of redundancy and how it may be implemented in the protection system design.