EHV Protective Relaying on SCEC System

The South Central Electric Companies (SCEC) system was one of the first operational 500-kV systems in the United States. The increased transmission capability of 500-kV systems emphasized the need for reliability and security of associated protective relaying facilities. Special considerations such as the protection of shunt reactors directly connected to the line and possibilities of higher percentage overvoltages than experienced on lower voltage systems were analyzed. At about the same time, static type protective relaying was being introduced as an improved type of protection. All of these factors are discussed in the development of the overall protective arrangement for the 500-kV lines and associated transformers.