A Swing Relay for the East-West Intertie

Closure of the ties to interconnect power systems across the continent has imposed new relaying problems for which new solutions have been developed. A special relay has been monitoring the East-West Intertie since it was reestablished December 3, 1967. It is designed to sense conditions of the interarea tie and to anticipate when interchange is approaching difficulty. Power, rate-of-change of power, and oscillation quantities are employed. The relay, installed at the Yellowtail Power Plant in Montana, also effects transfer tripping at Fort Peck, Mont., and at Stegall, Neb., for prompt, clean East-West separations with minimum disturbance to the systems.