Application of Modern Relays to Dual-Breaker Line Terminals

This paper discusses several protection and control aspects in relation to dual-breaker line terminals. First, breaker failure and reclosing functions are discussed as applied to dual-breaker configurations. Second, the paper talks about protection security as related to saturation of current transformers (CTs) under fault currents flowing locally through the two breakers. New generation of microprocessor-based line relays support dual CT inputs to monitor both breakers individually, and three voltage points to provide for the main line protection, and synchrocheck across both breakers. The paper points to advantages and disadvantages of integration protection, and provides some guidance regarding dual-breaker line applications