The ``First Zero Interrupter´´ as an Alternative to the Fault Current Limiter

A simplified solution to the fault current limiter problem based upon fault current limitation after the first current loop, is formulated and examined in detail. A survey of key U.S. utilities has yielded significant quantitative information on short circuit capacity requirements, characteristic features of affected systems, and fault current statistics. Based upon consultation with manufacturers of transmission equipment and mathematical analyses, an assessment is made of the short circuit behavior of existing substation apparatus when subjected to higher-than-rated faults whose duration is limited to a single current loop. Circuit breaker contact behavior is identified as the major concern. A probabilistic analysis of a representative system discloses that in a system capable of developing a fault of 160% of interruption rating, the likelihood of subjecting a circuit breaker to instantaneous currents in excess of its close-and-latch rating is surprisingly rare.