Application of Circuit-Breaker Standards in Short-Circuit Current Calculation for Generator Circuit-Breakers

Interruption of fault current with delayed current zeros (DCZ) is one of the peculiarities of generator circuit-breaker (GCB) that differentiates it from other medium-voltage and high-voltage circuit-breakers. This paper aims to provide a guideline for precise calculation of short-circuit current requirements for GCB. The methods described in IEEE and IEC standards are analyzed and their impact on the selection of GCB is investigated. In particular, the standard IEC 60909, IEEE C37.010 and standards specific for GCB application IEEE C37.013 which is superseded by new dual logo standard IEC/IEEE 62271-37-013 are the scope of this paper. Calculation of two main interrupting duties of GCB are addressed: 1) generator-source short-circuit currents and 2) out-of-phase fault currents. Analytical results are verified with the simulation results obtained from ATP-EMTP. In conclusion, the question of which standard shall be used to accurately evaluate the short-circuit current requirements for the selection of a GCB is well-answered.