Simulations of three-phase faults at the generator terminals have shown the existence of non-zero currents in all three phases for several cycles. Particularly in the application of generator circuit breakers, there could be a serious problem in that the delayed current-zero phenomenon might inhibit normal circuit opening. This investigation was undertaken to develop a method of modeling the circuit breaker arcing characteristics and determine the influence of arc gap resistance on the normal fault current decay. The paper presents the fundamental theory of the non-zero current phenomenon along with the basic operation and modeling of typical air-blast circuit breakers.