Arcing phenomena through hot gas ejected from moulded-case circuit breakers during the high-current interruption process

Are formation may occur through a hot gas ejected from a moulded-case circuit breaker (MCCB) between the source-side terminals of the MCCB. The formation of the are in the hot gas was studied. Electrodes of 1 mm diameter with a gap length of 3 mm were located near the exhaust hole of the hot gas to record the time variation of the conductance of the hot gas. The conductance was found to increase gradually for a time and then to rise abruptly on the occurrence of the arcing phenomenon. The arcing phenomenon was shown to occur when the gas conductance and the voltage applied across the hot gas reached 30 mS and 300 V respectively. From this critical conductance, the critical values of electrical conductivity and temperature were estimated to be 3.4-4.5 S m(-1) and 3800-4100 K, respectively.