Abstract
A probe method is described for measuring conductance of hot gas ejected from a molded case circuit breaker during arc interruption process. Two steel rods of lmm diameter were adopted as probing electrodes, then being located near to an exhaust hole of the hot gas. Ratio of a current passing through gap between the probing electrodes to a voltage across them gives an apparent conductance of the hot gas. Net conductance was estimated from the apparent value with consideration of cool gas layer near to the probing electrode surface. The net conductance gnet proved to increase markedly from 0.6 to 2.3mS by a factor of 4 with a rise of a peak value Ipeak of an arc current from 6.5 to 8.8kA. The electrical conductivity a was then estimated from gnet by taking into consideration of the effective cross-section of the measurement area of the probe method. The electrical conductivity σ was found to grow from 0.071 to 0.27 S/m with increasing Ipeak. Above results suggest that the probe method is much more useful as means of assessing the ejected hot gas.
