Experimental Study on Arc Interruption Characteristics of SF₆ and Its Mixtures With CF₄

The arc interruption characteristics of SF₆-CF₄ were investigated based on a detachable gas circuit breaker (GCB) model. The digital delay generator was used to control the operating mechanism of CB and thyristor etc. The shielding net was used to attenuate the electromagnetic interference. Heat isolation, electrical insulation, and suppression of pressure wave in the tube were realized through a pitot tube filled with damping particles. Gas pressure, arc current and voltage around current zero were measured by the silicon piezoresistive pressure transducer and the current-zero measurement system, respectively. The influence of short-circuit current and ratio of mixtures on the pressure variations at nozzle throat and current-zero behaviours were analyzed. Mayr dynamic arc equation was used to predict the post-arc behaviors of SF₆-CF₄ arcs by varying rising rate of recovery voltage (RRRV) and current steepness at zero-crossing (di/dt). It is found that the gas pressure increment and critical RRRV tends to get weak as CF₄ is added to SF₆. Critical post-arc current of SF₆ and 50%SF₆-50%CF₄ are 0.74A and 0.96A, respectively. Critical RRRV of 50%SF₆-50%CF₄ are about 77% of that of SF₆, revealing a certain correlation between the critical RRRV and the pressure increment.