Effect of clipping pressure for low current duties in arc assist circuit breakers

Abstract

Arc assist interrupters are two stage interrupters having self blast volume (Thermal Volume) and Puffer Volume. In this type of interrupters, energy dissipated by the arc, during high current phase, is stored as potential energy in the gas. At current zero, gas flow created by the stored energy, sweeps the arc out of the gap between the arc contacts. The cool gas from the compression volume (puffer volume) is introduced in the thermal volume as well as between the arc contact gap for recovery of the gap dielectric strength. This will help to withstand against the applied transient recovery voltage (TRV) and complete the interruption successfully. Arc assist interrupter has two gas chambers, one which generates high pressure by using heat of the arc and other chamber generates high pressure by mechanical compression. Magnitude of short circuit current will decide the pressure developed inside the thermal chamber. For lower current duties, pressure developed by the arc during interruption is less so it is critical to clear the lower current duties for arc assist circuit breakers. This paper deals with variation of clipping pressure to generate the adequate pressure required for arc quenching for lower current duties. In this we have used 3 variations of clipping pressures as 5bar, 7bar and 10bar and results were analyzed. This paper discusses the effect of clipping pressure variation on pressure generation in compression chamber, Thermal Chamber and also density and temperature variation between contacts at current zero during interruption of arc.