DC Current Limitation Principle Using a Helical Arc Arrangement

The expansion of a helical arc confined between polymeric helical blades is governed by both electromagnetic and aerodynamic forces. These arise due to complex interactions between the individual arc turns, arc helical blade interactions, and surrounding media. These interactions can be exploited to control the rate of expansion. During this expansion stage, there is a substantial increase in arc voltage which, in low voltage (LV) systems, can limit the current, thereby potentially approaching current interruption provided that the arc quenching conditions are suitable. In this investigation, current limiting properties of different combinations and sizes of helical blades (metal and polymer) were studied experimentally. Marginal improvement in current-limiting properties was found upon substituting (two) outer polymeric blades with copper. Increasing the blade count was also beneficial. Blade size was, however, the most significant factor for enhancing arc control and current limitation-three large polymer blades outperforming all smaller blades-even with less blade area.