Investigations on the Effect of the Nozzle Material on the Interruption Capability of a Medium Voltage Load Break Switch

Abstract

In the process of substituting sulphur hexafluoride in medium voltage load break switches by atmospheric gases, the inferior arc quenching capabilities of possible substitutes have to be compensated. By introducing a polymer nozzle into the switching gap of a load break switch, the interruption capability can be enhanced as the ablated nozzle material changes the composition of the arc plasma. In this contribution the interruption capability of a model load break switch is investigated using different nozzle materials. The results show a good interruption capability when using polypropylene and polyamide 6.6 for high blowing pressures. Polytetrafluorethylene shows good results across a wide blowing pressure range. Polylactide has the lowest interruption capability among the polymers in this work.

Impact of Ablation Based Self Blast Nozzles on Load Break Switch Current Interruption Performance

“…In figure 2C, the nozzle is represented in red. They are made from 40 mm PTFE cylinders, as this is a common nozzle material in ablation assisted switch gear [7]. In the nozzle, an 11 mm cylindrical channel is made where the 10 mm pin contact can move, this is the space where the arc is burning.…”

“…Test circuit used on the high voltage side of the high current breaker lab at NTNU on ablation assisted self-blast switchgear has used holes blowing right onto the arc centre or along the arc length [6,7]. This may not be the best way to cool the arc, as such, in this contribution, the positioning of these holes will be explored.…”