Arcing time analysis of liquid nitrogen with respect to electrodes geometry

摘要

Liquid Nitrogen Insulated metal enclosed Switchgear (LNIS) is an alternative to the conventionally used Gas Insulated Switchgear (GIS), so all the components of GIS must be considered for LNIS as well. The principle research is however required to examine the behavior of arc plasma in Liquid Nitrogen (LN₂). Until now, no one has ever investigated the arcing time in LN₂. The objective of this work was to investigate the arcing time of LN₂ and compare the results with open air conditions using different electrodes geometry. Experiments were conducted on different DC voltage levels and their arcing times were measured. Three different kinds of electrode geometries, namely: Rod-Rod, Plane-Plane and Sphere-Sphere were tested. The electrode gap was taken to be 30 mm for all the cases. Stainless Used Steel (SUS) made electrodes were employed. The results show that LN₂ extinguishes arc in one third of the time required by the open air insulation when SUS made electrodes are used. Results in most cases also revealed that, the Sphere-Sphere type electrode geometry has the shortest arcing time while Rod-Rod is the second best choice and Plane-Plane type stand last in the evaluation. It is learned from the results that LN₂ is a better choice than air insulation in terms of arc quenching and could possibly be an efficient alternative to the Sulphur Hexafluoride (SF₆) gas.