AC Current Interruption Characteristics of Liquid Nitrogen

There is an increasing tendency to integrate several High-temperature superconducting equipment into a network. Along with it is the increasing demand for cryogenic power switches that could work in the liquid nitrogen (LN
₂
) to reduce temperature transfer areas. However, none of the current AC arc extinguishing mediums could work reliably in the LN
₂
. As the insulation and cooling medium of the HTS equipment, LN
₂
can be a potential arc extinguishing medium due to its strong cooling effect. However, the AC interruption performance of LN
₂
is unknown up to now. The objective of this paper is to obtain the AC interruption performance of the LN
₂
. A free-burning type and a magnetic blowout type LN
₂
switch are tested, respectively. Current ranging from 1 kA to 6.3 kA is conducted. Heat loss of the arcing process is also calculated. Experimental results show that a 2700 A AC is successfully interrupted by the free burning type switch at a 10 mm gap. The increase of the contact gap leads to slight growth in current interruption ability. Meanwhile, the magnetic blowout type can interrupt an AC higher than 6300 A. Based on the high interrupting properties of LN
₂
, a potential application in novel environmentally friendly switchgear is proposed. The LN
₂
switch in the switchgear can switch the closed-loop current that could be typically more than 50% of the continuous current. Meanwhile, the heat loss generated during the arcing process will not add an extra burden to the cooling system of the switchgear.