Short-Circuit Current Interruption in Liquid Nitrogen Environment

In combination with high temperature superconductive (HTS) equipment (e.g. current limiters) or in HTS subnets, which constitute a possible option for increasing the overall efficiency of electrical power distribution systems, only vacuum interrupters can be used directly in the liquid nitrogen environment. This would, however, be desirable for economic reasons. Circuit breakers and switches, respectively, are necessary to configure the network, and they should preferably be installed in the cold environment in order to avoid unnecessary transitions between the cold and the warm environment. In this investigation two commercially available vacuum interrupter (VI) types from two different manufacturers were investigated at ambient temperature and in liquid nitrogen. The breaking current was increased until an insulation of the transient recovery voltage (TRV) was not possible anymore. All tests were performed on two different types of vacuum interrupters, but installed in the same switchgear. The short circuit performance did not show any significant change in the liquid nitrogen environment. This paper also offers an outline of future tests needed to validate the use of VIs at low temperatures.