Surface flashover along polymeric rods partially immersed in LN2

Surface flashover phenomena along polymeric rods partially immersed in liquid nitrogen were investigated between parallel electrodes and compared with those fully immersed in liquid nitrogen and those in gaseous nitrogen at cryogenic temperature. It was shown that ac flashover voltage along polymeric rods half immersed in liquid nitrogen was almost the same as that of fully immersed rods when the length of the rod was <10 mm. In the case of 20 mm long rods however, ac flashover voltage was close to that obtained in gaseous nitrogen at cryogenic temperature. Contrary to ac flashover, regardless of the length of a rod to 20 mm, lightning impulse flashover voltage along the rod partially immersed in liquid nitrogen lies between that in liquid nitrogen and that in cryogenic gaseous nitrogen