To meet the requirement for evaluating the surface insulation performance of cryogenic components such as high-temperature superconducting power transmission terminals, a cryogenic gaseous-nitrogen pulsed flashover test system is developed. Unlike conventional liquid nitrogen immersion tests, this system cools specimens via conductive heat transfer from a cold stage. Because an insulating layer is required between the specimen and the metallic cold stage for high-voltage testing, additional thermal resistance causes a noticeable temperature lag. Accordingly, particular attention is paid to the temperature deviation between the cold stage and the actual specimen surface, as well as to its calibration. Experimental results show that when the cold-stage temperature drops to approximately -100℃, the specimen surface temperature remains around 10℃ higher. A calibration relationship between the cold-stage and the specimen surface temperature is established. Combined with a COMSOL heat transfer model, the temperature distribution as well as the mechanism underlying the temperature difference, is analyzed. Finally, surface flashover tests on a typical epoxy insulation material produce stable flashover-voltage waveforms, confirming the feasibility of the system and calibration method. The developed system provide a basis for accurate electrical characterization of polymer insulating under low-temperature gaseous environments.

cryogenic gaseous-nitrogen,pulsed flashover test system,surface flashover,temperature calibration,polymer insulation