Experimental investigations on power frequency electrical breakdown characteristics of liquid nitrogen for HTS power devices

The discovery of high temperature superconductors (HTS) led to a breakthrough in the development of superconducting power equipments. Now, in addition to liquid helium, other cryogens like helium gas, neon gas, liquid nitrogen (LN₂) etc. can also be used for cryo- cooling purposes. Among all the cryogens, liquid nitrogen is most abundantly available with the least cost. The liquid nitrogen serves as a cryogen and also acts as insulation for high temperature superconducting power equipments working at high voltages. Hence, it becomes essential to characterize the power frequency breakdown strength of LN₂for designing the HTS based power devices. In the present work, to evaluate the breakdown strength of LN₂ at power frequency (50 Hz), a test setup has been designed and developed for characterizing the power frequency breakdown strength of LN₂ at atmospheric pressure using standard test procedures and the results are presented.