Experimental Study on Paschen Tests of ITER Current Lead Insulation

An experimental Paschen test setup has been established to analyze the quality of ITER current lead (CL) insulation and extend the research on Paschen's law under various conditions. Insulation problems can destroy a machine if a Paschen discharge is triggered by an insulation defect that is caused by faulty manufacturing, electromagnetic force, and thermal stress load with a certain degree of vacuum helium or pipe leakage. The results show that the CL insulation mock-up worked well under normal temperature and pressure. Besides, the mock-up also worked well in helium conditions and at 80 K temperature at di®erent pressures. One area of CL insulation was severely destroyed when the 80 K test was conducted after 5 thermal cycles, resulting in Paschen discharge phenomenon. The breakdown voltage is maintained at a relatively low level under di®erent pressure conditions; the change of breakdown voltage was mainly due to the change of pressure, and such change was in line with the Paschen law.