Electrical Breakdown in Gaseous Nitrogen at Cryogenic Temperature with a Heated Tape Electrode

With the objective to better understand and design the electrical insulation of resistive superconducting fault current limiters (r-SCFCL), breakdown experiments were performed in liquid (LN2), and gaseous (LN2) nitrogen. Conditions relevant to the extreme case of severe boiling, occurring during superconducting/resistive transition, were chosen. A tape-shaped electrode rapidly heated by impulse Joule effect is used to closely represent the specific conditions occurring during the transition. Comparisons with previous experiments carried out in LN2 show that the reduction of breakdown voltage during transition results from the replacement of LN2 by GN(2), and from heating of GN(2). Breakdown voltages in GN(2) with divergent tape-plane geometry can be modelled using the streamer criterion.