Influence of bubble size and flow velocity on AC electrical breakdown characteristics of LN_2

摘要

To evaluate insulation design of high voltage for high T_c superconducting (HTS) power apparatus, the effect of bubble and electrode arrangements on the AC breakdown characteristics of LN_2 were investigated. Supposing that an outbreak of quench, the three electrode models were employed for breakdown voltage measurement in LN_2 with bubbles. Experimental results for various quench conditions revealed that the breakdown voltage of LN_2 with increasing the bubble size, flow velocity and electrode distance. Then, the relationship between the bubble conditions and the AC breakdown characteristics of LN_2 were clarified. Also, bubble movement phenomena were observed with an electrode model which consist of plane to cylindrical needle electrode immersed LN_2 for the simulation of the insulation environment in HTS pancake type coils and others of the quenching state.