Breakdown strength criteria of a spark gap switch in high pressure SF6 gas for pulsed power

It is an endeavor to develop switching technology for the breakdown reliability and reproducibility at extremely high voltage. The key objective of the endeavor is to derive breakdown criteria for use in high voltage design by which high pressure SF₆ breakdown strength in non-uniform field can be computed. For the computation of the breakdown criteria, J.C. Martin´s electric field strength of non-uniform electrode gap in air and Kuffel et al´s electric field strength of uniform electrode gap in high pressure SF₆ gas are adopted. The validity of the computed result has been ascertained with several experimental data from different investigators. In house, a spark gap has been designed and constructed at PAL (Pohang Accelerator Laboratory) with particular intension of developing a high pulsed power source. Breakdown voltage tests have demonstrated the functioning of the spark gap switch as intended up to 9bars of SF₆. In parallel, Field modeling has been performed to verify the appropriate shape of the highly stressed insulator and electrodes design in the spark gap. The final goal is to develop the switch technology for scaling to larger system.