Analytical Prediction of High Pressure SF6 Gas Breakdown Strength in a Spark Gap Switch

It is difficult to predict or measure breakdown strength of SF₆ gas, especially in high pressure range. It is even hard to find reference data of the high pressure SF₆ breakdown strength. We tried analytically to compute the breakdown strength of SF₆ gas above 3 bar-cm range in a spark gap switch. The computed result is compared with several published experimental data and showed good agreement for different geometries with a wide range of pd (pressure time gap distance) and field enhancement factor (FEF) to a great extent. For the computation, J.C. Martin´s modified field formula as well as Kuffel et al´s formula for breakdown in SF₆ gas is adopted. We will discuss the analytical prediction method of the high pressure SF₆ breakdown strength and the compared result with experimental data.