Breakdown behaviour of nonuniform arrangements in air and SF6 using oscillating lightning impulse voltage

The breakdown behaviour of model arrangements (rod to plane, sphere to plane) and natural size arrangements (ring to rod, coaxial cylinders) was studied using oscillating lightning impulse voltage and lightning impulse voltage in air and SF6. Using a simplified equivalent circuit, the voltage curve and the values of the circuit elements can be calculated. At the model arrangement as well as at a natural size arrangement breakdowns in air occured below the impulse withstand voltage Ud0 at both polarities in SF6 only by negative polarity at the natural size arrangement.