Electric fields in the transition region of sphere-gaps to parallel-plane gaps

The electrode gaps which results in to uniform electric fields are the most widely used gap configurations in assessing dielectric strength. In the present study simulation results of parallel plane electrode gap configurations with symmetrical and unsymmetrical supply are reported. When plane radius of plane electrode is reduced the plane electrode at its extreme case forms a sphere resulting in to sphere gap arrangement. Results in this transition region are reported. The charge simulation method (CSM) is used to compute electric fields; with errors in simulation being less than 0.06% (in potential). Simulation results indicate that as the plane radius increases the field uniformity increases. Non uniformity for a given plane radius depends on the gap spacing. For given gap spacing when the plane radius of the electrode is more than the gap spacing, improvement in uniformity are not significant The unsymmetrical supply results in higher field non-uniformity in the gap. The height of high voltage (H.V.) electrode above the ground plane (designated as parameter "A" in IS 1876-1961 for sphere gaps with vertical electrode arrangement) has shown negligible influence on the electric field distribution in the gap.