The influence of the Ground Effect to the Corona Onset and the Breakdown Voltage of small rod-plate air gaps

摘要

The most determinant factors of the values of the corona onset and the breakdown voltages of an air gap arrangement are the distribution of the electric field, and the corona effects in the gap. The Polarity Effect affects the corona onset and mainly the breakdown voltage of the rod-plate air gaps. In the present paper we investigate the Ground Effect of small rod-plate air gaps, a phenomenon, which is observed due to the fact that in air gap arrangements one of the two electrodes is usually at earth potential (grounded). Values of the field strength in the gap are recorded for the three different arrangements with the rod or the plate grounded, either with symmetrical charging of the electrodes. The distribution of the field along the axis of the gap is strongly affected by the gap length, the rod's and the plate's diameter, and especially by the electrode chosen to be grounded. The Ground Effect affects the corona onset and the breakdown voltage of the rod-plate air gaps analogically. It is intense in small rod-plate air gaps, slightly affected by the Polarity Effect, while the influence of the corona current appears in longer air gaps and overlaps the Ground Effect. The principle of action-reaction is valid.