Abstract
In the present paper we investigate the Ground Effect of small rod-rod air gaps, in connection to the Mirror Effect of rod-plate air gaps. The Ground Effect is 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). The Mirror Effect is valid in rod-plate air gaps when the plate's diameter is very big. The field distribution along the axis of the gaps is analyzed with the Finite Element Method. The maximum values of the field strength in the gap are recorded for the two different arrangements the one with one electrode grounded, and the other 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 geometry of the arrangement, and the electrode, chosen to be at earth potential (grounded). The Mirror Effect establishes equivalence between the rod-plate and rod-rod arrangements. It is resulted that the Ground Effect and the Mirror Effect influence the corona onset and the breakdown voltage of the air gaps analogically. It is intense in small air gaps, while the influence of the corona current appears in longer air gaps and overlaps the Ground Effect. The principle of action-reaction is valid.