The dynamic measurement of surface charge distribution deposited from partial discharge in air by Pockels effect technique

Abstract

A recently developed electro-optical Pockels effect technique, which allows the dynamic measurement of surface charge distributions, is employed to observe the dynamic behaviour of a partial discharge in a point - dielectric gap. One period of an 8 kV ac voltage is applied to a needle electrode with gap spacings ranging from 0 to 7 mm. Different discharge behaviour and different deposited surface charge distribution patterns are observed for different point - dielectric gap spacings. The electrode gap spacings can be roughly divided into three regions, namely the surface discharge region, the transition region and the space discharge region. In the transition region, both surface discharges and space discharges which consist of a spark discharge and corona discharge are observed. The memory effect associated with the accumulated surface charges plays an important role in controlling the discharge behaviour. The surface charge field component may either suppress or enhance the local field near the point electrode depending on the phase of the applied voltage. `Back-discharges' are the typical result of the memory effect. Negative surface charge deposited from previous discharges can have a considerable influence on the propagation of the subsequent positive surface streamer channels depending on whether they develop in the surface discharge region or in the transition region.

Phase resolved cross-correlation spectroscopy on surface barrier discharges in air at atmospheric pressure

“…During the first MD the dielectric is positively charged. Similar phenomena are known from volume barrier discharges as well as different coplanar and SBD arrangements [10,[14][15][16][17][18]. The residual charges weaken the electric field locally and thus, the next breakdown will not occur at the same position as long as the electric field outside this zone is higher.…”

Development of Barrier Discharges: Operation Modes and Structure Formation

“…A positive space charge accumulates in front of the anode up to a level incepting the propagation of a cathode directed ionization front or streamer. Surface ionization due to detrapping, ion impact and photo effect or surface attachment of charge carriers may have a strong influence [38,39] which should be investigated in more detail. With increasing distance from the anode, the velocity decreases to 1.5×10 5 m/s at the cathode region.…”

Localization of electrical-insulation and partial-discharge failures of IGBT modules

“…7 and 8). The phase of the pulses can be explained by surface charges [15] produced in the discharge region (Fig. 9).…”