A new technique to Improve the dielectric strength of an multi-dielectric insulation system by applying the transverse electric field to main electric field

Abstract:
In this study, an attempt is made to improve withstand ability of the multi-dielectric medium by the
effect of an additional electric field in the transverse direction to the main applied electric field. H.V.
insulation system is choosed in this study is air-solid insulation system. In this study, two types of gaps
are used simultaneously : The first one is the main tested gap and the other is the transverse gap The
main tested gap consists of two parts :
Part I is air insulation and part II is solid insulation. The transverse field is applied to part I, i.e.; air gap
of the main tested gap. According to the results extracted from this work, the flashover voltage of the
dielectric medium II increases as the transverse voltage within the region I increases; whereas the
conduction current of the main tested gap decreases as the transverse voltage increases. Moreover, the
effect of transverse voltage increases as gap pressure decreases. Actually, the effect of transverse
voltage is much marked in low vacuum gaps than in atmospheric air gaps and compressed air gaps.
The improvement in flashover behaviors in the presence of a transverse electrical field illustrate a
marked dependence on the following: the item of pressure, the type of transverse applied electric field
(a.c or d.c) and the transverse field plane level. However, the improvement does not depend on the
specimen material. Moreover, it is worth mentioning that this improvement in the flashover behaviors
of solid dielectric in the region II is related fundamentally to the process of lowering electric stress in
the region I of the main tested gap.