Phase-to-phase insulation part I: Generalized effects of stress parameters and gap geometry

The parameters determining the response of phase-to-phase insulation are the amplitudes Vn(negative) and Vp(positive) of the two voltage components to the ground, their shape and the relative displacement Δt of their crests. In the present paper, the effects of Δt and of the ratio α = Vn/(Vn+ Vp) on the virtual total breakdown voltage Vn+ Vpare investigated. An attempt is made to derive an analytical expression for the combined effect of α, Δt and the polarity of the two components. Recommendations are offered as to the required geometrical arrangement for performing phase-to-phase tests as well as to the presentation of their results.