Extension of the empirical formula for pulsed electric strength of transformer oil

摘要

Discharges in liquid obey time effect, pressure effect and scale effect. Traditional formulas are usually applied in a narrow range to keep the formula form consistent with Martin's formula. In this paper, we have developed a new empirical formula for the electric strength of transformer oil depending on pulse duration, hydrostatic pressure and gap geometry in form Ebr = κeat-beff Pγ A-β d-ξ to be applied in a wider range. In this formula, the time dependent pressure effect is represented by constant y, which can be expressed as γ = ape-bpt-cpeff. Time effect, area effect and distance effect are represented by eat-beff, β and ξ, respectively. For transformer oil, κ=0.42, a=0.53, b=0.23, ap=0.14, bp=0.93, cp=0.41, β=0.1 and ξ=0.25±0.06, with Ebr, teff, F, A and d in MV/cm, μs, MPa, cm2 and cm, respectively.