Numerical analysis of electrical field surrounded the model HV electrode setups with paper insulation immersed in oil

Determination of potential and electrical field distribution in the vicinity of model electrode setups may be helpful in the deduction about the influence of paper insulation on HV electrode on the mechanism of initiation and propagation of electrical discharges in mineral oil. The attempt of confirmation of the hypothesis resulting from the previous experimental investigations, which pointed out that the source of “weak points” of paper-oil model electrode setup is oil, not the surface of metal or insulation wrapping, is presented in this paper. This hypothesis relies on the identity of times to discharge initiation measured in the same condition for insulated HV electrode and bare HV electrode having the same outer dimensions as the insulated one. These times and measurement condition were related to the well known the most stressed oil volume law. According to this law, the same oil volume may be statistically the source of the same number of “weak points” in the paper-oil insulation setup. Thus, for both model electrode setups (with bare and paper insulated HV electrode) having the same outer dimensions, the maximum electrical field stress may be also the same. Therefore, obtained, on the basis of the experimental works, identity of times to initiation seems to be explainable. Above described problem, at the stage of preliminary analysis, was verified using the numerical software based on the finite element method.