Initiation of discharges in the setup of paper insulated electrodes in oil

The article presents the problem of assessing the phenomena of electrical discharge initiation at high voltage, in the vicinity of paper insulated electrode in technical purity mineral oil. This problem was considered on the basis of results of experimental studies, which indicated that the supposed source of initiation sites in paper-oil insulation system are the weak points included in oil bath. Such conclusion resulted mainly from the measured and statistically analyzed times to initiation, whose average values in the case of electrode with insulation wrapping and without it were the same. Equality of average values were additionally confirmed using advanced statistical tool like analysis of variance. From the other hand, confirmation of founded hypothesis was obtained thanks to the 3D simulation of electrical field distribution in the electrode models used previously in experimental works. Obtaining practically identical maximum values of electrical field stress indicates on accuracy of the hypothesis seeing in the oil the sources of weak points and connects it with the most stressed oil volume law.