Reduction of the fault current passing through the grounding system of an HV substation supplied by cable line

The paper presents an original analytical procedure developed for the determination of the part of ground fault current dissipated through the substation grounding system (electrode) into the surrounding earth in the cases when a specific measure has been taken to reduce it. The practical realization of this measure is simple and consists of burying one bare copper wire of a sufficient length together with the feeding cable line. The presented method enables a quick, and, for practical purposes reasonably accurate determination of the copper wire length providing the required safety conditions in the considered HV distribution substation and its vicinity. The developed analytical procedure is simplified by introducing an equivalent neutral conductor substituting all three cable line metal sheaths as well as all surrounding metal installations. The presented quantitative analysis shows that the effects achieved by this measure are significant.