Effect of Backfill on the Performance of Substation Grounding Systems

The effect of backfill on the performance of the grounding system of a substation is studied in this paper. The backfill is simply the replacement of the existing soil surrounding the grounding grid with a different soil. When the backfill soil resistivity is higher than the original soil resistivity, the touch voltage is higher compared with the case where no backfill is used; the step voltage can also be slightly higher. When the backfill soil resistivity is lower than the original soil resistivity, the touch voltage is lower compared with the case where no backfill is used but the step voltage is significantly higher. An approximate method for modeling the backfill in a multilayer soil is also presented.