We have benchmarked our SafeGrid Earthing Software results for a 60 x 60 m grid against well-known software XGSLab™ and CDEGS™. We show that the results for grid resistance in multilayer soils up to 5 layers are virtually identical.

This article shows the effects of soil resistivity and thickness of layers on grid resistance for earthing systems in multilayer soils. Increasing the resistivity of soil layers tends to increase the grid resistance, no matter which soil layer that is. Increasing the thickness of any soil layer with high resistivity also increases grid resistance and if the soil layer thickness is increased for a low resistivity layer then the grid resistance will decrease. Software modelling is performed and the results are compared and shown to match well with those from CDEGS software.

The Annex H in IEEE Standard 80-2013 contains benchmark case results for comparing and evaluating software tools and methodologies used for the analysis of substation earthing. The results compare the simple equations from IEEE Std 80 with the results given by some of the commercially available software such as CDEGS, ETAP, SGW, SDWorkstation and WinIGS.

The effects of lightning strikes on earthing or protection systems designed to IEC 62305 can be modelled using an equivalent single frequency from 25kHz up to 1MHz which gives similar results to a time-domain approach. This article provides the frequency and current values to be used for modelling lightning.

Soil resistivity is one of the most critical factors affecting earthing and grounding system performance and safety. In cold climates, the top-soil layers may be frozen during the winter or spring seasons, and resistivity may increase to as high as 10,000 Ω.m in the frozen soil layers. This can give rise to significant touch voltage hazards during an earth fault.