Quick calculation of the grounding resistance of a typical 110 kV transmission line tower grounding system

•Grounding system resistance of a typical 110 kV transmission line tower was analysed.•Finite Element Method (FEM) and numerical analysis of the obtained results were used.•Formula for a quick calculating the analysed grounding system resistance was derived.•Improved formula for calculating the square loop grounding resistance is proposed.•Comparison with the FEM results showed very high accuracy of the derived formulas.

A general practical method, based on the Finite Element Method modelling and a numerical analysis of the obtained results, was applied for the calculation of the grounding resistance of a complex grounding system frequently used for typical 110 kV transmission line towers. An approximate formula for a practical evaluation of such a grounding system resistance, valid for the ranges of input parameters used in the Serbian transmission power system, is proposed. A new, more accurate formula for calculating the square loop grounding resistance is also given. The proposed method for generating approximate formulas intended for fast grounding resistance calculations is general and, therefore, can be applied to any type of complex grounding systems.