Fitting algorithm of transmission tower grounding resistance in vertically layered soil models

• A method to calculate tower grounding resistance easily yet accurately is proposed.
• The fitting functions are used to fit the grounding resistance of layered soil model.
• A fitting formula of tower grounding resistance for engineering is derived.

It could be quite complicate to calculate the accurate grounding resistance of transmission line towers in an vertically layered soil model, which could bring excessive time consumption and computation load to many engineering applications. In order to calculate the resistance fast and conveniently while keeping necessary accuracy, we propose an algorithm that uses the least squares curve fitting method and hyperbolic fitting functions to fit the resistivity and grounding resistance of layered soil model. An expression of the fitting function and the fitting formula of tower grounding resistance are derived theoretically according to application demands. We applied the algorithm to calculate a practical case and the result has error less than 10%.