The article describes one method of calculating large earthing devices or a system of several interconnected earthing devices. In doing so, the assumption of equipotentiality of all points of the grounding device is rejected. The proposed method allows the analysis of various earthing problems, such as: research into the characteristics of large earthing devices, analysis of the mutual influence of several earthing devices, more precisely determining the danger of the presented potential, etc. Some examples of the application of a computer program based on the described method in analyzing large earthing devices, that is, earthing systems, are presented.