IEEE
IEEE 81-2025 is a guide published by the Institute of Electrical and Electronics Engineers on measuring earth resistivity, the impedance of grounding systems and earth surface potentials. It explains the methods, instruments and precautions used to characterize the soil and to verify how a grounding system performs once it is installed.
Editions cited: IEEE 81-2025
The guide serves anyone who designs, installs or verifies a grounding system, from substations and generating plants to industrial facilities, towers and telecommunications sites. It describes how soil resistivity is measured and interpreted, how the resistance or impedance of a ground electrode or grid is obtained, and how step and touch potentials are assessed. It stresses the limits of each method, including interference from buried metallic structures, stray currents, test lead spacing and the effect of seasonal soil moisture. It also treats continuity checks within a grounding network. Design engineers, commissioning teams, utility field crews and testing firms use it to choose a measurement method that suits the site and to judge whether the result can be trusted. The pages in this encyclopedia that cite IEEE 81-2025 explain ground electrode resistance and point to point continuity testing in general terms and point the reader to the guide for governing methods.