Can an entire substation grid and associated ground rods be tested with a clamp-on resistance tester?

Testing an entire substation grid and associated ground rods with a clamp-on resistance tester is not recommended due to several reasons. Clamp-on resistance testers are designed for measuring the resistance of grounding systems under specific conditions, usually for smaller installations or individual grounding rods.

In the context of a substation, which involves complex networks and high currents, using such a device might not yield accurate results because these testers are typically not designed to handle the extensive setup and potential electromagnetic interference present in a substation environment. Moreover, the safety risks associated with working on electrical systems in substations are significant, and the clamp-on method does not provide a comprehensive assessment of the grounding system's effectiveness when dealing with multiple grounding points within a larger grid.

Additionally, while it is possible to measure grounding resistance with a dampened clamp-on tester under ideal conditions, the complexity and potential for false readings in a substation context makes it less reliable and, therefore, not the preferred method for ensuring safety and operational integrity.