An experimental review of different methods for measuring the grounding resistance of OHTL towers

Before commissioning a new overhead transmission line tower, it is imperative to conduct an initial electrical test on its grounding system. This test ensures that the grounding system is effective in protecting against dangerous touch voltages and maintaining electrical safety. By guaranteeing a low grounding resistance, the likelihood of insulator backflashovers from lightning strikes can be reduced, and dangerous touch voltages on the tower can be prevented. There have been surprisingly high deviations observed during receptive grounding resistance measurements of aged towers using different measurement equipment. Investigations revealed that the often-used passive measuring technique at the operation frequency of 50 Hz is susceptible to interferences caused by the magnetic field of power lines. Comparisons were made among three different measuring methods using two different devices on various towers with both good and poor grounding conditions. The results indicated that only one measurement method with each device could provide reliable results This paper demonstrates that measurements conducted at higher frequencies can yield more reliable results, as they are less likely to be affected by the magnetic field of the power lines. Each measurement device has its own hardware and software limitations, which can lead to incorrect measurements.