A new method of measuring earth resistance applicable to mutually bonded earth electrode systems

In NTT's telecommunication buildings, it has been difficult to measure the earth resistance of telecommunication power system's grounding after services have started because the grounding conductor cannot be removed from the earth electrode. Recently, earth electrodes of most of the buildings have been mutually bonded to protect the facilities against lightning surges, so it has become difficult to measure the earth resistance of the individual earth electrodes. Furthermore, the measurement itself has become difficult using the traditional earth tester, which uses assistant electrodes, since the land around most telecommunication buildings has been paved with asphalt or concrete. The authors have developed a new method of measuring the earth resistance of each of the mutually bonded electrodes under these circumstances.