54 www.megger.comThe first step is to measure the resistance (RT) of the entire system using a typical fall-of-potential configuration. In this example, the reading for RT is 1.9 Ω.Step two involves measuring the total current (IT) being injected into the system from C1. For this example, IT is 9.00 mA. The next step is to measure the amount of current (IU) flowing to the service. In this case, IU is 5.00 mA. With these measurements, the voltage drop from the selected volume of soil to the point of the P2 can be determined as follows:V = IT x RT V = 0.009 A x 1.9 ΩV = 0.017 VThe current through the ground electrode (IG) can also be determined.IG = IT – IUIG = 9.00 mA – 5.00 mAIG = 4.00 mAFig 26: Leakage current measurements
