Analysis Of The Effect Factors Of The Measurement Of Grounding Resistance

Grounding resistance is an important parameter of the Lightning Protection, and it can evaluate the efficacy and correctness of the the grounding system in Lightning Protection Standards. An exploring on how to scientifically and correctly measure the grounding resistance, as a research subject, has an important practical significance.At first the paper introduces the background and significance of measuring the grounding resistance, includes the traditional methods and some progress at home and abroad, and points out some problems at the existing measuring method.Because soil resistivity is the important influencing factor of measuring the grounding resistance, the paper introduces the measuring methods of soil resistivity, and deduces the formula of the Wenner method on measuring the soil resistivity. When the soil exists horizontal layering or vertical layering, it analyses the measurement errors by using the Wenner method and draws the relation curve about the soil resistivity, the test pile spacing, the soil layering. It deduces the formula about the electric field of midpoint current source in the soil vertical and horizontal layering.Then the paper introduces the measuring methods of grounding resistance and analyses the position in the three-electrode method. It calculates the error in different positions of voltage electrode. It concludes that the position of voltage electrode and electricity electrode can be interchangeable when voltage electrode is located at the voltage compensation position. It analyses the voltage compensation position by using the straight-line method and thirty degree method when the soil exists the horizontal layering. Through comparing with the GB/T 17949, there is some difference and questions. By using the straight-line method and thirty degree method, It calculates the relative error of the grounding resistance when d=5r and d=10r.At last, the paper introduces the mutual inductance, the underground metal, the resistance in the voltmeter, the skin effects the polarization effect, the physical characteristic in the measuring electrode, the jamming signal, etc. They can affect the measuring result of the grounding resistance.