Comparison and Analysis of Grounding Impedance Measurement for Power Plant Grounding Device

Abstract:
Grounding Impedance is a key parameter in the field of lightning protection for power plant. From 2017 to 2020, the grounding impedance of a power plant in Ma'anshan was measured by straight-line method, angle method and reverse-direction method respectively, and comparation is made with simulation result by using CDEGS(Current Distribution, Electromagnetic Fields, Grounding and Soil Structure Analysis). The results show that measured results by using the straight-line method are similar to the simulation result. There is no obvious correlation between grounding impedance and current intensity, but significant positive correlation between grounding impedance and current frequency is ex-isted. When the angle is close to theoretical value of 28.95 deg, measured results by using angle method is close to other methods and error between angle method and simulation value is less than 5%. When the reverse-direction method is used and the current pole position is fixed, the grounding impedance increases with the increase of the distance between the potential pole and grounding device, and is close to the theoretical simulation value. The ratio of the imaginary part to the total impedance value shows a decreasing trend with the increase of the distance between the potential pole and grounding device, indicating that the reverse-direction method can effectively reduce the inductive component gener-ated by the mutual inductance between the potential and current wiring.