Research On Measurement Method And Experiment Of Tower Grounding Resistance

Tower grounding resistance is the main parameter to judge the ground performance, which directly affect the safety of the power system and stability of the electrical equipment, thus accurate tower grounding resistance measurement is of great engineering significance. At present, the main problems of tower grounding measurements are: imprecise electrode arrangement caused by unknown tower grounding body, which affects the accuracy; low efficiency when measuring without grounding lead connected; big error by injecting single frequency current when connecting grounding lead. Hence, this paper put forward a tower grounding accurate measurement, the main works are as follows:(1)Through the established model of tower grounding body and analysis of the distribution of the magnetic induction intensity caused by injected current, a judgment method of grounding body buried position was put forward, Then the theoretical analysis of the current frequency and soil resistivity affecting the method was given; what’s more, the simulation of the distribution of the surface magnetic induction intensity, the current distribution of grounding body and the influence of injected current and soil resistivity are given, The result shows that when the injected current frequency f ?20kHz and soli resistivity ? ?200?.m, the surface magnetic induction value decreased, but measure it of 1m around the tower can effectively judge the position of grounding body and achieve the accurate electrode arrangement.(2)equivalent circuit model of tower grounding resistance measurement with grounding lead connected was established, the grounding impedance changing with injected frequency was analyzed and an accurate condition was given, thus the frequency selective tower grounding resistance method was put forward. What’s more, the influence of grounding resistance, equivalent induction of grounding body and induction of grounding wire were analyzed through simulation model. The result shows that considering soil resistivity, the method can inject different range of current within 1 ~ 12 k Hz and select the best frequency point, In addition, the three parameters influence little to the measurement results, the method can measure accurately after electrode arrangements.(3) Experiment device of the tower grounding resistance measurement was constructed and the output current frequency range is 1 ~ 10 kHz, then the experiment platform of tower grounding body buried position judgment was constructed. e laboratory experiment and field experiment were carried to verify the feasibility of the method to judge the buried grounding body position. The result shows that the method can judge the grounding body position and of a good feasibility.(4) Based on the experiment devices, frequency selective tower grounding measurement laboratory experiment and field experiment were carried, The results verify the reliability of the frequency selective method compared with results measured by common methods(three electrodes method, clamp-on method and high frequency parallel method) after accurate electrodes arrangement.