| Power system operation experience has shown that, the impulse grounding resistance of transmission lines tower grounding electrode directly affects the lightning protection performance of power transmission lines, and the impulse grounding resistance are closely related to the impulse characteristics of grounding electrode. It is very important to carry out experimental research on the impulse characteristics and resistance reduction effect of grounding electrode for the safety and reliability operation of the power system and the personal safety of the staff.Understanding the impulse characteristics of the soil is a key way to investigate the soil spark discharge phenomenon around transmission line tower grounding electrode under the impact of lightning current. It is also the basis of lightning protection of power transmission projects. Because soil spark discharge would obviously reduce the impulse grounding resistance of grounding electrode and the overvoltage of electrical equipment. At present, the shortcomings of the research on impulse characteristics of the soil are as follows:Study on the characteristics of the soil ionization was more than the characteristics of the soil after breakdown. Therefore, It is necessary to study on the impulse characteristics of the soil through experimental, It can be provided the basic theory for accurately establishing the transient calculation model of the grounding device under impact of the current. The grounding module is a new physical resistance reduction technology product of grounding resistance reduction measures of transmission line tower grounding electrode, In recent years, It have been widely studied and applied on the lightning protection project of international transmission lines But the grounding module which could effectively reduce the impact of grounding resistance was lack of validation of the experimental data, The performance of reducing grounding resistance is also lack of a more scientific analysis, There was blindness in use. It is necessary to study on the impulse characteristics of the grounding module through experimental, It could be provided a reference to the application of the actual ground projects.Based on the analysis of the literatures on experimental study and theoretical analysis on the impulse characteristics of grounding electrode, in this paper, experiment is proposed to analyze the impulse characteristics of the soil and grounding resistance reduction effect of grounding module, The main conclusions obtained in this paper are: Soil breakdown phenomenon would occur under the impact of the current, The impact grounding resistance was found to decrease with increasing current both before and after the breakdown. The time delay to breakdown TD was found to decrease with increasing moisture content, and increase with decreasing breakdown voltage, it also increased with the increasing front time of wave and the decreasing size of the ground electrode, And the negative polarity TD was higher than that of positive polarity. when the soil moisture content was very low, The critical impulse breakdown voltage was found to decrease with increasing moisture content, The critical breakdown electric field was also the same, And it was obviously lower than air30kV/cm. the current scattering effect of cylindrical grounding module was better than rectangular grounding module under different impulse current, the greater impulse current with the more obvious of the current scattering effect; The increase of grounding module current scattering area would increase its resistance reduction effect, but this effect was saturated trend. The greater of the soil resistivity, the more obvious of the resistance reduction effect, The resistance reduction effect of graphite type grounding module could be compared to the traditional metal grounding body, and had a greater potential applications. The resistance reduction rate of grounding module had nothing to do with the soil resistivity. |
PDF Full Text Request