Research on new grounding technology of transmission line tower in Karst area

Resistivity of soil in Karst area is on the high side so that resistance of transmission line tower is difficult to fulfill the requirements of lightning protection. This paper mainly studies the calculation method of transmission line tower resistance in Karst area, and influences of Karst caves to resistance. Considering Karst topographical features, according to the similarity of constant current field and electrostatic field, the model of soil and the physical model of grounding device in frequency current are built based on current distribution, electromagnetic fields, grounding and soil stricter analysis(CDEGS), the model of soil and the physical model of grounding device in impulse current are built based on COMSOL Multi-physics, frequency resistance and impulse resistance are calculated respectively. Finally, frequency and impulse simulation experiments are carried out in high voltage test platform to verify the models, based on dimensional similarity principle. The results show that the resistances calculated by models and resistances obtained by experiments match well. What is more, factors such as cavity size, distance between cavity and grounding device, are founded to have significant influence on resistance.