Grounding plays a very important role in ensuring safe and reliable operation of power systems and protecting people and electrical equipment. The continuous increase in the voltage level and scale of power systems has resulted in the increasing strictness of the technical requirement for grounding devices. Grounding resistance is an important index to evaluate the effectiveness and safety of the grounding system.
The grounding resistance is usually rated at 10Ω for thunderbolt protection, and 1Ω or less than that at large scale substations.
The factors influencing the grounding resistance of the vertical electrode are the radius and length of the electrode, the soil resistivity and the embedding depth. It is essential for the design of the vertical grounding electrode to get a mathematical model of the grounding resistance that comprehensively reflects the influences of the factors on the grounding resistance of the vertical grounding electrode.
Many authors have published their research results for the mathematical modeling on the grounding resistance of vertical grounding electrodes, but they considered only the length and diameter of the vertical grounding electrode and the soil resistivity.
The length and diameter of the vertical electrode as well as the embedding depth affect the grounding resistance.
Kwon Hye Yong, a section head at the Faculty of Electrical Engineering, has obtained a mathematical model for the grounding resistance of a vertical electrode that accurately reflects the influence of embedding depth in a homogeneous soil, and verified its accuracy through computer simulation analysis and field measurements at different soil resistivity conditions.
The computational results by the proposed model agree with the results of computer simulation analysis and field measurements.
For more information, please refer to her paper “A Method for Grounding Resistance Calculation of the Vertical grounding electrode” in “Electric Power Systems Research” (SCI).
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