| Summary: | 碩士 === 國立成功大學 === 電機工程學系專班 === 94 === The safety of the human beings and equipment is the main objective of grounding protection. The ground resistance is judged whether the ground system is good in existing standard, but the ground resistance is not enough to judge safety in grounding, the questions of the earth surface potential, the step voltage and the touch voltage must be considered. Based on the basis of electromagnetic theory, this thesis analyze the variation of voltage, electric field and magnetic field while the fault current flows into the ground rod. The software of Finite Element Method COMSOL (FEMLAB) is used to analyze the variation of ground resistance, ground potential rise, step voltage, earth surface potential, earth surface electric field and magnetic field when the fault current flow into the ground rod and on the conditions of ground rod buried depth changed, soil resistivity changed, the ground rod buried in different resistivities of multi-layer soil or added ground resistance reduction agent. Thus, the effect of extraordinary potential and estimate ground design and safety in grounding can be developed.
The simulation results show that the ground rod bury to deepen, the step voltage decreases greatly. The location of the maximum step voltage follows the changes of ground rod buried depth. The deeper the ground rod bury, the farther the maximum step voltage locates. The ground resistance reduction agent can be decrease ground resistance. Due to the changes of the current distribution in the soil, the maximum earth surface potential and the maximum step voltage may be increase.
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