本論文首先討論大地阻抗量測原理與技術，接著為變電所接地系統之介紹，再以實際在台電公司台南變電所進行量測草地與碎石二種不同地質，以及接地電極不同埋入深度之量測值，透過計算分析來探討地表層舖設草地或碎石之好壞及接地電極不同埋入深度之差異；最後對變電所接地系統地表層舖設之不同材質，提出建議，並針對地表層舖設材質及厚度與人體最大容許步間及接觸電壓之關係，提出安全與效益評估。 Electrical engineers are concerned about the relationship between earthing systems and safety of workmen and equipments. Those who work for substations, power stations and transmission lines also have to take the performance of protection into their consideration. An earthing - mesh in a bulk grid of power system could be vulnerable owing to a lightening strike or an earth-fault occurred accidentally to the system . Due to the current, induced by a lightening strike or a fault , flows into the mesh , a potential rise and an influx of circumambient current could induce a major fault .In order to maintain a safe and stable power supply system and to protect workmen and equipments form being damaged.
This thesis would like to pay more attention on the issue. Firstly , the principle and techniques of the measurement of ground impedance are discussed in this thesis. Then it introduces the current condition of earthing system in substations. Furthermore ,we prompt to measure the ground impedance in Tainan substation based on grass ground and gravel ground respectively. The different depth of electrodes punched into the ground are also considered. Finally, by evaluating and analyzing the different results of measurements, we thus suggest a better selection to the cover layer of switchyard in substation. To assess the maximum allowance between step voltage and touch voltage on human body which is related to the different materials and depth layed on the ground of substations are also discussed in this thesis.