| Summary: | 碩士 === 中原大學 === 電機工程研究所 === 93 === Abstract
In this thesis, the ground fault characteristics of closed-loop very high voltage(VHV) underground distribution system (VHV underground loop) are studied which includes the ground potential rises(GPR), step and touch voltages on the utility and customer substation grounding systems and the current distributions on the cable shielding conductors. The grounding conditions of cable shielding conductors are considered which includes common grounding or individual grounding for the cables in the man-holes, the variation of grounding resistances and the on or off states of the surge arresters in the cable-cover-protection unit(CCPU). For a VHV underground loop, the grounding grids in utility and customer substation and the grounding electrodes in the man-holes are connected together via cable shielding conductors and interconnected conductors (auxiliary grounding wires). So, the ground fault current of any one of customer will flow pass through all other customers’ grounding systems and thus produce GPR, step and touch voltages and large current on shielding conductors or flow into surge arresters. These problems have been found from the study results and their affections are also assessed, and this study provide useful data for improving the performances of VHV underground loop.
Keyword: very high voltage underground loop, cable grounding
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