- 學位論文
考慮人孔接地條件探討特高壓地下環路接地系統之接地故障特性
A study on the Ground Fault Characteristics of Grounding System of Closed-Loop VHV Underground System Considering Grounding Conditions in the Man Hole
摘要
摘 要 本論文探討特高壓(161kV)地下環路供電系統的接地故障特性，包括在變電所、各用戶及管溝人孔處的地電位昇、步間電壓、接觸電壓以及電纜遮蔽層導體之電流分佈，其中將考慮電纜遮蔽層的接地條件，包括在人孔內兩邊電纜的接地是共同接地或單獨接地，接地電阻的變化、電纜被覆保護裝置(CCPU)之避雷器導通與否。由於整個環路的接地系統包括變電所及各用戶地網及人孔接地棒，皆藉由電纜遮蔽層導體及互連導體(輔助接地線)緊密互連，因此，任何一家用戶發生接地故障，故障電流將會流經所有用戶的接地系統，各用戶都會面臨地電位昇、步間電壓及接觸電壓對人員與設備的威脅，以及大電流對遮蔽層導體及避雷器之威脅，這些都經由本文的分析及評估得到證實，而本研究所獲得之數據可供改善環路規劃設計之參考。 關鍵字: 特高壓地下環路、電纜接地
關鍵字
地下環路並列摘要
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