- 學位論文
特高壓供電科技廠接地故障分析及其風險評估
Ground Fault Analysis and Risk Assessments for the High-Tech Industrial Plants Supplied by VHV Distribution System
摘要
本研究主要分析特高壓(161kV)科技廠發生之接地故障特性，首先應用電磁暫態分析軟體(EMTP/ATP)建構電路模型，模型涵蓋有特高壓變電站等效模型、主變壓器、高壓電纜、高壓變壓器、下游系統負載以及各種設備接地線等。並且使用所建構之模型進行分析單相接地故障之暫態與穩態特性，其中故障位置分別為主變一次側(161kV側)、主變二次側(高壓22.8kV匯流排)及下游高壓變壓器一次側(22.8kV側)等三種情況，並考慮滿載、半載、無載等三種負載情形，以及特高壓電源端回流導體之影響。此外，由ATP軟體模擬分析獲得接地至地網之所有注入電流值，再應用接地系統分析軟體(CDEGS)來模擬地網電磁暫態及穩態特性包括地電位昇(GPR)、地表電位、接觸電壓、步間電壓、導體電流及地表電磁場之分佈狀況，其中各地網間互連之情形亦加以比較差異，藉由上述分析結果，最後將評估可能發生之風險包括對於人員與設備所受的影響，在本文中模擬得到的數據發現，主變二次側中性點電壓及下游設備之地電位昇可達數kV級，可能傷害到設備本體。而主地網電壓及電流亦可能威脅維護人員的安全及干擾敏感設備，應列為防護的重點。
並列摘要
This thesis is to the characteristics of single-phase ground faults in the high-tech plaints supplied by 161kV power. The circuit model is first constructed by using the electromagnetic transient program/alternative transient program (EMTP/ATP) in which the very high voltage(VHV) substations, main transformers, high voltage cables, down-stream system loads and each equipment grounding lines are considered. The model is used to analyze the characteristics of transient state and steady state of single-phase ground fault. Three fault points, namely, the primary of main transformer, high voltage bus and the primary of a down-stream high voltage transformer are analyzed. The load conditions, including full load, half load and no load, respectively. Both fault cases of with and without a return conductor at VHV source are analyzed for comparing the performance of return conductor. Based on the simulation results, the fault currents injected into grounding system at fault points are obtained and the electromagnetic characteristics values of ground grids are further analysis. Finally, a software package for grounding system analysis, namely, Current Distribution Electromagnetic Grounding and Soil Structure Analysis (CDEGS) are used, from which we can find the distribution of ground potential rise (GPR), potential on the ground surface, touch voltage, step voltage, conductor current and electromagnetic field (EMF) on the ground surface. All the electromagnetic characteristics of grounding system for both case of the with and without interconnetion between main ground grid and down-stream ground grid are analyzed and compared. Then based on the above analysis results, the affections on personnel, equipments and systems are evaluated. The study results had shown that the GPR will rise to several thousand volts on neutral point of secondary main transformer and down-stream system loads due to 161kV ground fault, which may damage to equipment itself. The voltages and currents on main ground grid may threaten personnel and interfere sensitive equipments. The associated data from this study is useful for further survey on risk evaluations.