Ground Fault Analysis and Risk Assessments for the High-Tech Industrial Plants Supplied by VHV Distribution System
| Autor: | Cheng-Nan Chung, 鍾政男 |
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| Rok vydání: | 2008 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 96 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. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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