特高壓地下環路供電系統之接地系統接地故障特性研究

A Study on the Ground Fault Characteristics of Grounding Systems of Very High Voltage Underground System with Loop Structure

曾世翰(Shih-Han Tseng)

指導教授 ： 周至如

中原大學/工學院/電機工程研究所/碩士(2004年)

https://doi.org/10.6840/cycu200400194

摘要

中文摘要
電力公司通常以特高壓(例如161KV或69KV)供電給大用戶，若採用地下電纜供電，則其饋線以環路架構為主，簡稱為『地下環路』，雖然地下環路供電有很多好處，但仍有一些潛在危機可能發生，其中接地故障對系統的破壞很大，且發生機率很高，有必要加以探討以減少其傷害，為此，本研究探討典型的特高壓(161KV)地下環路的接地故障特性，針對每一家用戶發生接地故障時整個地下環路系統的地電位昇(GPR)分佈，及各用戶接地系統的地電位昇、步間電壓、接觸電壓、地表電位及電磁場的分佈進行分析並評估對人員與設備的影響。為了進行這些分析，本文首先建立地下環路的接地網路模型，此模型考慮電纜遮蔽層導體與遮蔽層導體之互感，並進一步用『解耦法』以修飾接地網路模型以方便於分析故障電流分佈。為計算用戶內部接地系統的特性分析，本文應用接地系統電磁分析軟體『CDEGS』做各項分析。分析結果顯示特高壓地下環路供電系統發生接地故障時，各接地點地電位昇可達數千伏，亦有很高的接觸電壓，對人員與設備會造成傷害，同時亦發現未發生接地故障的用戶亦有高的GPR，這種危險的現象稱為『接地故障轉移』，這使得未故障的用戶如同發生接地故障而受到傷害或停電，為了減少接地故障轉移的傷害，本文提出改善方法，研究所得的資訊亦有助於改善地下環路供電的性能。

關鍵字

地下環路 ； 接地故障轉移 ； 地表面電位 ； 接觸電壓 ； 步間電壓 ； 地電位昇

並列摘要

Abstract
The utilities usually supply large consumers with very high voltage (VHV) power (e.g.161kV or 69kV powers) If the VHV feeders are underground cables, the feeder circuits are constructed with loop scheme which are called underground loops. Although the underground loop has many advantage, some hiding risks may be happened where the ground fault is one of the most risks to destroy the system and with higher probability. For preventing the damages from ground fault, the characteristics of ground fault occurred at each consumer fed by underground loop are investigated in this thesis, where the ground potential and electromagnetic field distributions are analyzed for evaluating the affections on personnel and equipments. The grounding network model of underground loop is first constructed by considering the shielding conductors and the grounding resistances of their grounding points, the impedances of interconnected conductors, the grounding resistance of each consumer grounding system and the mutual inductances between the phase grounding system and shielding conductors of underground cables. The grounding network model will be modified by using the decoupled method for easily calculating the distribution of ground fault current on the network. A software package “CDEGS” will be used to analyze the characteristics of each consumer grounding system. The analysis results show that the ground fault on VHV underground loop will produce thousands of voltage of GPR and high touch voltage to damage personnel and equipments. A danger phenomenon has been found that all the consumers fed by the same underground loop will have high GPR due to any one of them occurring ground fault. This danger phenomenon is called “ground fault transfer” which damage all consumers fed by the same underground loop or let them out of service from the loop even they have no ground fault, The mitigation methods for reducing the damage from ground fault transfer are proposed. The information obtained from this study is usefull for improving the performance of underground loop.

並列關鍵字

Underground loops ； Touch Voltage ； Ground Potential Rise ； Ground potential ； Ground Fault Transfer ； Step Voltage

參考文獻

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