以長距離電纜併聯之大型電廠接地故障對電纜及接地系統之影響研究

Affections of Ground Fault on the Cable and Grounding System in the Large Plants with Long Cpble Interconnections

曾盈昌(Ying-Chang Tzeng)

指導教授 ： 何金滿 ； 周至如

中原大學/工學院/電機工程研究所/碩士(2006年)

https://doi.org/10.6840/cycu200600258

摘要

摘要
大型電廠內的機組若以長距離電纜併聯至開關廠則開關廠發生接地故障時，大電流及高電壓將出現在接地系統與電纜遮蔽層導體，可能造成對人員與設備及電纜本身的傷害，本論文將以典型的案例探討這些問題，首先應用電磁暫態分析程式(EMTP/ATP)建構電路模型，並進行接地故障分析，包括穩態及暫態之分析。模型的建構將考慮開關廠及開關地網，電纜相導體及遮蔽層導體，機組地網及機組主變壓器。其中電纜遮蔽層導體交錯換位連接及經電纜被覆保護裝置器(CCPU)之避雷器接地，將考慮在模型當中，而機組主變壓器及起動變壓器中性點之接地方式，包括直接接地及經避雷器接地都將分別加以分析。經由ATP分析的結果可獲得電纜遮蔽層之電流及電壓分佈狀況以及開關場與機組地網之注入電流狀況。最後再根據這些結果可進一步評估對電纜的影響及對接地系統的影響，前者將檢討對電纜遮蔽層導體之連接處及CCPU之避雷器等可能遭受的危害，至於對接地系統影響的評估，則先應用接地系統分析軟體(CDEGS)來分析地網電磁暫態特性包括地電位昇、接觸電壓、步間電壓及地表電磁場之分析，並藉此評估對於人員與設備的影響，整體而言經分析結果顯示，人員及設備於開關場或觸及電纜遮蔽層導體其安全將受到威脅，而電纜遮蔽層上的電流及電壓可達數kA及數kV，在連接處若處理不當很容易引發電纜損壞釀成更大的傷害。

關鍵字

電纜遮蔽層導體 ； 避雷器 ； 電纜被覆保護裝置器 ； 步間電壓 ； 接觸電壓 ； 地電位昇 ； 地表電位磁場

並列摘要

Abstract
In the large plant with long cables interconnection between generator units and switchyard , large current and high voltage will appear on the cable shielding conductors and grounding system during ground fault on switchyard. Form which the cable and equipment may be damaged even hurt personnel. In this thesis , typical plant with the above problems is studied , The circuit model based on electromagnetic transient program/alternative transient program (EMTPATP) is constructed and analyzed for ground fault on the switchyard at transient state and steady state . The ground grids of switchyard and generator units , the phase conductor and shielding conductors of cable and the main transformer of generation unit are all considered in the modal . In which , the cable shielding conductor with cross-transposition-connection and grounded by arrester in the cable-cover-protection unit (CCPU) are detailly considered in the model . The grounded types of neutral points of mantransformers of generator unit and starting transformer include solid-grounded and arrester-grounded type which are considered is the analysis of ground fault . The transient state and steady state currents and voltages distributed on the cable shielding conductors and the grounding points of cable shielding conductors and transformer neutral point on the ground grids can be obtained from the simulation by ATP . Finally , the affections of ground fault on the cable and grounding system are evaluated lased on the simulation results. In which , the damages on the connections and CCPU arresters of cable shielding conductor are surveied and the electromagnetic characteristics of ground grids are further analyzed by a software package, namely, “current distribution electromagnetic grounding and soil structure analysis”(CDEGS). From which ,we can obtain the electromagnetic the distribution of ground potential rises (GPR) , touch voltage ,step voltage and electromagnetic field on the ground surface of ground grids of switchyard and generate unit . Based on the electromagnetic characteristics , their affections on personnel and equipment are assessed . In the whole ,the study results have shown that the personnel and equipments will be danger at switchyard and touch to cable may shielding conductor during ground fault , and the cable may be damaged by large current with several kA and high voltage kV on the shielding
conductors if their connection parts are not treated well.

並列關鍵字

arrester ； shielding conductor ； cable-cover-protection unit ； ground potential rises ； touch voltage ； step voltage ； electromagnetic field

參考文獻

[25] 胡開泰，多地網大型接地系統接地故障之電磁特性研究，中原大學電機研究所碩士論文，民國九十年六月。

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