高科技工廠電力系統開關突波分析

Analysis of Switching Surge at High Tech Industry Power System

邵子興(Zi-Xing Shao)

指導教授 ： 陳士麟 ； 潘晴財

國立清華大學/電機資訊學院/電機工程學系/碩士(2007年)

摘要

早期工廠以架空輸電線饋電，頻傳雷擊事故，為改善此問題，台灣電力公司已將部份的架空輸電線(特別是科學園區內的輸電線)，予以地下化，大幅減低高科技工廠的雷害事故。近期科學園區內有些特高壓工廠發生避雷器事故，造成生產損失，遂擬拆除廠內11.4kV(或22.8kV)避雷器。實際上，在決定避雷器之存廢前，應先探討廠內11.4kV(或22.8kV)系統的過電壓特性。為此，本論文研究科學園區特高壓工廠內的開關突波，而以斷路器切換所引起的突波為研究重點，評估廠內保護11.4kV(或22.8kV)模鑄式變壓器之避雷器是否可予拆除。
本論文採用電磁暫態程式模擬開關突波。首先對於該程式的模擬方法進行探討。由於電磁暫態程式係運用梯形積分法求解微分方程式，而有數值振盪問題，遂有必要選擇適當之模型以避免此問題。據此，本論文針對科學園區內的一家特高壓半導體製造工廠對其廠外69kV地下電纜、69kV六氟化硫變電站、廠內11.4kV架空電纜、69kV及11.4kV變壓器、進相電容器、避雷器、斷路器、理想開關、統計開關與循進式開關等選擇模型，估計模型參數，並模擬半導體工廠斷路器之不同操作模式，運用統計開關模型，分析開關突波的電壓峯值之分佈機率。
模擬結果顯示：在11.4kV模鑄式變壓器的一次側，多數的開關突波會在設備絕緣的容許值的範圍內，但此突波會經由該變壓器的雜散電容耦合至二次側，其峯值卻有可能超過二次側的絕緣容許值，而致有破壞二次側系統設備絕緣的風險。據此建議：若無法承受此項事故風險，廠內保護11.4kV模鑄式變壓器之避雷器仍有設置之必要。

關鍵字

開關突波 ； 電磁暫態程式 ； 數值振盪 ； 循進式開關 ； 統計開關

並列摘要

In the earlier time, Taiwan’s industrial power systems had been fed from Taipower system with overhead transmission lines. Lightning strikes on these lines sometimes caused factory production failures. To reduce lightning outages, in particular of the science park areas, the overhead lines were replaced by Taipower with underground cables. With lightning damages reduced, some high-tech factories recently however encountered arrester failures and are thus planning to dismantle the existing arresters installed to protect the 11.4kV (or 22.8kV) resin-type transformers inside the factory. The decision to dismantle the exiting 11.4kV (or 22.8kV) arresters actually requires in-depth evaluation of the overvoltage characteristics of the high-tech industry power system. For this purpose, the author simulates the transient overvoltage of a 69kV factory power system, focusing on the switching surge, by assuming no lightning can penetrate into the 11.4kV (or 22.8kV) system.
The simulation makes use of the Electromagnetic Transient Program (EMTP) which is based on the trapezoidal rule for solving the transient equations. The solution process is thus efficient but can incur numerical instability. To avoid numerical instability, adequate models should have been selected, and are accordingly selected in this study, for the simulated power system components which include the 69kV underground cable fed to the factory, gas-insulated substation, 11.4kV in-plant overhead cables, transformers, arresters, static capacitors, and the ideal, statistical or systematic switching models for representation of circuit breakers. After model selection, the author then estimates model parameters and simulates the circuit breaker switching sequence of high-tech factories. The simulation applies the statistical switching models. Thus the probability distribution for the voltage peak of switching surge can be evaluated.
The simulation results show that, at the primary side of 11.4kV resin-type transformer, most of the peaks are within the insulation withstand level of transformer, but the surge can be capacitively coupled to transformer’s secondary side with the voltage peak exceeding the insulation withstand level of the secondary system. By accounting for the risk of the secondary system failure, and if the factory owner can not bear this risk, it is suggested the arresters remain as where they are to continue their protecting of the 11.4kV resin-type transformers.

並列關鍵字

Switching Surge ； Electromagnetic Transient Program (EMTP) ； numerical instability ； systematic switching model ； statistical switching model

參考文獻

[1]Y. Li, W. Shi and X. Niu, "A Composite Exponential and Linear MOA Model for Switching Transient Simulation", IEEE Transactions on Power Delivery, Vol. 17, No. 3, pp.730-735, July 2002.

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[4]A. Greenwood, Electrical Transients in Power Systems, 2nd ed., John Wiley, 1991.

[6]A.R. Hileman, Insulation Coordination for Power Systems, Marcel Dekker, 1999.

[7]T. Gonen, Electric Power Transmission System Engineering, John Wiley, 1988.