本文選題：換流變壓器　切入點：極性反轉(zhuǎn)　出處：《華北電力大學(xué)》2014年碩士論文

【摘要】：目前世界上許多電力大國都采用高壓直流輸電技術(shù)來解決高電壓、遠距離、大容量送電和電網(wǎng)互聯(lián)問題。直流輸電系統(tǒng)中一次設(shè)備故障是引起直流系統(tǒng)強迫停運的首要因素,其中,以換流變壓器故障引起的直流系統(tǒng)被迫停運次數(shù)最多。 在運行中,作用在換流變壓器上的除了有高幅值的直流和交流工作電壓,以及雷電過電壓等各種過電壓外,還要承受啟動、停運和極性反轉(zhuǎn)等動態(tài)直流電壓。由于電導(dǎo)率會隨著溫度、電場強度等的變化而在很大范圍內(nèi)發(fā)生改變,而靜態(tài)和瞬態(tài)直流電場的分布情況又與電導(dǎo)率密切相關(guān),所以這種不確定性為直流絕緣的設(shè)計帶來了很大的困難。故深入研究換流變壓器極性反轉(zhuǎn)瞬態(tài)電場分布特征對換流變壓器的設(shè)計、制造和維護具有重要意義。 本文首先在電準(zhǔn)靜態(tài)場條件下,利用罰函數(shù)法整合邊界條件,建立了以節(jié)點電位為變量的有限元狀態(tài)方程,同時對比分析了求解有限元狀態(tài)方程的幾種數(shù)值方法。 針對一臺實際換流變壓器,通過將有限元數(shù)值計算方法與Ansoft商用軟件結(jié)合使用對其鐵芯及繞組損耗的情況進行了計算,隨后又利用Gambit軟件對該變壓器(包括周圍油紙絕緣結(jié)構(gòu))建立了可用于數(shù)值計算的模型,對模型進行了參數(shù)設(shè)置,并將計算所得的損耗數(shù)據(jù)作為面積熱源對應(yīng)施加到換流變壓器鐵芯和繞組上,用Fluent軟件仿真計算得到了該換流變壓器的二維分布云圖。計算結(jié)果為后續(xù)考慮溫度梯度對換流變壓器極性反轉(zhuǎn)過程的影響提供了數(shù)據(jù)支撐。 最后討論并分析了一臺實際的換流變壓器及其出線套管在考慮電場強度-電導(dǎo)率,溫度-電導(dǎo)率等非線性條件下的極性反轉(zhuǎn)瞬態(tài)電場分布,并與線性情況的計算結(jié)果進行了對比分析,考察了非線性對換流變壓器及其出線套管極性反轉(zhuǎn)電場分布的影響,為進行換流變壓器及其出線套管的絕緣結(jié)構(gòu)設(shè)計提供依據(jù)。
[Abstract]:At present, many power countries in the world adopt HVDC technology to solve the problems of high voltage, long distance, large capacity power transmission and power network interconnection. The primary equipment failure in HVDC transmission system is the primary factor that causes the forced outage of DC system. The DC system caused by converter transformer fault is forced out of operation. In operation, in addition to DC and AC operating voltages with high amplitude and various overvoltages such as lightning overvoltages, those acting on converter transformers are also subject to start-up. Dynamic DC voltage such as outage and polarity reversal. The electrical conductivity changes in a large range with the change of temperature and electric field intensity, and the distribution of static and transient DC field is closely related to the conductivity. Therefore, it is very difficult to design DC insulation because of this uncertainty, so it is very important for the design, manufacture and maintenance of converter transformers to deeply study the characteristics of transient electric field distribution of polarity reversal in converter transformers. In this paper, a finite element equation of state with node potential as a variable is established under the condition of electric quasi static field and the penalty function method is used to integrate the boundary condition. At the same time, several numerical methods for solving the finite element equation of state are compared and analyzed. For a practical converter transformer, the loss of its core and winding is calculated by combining the finite element numerical method with Ansoft commercial software. Then a numerical model of the transformer (including the surrounding oil-paper insulation structure) is established by using Gambit software, and the parameters of the model are set up. The calculated loss data is applied to the core and winding of converter transformer as the corresponding area heat source. The two-dimensional distribution cloud diagram of the converter transformer is obtained by using Fluent software, and the results provide data support for the subsequent consideration of the effect of temperature gradient on the polarity reversal process of converter transformer. Finally, the polarity reversal transient electric field distribution of an actual converter transformer and its outlet bushing under nonlinear conditions such as electric field intensity-conductivity, temperature-conductivity and so on is discussed and analyzed. The results are compared with the linear results, and the influence of nonlinearity on the polarity reversal electric field distribution of converter transformer and its outlet bushing is investigated, which provides the basis for the insulation structure design of converter transformer and its outlet bushing.
【學(xué)位授予單位】：華北電力大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2014
【分類號】：TM721.1

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本文編號：1682305