【摘要】：隨著高壓直流輸電的迅速發(fā)展,換流變壓器作為聯(lián)接交流電網(wǎng)和直流線路的重要設(shè)備,絕緣問題是保證其可靠運(yùn)行的關(guān)鍵。換流變壓器與電力變壓器有很大的不同,其承受的電壓類型有穩(wěn)態(tài)直流電壓、工頻交流電壓、極性反轉(zhuǎn)電壓、雷電沖擊電壓和操作沖擊電壓。因此研究復(fù)合電場(chǎng)作用下?lián)Q流變壓器閥側(cè)繞組的電場(chǎng)分布特性及影響因素對(duì)換流變壓器的絕緣設(shè)計(jì)具有重大意義。本文根據(jù)實(shí)際±500kV換流變壓器的絕緣結(jié)構(gòu),建立換流變壓器結(jié)構(gòu)模型,確定電場(chǎng)計(jì)算的數(shù)學(xué)模型,并給出相應(yīng)的邊界條件。首先利用有限元分析軟件計(jì)算了換流變壓器在穩(wěn)態(tài)直流電壓作用下電場(chǎng),給出電場(chǎng)分布和最大電場(chǎng)強(qiáng)度值及出現(xiàn)的位置,分析得出影響電場(chǎng)分布的因素。其次計(jì)算了工頻交流電壓作用下電場(chǎng)分布,并與直流穩(wěn)態(tài)電壓作用下相比較,分析得出不同于直流電場(chǎng)的影響因素。計(jì)算交流電壓疊加直流電壓作用下電場(chǎng)分布時(shí),采用交直流線性疊加的方法,得出電場(chǎng)分布特性及其影響因素。換流變壓器承受的極性反轉(zhuǎn)電壓是與普通電力變壓器最不同的特性。由于極性反轉(zhuǎn)電壓的特征,使絕緣介質(zhì)出現(xiàn)非線性,本文研究了溫度對(duì)絕緣介質(zhì)非線性的影響。通過有限元數(shù)值計(jì)算方法與軟件相結(jié)合對(duì)換流變壓器的二維漏磁場(chǎng)模型進(jìn)行了計(jì)算,將計(jì)算所得到的損耗值利用熱源加載的方式施加在換流變壓器的鐵芯和繞組上,仿真得到換流變壓器二維溫度場(chǎng)分布情況,為分析考慮溫度梯度影響時(shí)換流變壓器在極性反轉(zhuǎn)電壓下的電場(chǎng)分布提供了依據(jù)。對(duì)換流變壓器閥側(cè)繞組在極性反轉(zhuǎn)電壓下進(jìn)行仿真計(jì)算,得出內(nèi)部電場(chǎng)的變化規(guī)律和電場(chǎng)分布的影響因素以及最大電場(chǎng)強(qiáng)度。由于溫度對(duì)電阻率的非線性影響,對(duì)比分析未考慮溫度影響和考慮溫度影響時(shí)極性反轉(zhuǎn)電場(chǎng)的分布,以及不同介質(zhì)電場(chǎng)強(qiáng)度的變化趨勢(shì)。本文得出的結(jié)論和研究方法,對(duì)換流變壓器的絕緣分析及結(jié)構(gòu)設(shè)計(jì)提供了依據(jù)和參考。
[Abstract]:With the rapid development of HVDC transmission, converter transformer as an important equipment to connect AC network and DC line, insulation is the key to ensure its reliable operation. Converter transformers are very different from power transformers. Their voltage types include steady-state DC voltage, power frequency AC voltage, polarity reversal voltage, lightning impulse voltage and operating impulse voltage. Therefore, it is of great significance to study the electric field distribution characteristics of converter transformer valve side windings and the influencing factors for insulation design of converter transformer under the action of complex electric field. According to the insulation structure of the actual 鹵500kV converter transformer, the structural model of the converter transformer is established, the mathematical model of electric field calculation is determined, and the corresponding boundary conditions are given. Firstly, the electric field of converter transformer under steady DC voltage is calculated by using finite element analysis software. The distribution of electric field, the value of maximum electric field intensity and the position of occurrence are given, and the factors influencing the distribution of electric field are analyzed. Secondly, the distribution of electric field under the action of power frequency AC voltage is calculated, and compared with that under DC steady voltage, the factors which are different from DC electric field are analyzed. When calculating the distribution of electric field under the action of AC voltage and DC voltage, the characteristics of electric field distribution and its influencing factors are obtained by the method of AC / DC linear superposition. The polarity reversal voltage of converter transformer is the most different from ordinary power transformer. The influence of temperature on the nonlinearity of insulating dielectric is studied in this paper because of the characteristic of polarity reversal voltage. The 2-D flux leakage model of converter transformer is calculated by means of finite element method and software. The calculated loss value is applied to the core and winding of converter transformer by the way of heat source loading. The two-dimensional temperature field distribution of converter transformer is obtained by simulation, which provides a basis for analyzing the electric field distribution of converter transformer under polarity reversal voltage considering the influence of temperature gradient. Under the polarity reversal voltage, the variation law of internal electric field, the influencing factors of electric field distribution and the maximum electric field intensity are obtained by simulating the valve winding of converter transformer under the polarity reversal voltage. Because of the nonlinear effect of temperature on resistivity, the distribution of polarity reversal electric field and the change trend of electric field intensity in different medium are analyzed by contrast. The conclusion and research method provided basis and reference for insulation analysis and structure design of converter transformer.
【學(xué)位授予單位】：沈陽工業(yè)大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TM41

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