【摘要】：換流變壓器作為直流輸電的核心設備之一,其運行的安全可靠性是直流輸電系統(tǒng)正常運行的保證。換流變壓器閥側繞組長期承受交直流復合電壓的作用,絕緣問題也更加復雜。為保證換流變壓器的安全穩(wěn)定運行,需要采取一定措施實現(xiàn)換流變壓器的絕緣缺陷的有效診斷。然而,目前常用的局部放電檢測由于缺乏針對換流變壓器運行工況下的完善診斷依據(jù),絕緣診斷效果并不理想。研究交直流復合電壓下油紙絕緣典型缺陷的發(fā)展過程及放電特性可以為換流變壓器缺陷診斷提供科學的依據(jù)。目前部分典型缺陷下局部放電階段劃分、圖譜特性提取、模式識別等問題已得到了一定的研究。然而,作為極不均勻電場下油紙絕緣缺陷的典型代表,針板缺陷的放電隨機性強,放電特性不穩(wěn)定,其局部放電發(fā)展特性尚未得到充分研究。為了給換流變壓器運行時的油紙絕緣狀態(tài)評估提供更科學的依據(jù),本論文從以下幾個方面開展了工作:(1)通過復合電壓下的油紙絕緣局部放電試驗,研究油紙絕緣針板缺陷模型的放電的發(fā)展過程。基于多種特征量在不同階段的變化規(guī)律,對放電發(fā)展過程進行階段劃分,并對不同發(fā)展階段的放電特性進行分析研究。(2)在不同的復合電壓比例、不同溫度下,進行油紙針板缺陷局部放電試驗并記錄各發(fā)展階段的放電特征。一方面可以研究電壓形式、溫度等外部因素對局部放電發(fā)展過程的影響規(guī)律,另一方面也可以更加全面地模擬換流變壓器實際運行時可能出現(xiàn)的不同溫度、電壓形式等外部條件,為后續(xù)的診斷識別提供樣本數(shù)據(jù)。(3)構造表征局部放電特征的圖譜并提取合適的特征參量,并研究支持向量機、神經(jīng)網(wǎng)絡等方法在復合電壓下油紙針板缺陷局部放電發(fā)展階段識別中的應用,尋找合適的模式識別方法,實現(xiàn)局部放電發(fā)展嚴重程度的診斷識別。
[Abstract]:Converter transformer is one of the core equipment of HVDC transmission. The safety and reliability of converter transformer is the guarantee of the normal operation of HVDC transmission system. Converter transformer valve-side winding bears the function of AC-DC compound voltage for a long time, and the insulation problem is more complicated. In order to ensure the safe and stable operation of converter transformers, some measures should be taken to effectively diagnose the insulation defects of converter transformers. However, the commonly used partial discharge (PD) detection is not satisfactory because of the lack of perfect diagnostic basis for converter transformers. The research on the development process and discharge characteristics of typical defects of oil-paper insulation under AC / DC composite voltage can provide scientific basis for fault diagnosis of converter transformers. At present, some problems have been studied, such as partial discharge phase division, characteristic extraction of pattern, pattern recognition and so on. However, as a typical representative of oil-paper insulation defects in extremely uneven electric field, the discharge randomness of needle board defects is strong, the discharge characteristics are unstable, and the development characteristics of partial discharge have not been fully studied. In order to provide a more scientific basis for the evaluation of oil-paper insulation condition during the operation of converter transformers, the following aspects have been carried out in this paper: (1) the partial discharge test of oil-paper insulation under compound voltage is carried out. The development process of the discharge of the defect model of oil-paper insulating needle board is studied. Based on the variation of various characteristic variables in different stages, the discharge development process is divided into stages, and the discharge characteristics of different development stages are analyzed and studied. (2) at different compound voltage ratios and different temperatures, The partial discharge test of oil-paper needle board defects was carried out and the discharge characteristics of each development stage were recorded. On the one hand, we can study the influence of external factors, such as voltage form and temperature, on the development of partial discharge, on the other hand, we can more comprehensively simulate the different temperatures that may occur in the actual operation of converter transformers. The external conditions, such as voltage form, provide sample data for subsequent diagnosis and identification. (3) constructing the map of partial discharge characteristics and extracting appropriate characteristic parameters, and studying support vector machine. The application of neural network in the development stage of partial discharge (PD) of oil-paper needle board defects under the compound voltage is discussed. A suitable pattern recognition method is found to realize the diagnosis and recognition of the severity of PD development.
【學位授予單位】：中國電力科學研究院
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TM855

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