發(fā)布時間：2018-05-25 06:04

  本文選題：溝槽電纜 + 局部放電��； 參考：《沈陽工業(yè)大學》2017年碩士論文

【摘要】：隨著現(xiàn)代工業(yè)的發(fā)展和城市化水平的提高,電纜作為傳輸電能的重要工具,越來越得到人們的重視,其運行的可靠性直接影響電力系統(tǒng)的正常運行。然而電纜在運行中難免會遇到一些故障,主要是由于在電纜絕緣材料中容易產(chǎn)生局部放電現(xiàn)象,電纜絕緣材料在生產(chǎn)時由于加工技術(shù)的限制或者原材料有問題,導致加工完后絕緣中存在雜質(zhì)或氣隙,氣隙和雜質(zhì)尖端處是最容易發(fā)生局部放電現(xiàn)象的區(qū)域。電纜局部放電的大小與電纜絕緣狀況的好壞息息相關(guān),局部放電量的增加表示電纜的絕緣強度在減弱,這會危害電纜的安全運行,因此提前并準確檢測局部放電的強弱是避免電纜故障最有效的方法。目前主要是定點或在離線狀態(tài)下對電纜局部放電進行檢測,針對傳統(tǒng)方法檢測電纜局部放電的局限性,本文對電纜局部放電超聲波檢測法進行深入研究。本文基于電纜絕緣層三電容模型和氣隙放電力學模型解釋局部放電現(xiàn)象以及分析局部放電產(chǎn)生超聲波的機理,研究局部放電的分類和產(chǎn)生原因,同時研究局部放電超聲波信號的波形特征,為電纜局部放電超聲波檢測法給予理論支持。針對電纜局部放電超聲波信號,研究局部放電超聲波信號的傳播特性,分析局部放電超聲波信號的頻率和幅值信息,以及環(huán)境中可能存在的各種干擾信號,以此作為基礎(chǔ),選取適合電纜局部放電現(xiàn)場檢測的超聲波接收探頭,設(shè)計信號放大、濾波等處理電路,通過計算和分析選取合適的電路參數(shù),利用STM32單片機處理和存儲模擬轉(zhuǎn)換后的信號,并對電路進行了仿真和測試。利用MATLAB的GUI功能編寫用戶界面對數(shù)據(jù)進行處理,能夠顯示超聲波信號波形,提取信號的包絡(luò),顯示信號最大幅值及放電起始點。通過系統(tǒng)的實驗研究,分析超聲波接收探頭中心頻率、放電強弱以及距放電源距離對局部放電超聲波信號的影響。研究結(jié)果表明局部放電能夠產(chǎn)生類似于AM調(diào)制的超聲波信號,且信號幅值與放電量成正比,與探頭和放電源之間的距離成反比,在局部放電信號頻率范圍內(nèi),低頻段局部放電信號的幅值較大,本文中探頭的最優(yōu)中心頻率為27kHz,采用中心頻率為27kHz的接收探頭時,局部放電檢測裝置的有效檢測距離為80cm,應(yīng)用MATLAB提取局部放電信號的包絡(luò),能夠直觀地分析信號幅值及放電起始點,為判斷局部放電有無、放電量大小及位置提供有效的依據(jù)。
[Abstract]:With the development of modern industry and the improvement of urbanization level, more and more attention has been paid to cable as an important tool to transmit electric energy. The reliability of cable operation directly affects the normal operation of power system. However, some faults will inevitably be encountered in the operation of the cable, mainly because partial discharge is easy to occur in the cable insulation material, and the cable insulation material is produced because of the limitation of processing technology or the problem of raw materials. After processing, there are impurities or air gaps in the insulation, and the air gap and impurity tip are the areas where partial discharge is most likely to occur. The magnitude of partial discharge of cable is closely related to the insulation condition of cable. The increase of partial discharge indicates that the insulation strength of cable is weakening, which will endanger the safe operation of cable. Therefore, early and accurate detection of partial discharge is the most effective method to avoid cable faults. At present, partial discharge of cable is mainly detected at fixed point or off-line state. Aiming at the limitation of traditional method of detecting partial discharge of cable, the ultrasonic detection method of partial discharge of cable is studied deeply in this paper. Based on the three capacitance model of insulation layer and the mechanical model of air gap discharge, this paper explains the phenomenon of partial discharge and analyzes the mechanism of partial discharge producing ultrasonic wave, and studies the classification and cause of partial discharge. At the same time, the waveform characteristics of partial discharge ultrasonic signal are studied to provide theoretical support for cable partial discharge ultrasonic detection method. According to the ultrasonic signal of partial discharge of cable, the propagation characteristic of ultrasonic signal of partial discharge is studied, and the frequency and amplitude information of ultrasonic signal of partial discharge are analyzed, as well as various kinds of interference signals that may exist in the environment. The ultrasonic receiver which is suitable for the field detection of partial discharge of cable is selected, the signal amplification and filter are designed, the suitable circuit parameters are selected by calculation and analysis, and the signal after analog conversion is processed and stored by STM32 single chip computer. The circuit is simulated and tested. Using the GUI function of MATLAB to write the user interface to process the data, the ultrasonic signal waveform can be displayed, the envelope of the signal can be extracted, the maximum value of the signal and the starting point of discharge can be displayed. The influence of the center frequency of ultrasonic receiver probe, discharge intensity and distance from the discharge source on the ultrasonic signal of partial discharge is analyzed. The results show that partial discharge can produce an ultrasonic signal similar to AM modulation, and the amplitude of the signal is proportional to the discharge quantity, and inversely proportional to the distance between the probe and the discharge source, and in the frequency range of the partial discharge signal. The amplitude of PD signal in low frequency band is large. The optimum center frequency of probe is 27kHz. When the receiver with 27kHz central frequency is adopted, the effective detection distance of PD detector is 80 cm. The envelope of PD signal is extracted by MATLAB. The signal amplitude and the starting point of the discharge can be analyzed intuitively, which provides an effective basis for judging whether the partial discharge exists, the magnitude and the position of the discharge.
【學位授予單位】：沈陽工業(yè)大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TM855

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本文編號：1932385