【摘要】：自由金屬微粒是制約直流氣體絕緣線路(DC gas insulated line,GIL)絕緣耐受能力的重要因素。在電場力作用下,直流GIL中的自由金屬微粒可運動至高壓電極或絕緣子附近,引發(fā)局部放電或氣隙擊穿,對直流GIL的絕緣性能造成巨大的威脅。本文針對自由金屬微粒運動引發(fā)的局部放電問題,結(jié)合其運動行為研究影響放電特性的因素以及危險程度判別。首先,采用同軸圓柱腔體和線形金屬微粒為試驗?zāi)Ｐ?搭建直流高壓局部放電試驗平臺,針對電壓極性、幅值、微粒長度、半徑、SF6氣壓、微粒個數(shù)等影響微粒放電特性的因素開展直流高壓試驗。利用脈沖電流法及高速相機同時觀察記錄其局部放電信號與運動行為,對微粒的運動特性與放電特性進行分析,探究各因素對線性金屬微粒的運動特性及放電特性的影響。其次,對影響微粒放電物理機制的因素進行深入分析,探討不同因素的作用機理,并定量分析不同因素的影響。而后,利用COMSOL軟件對不同長度、半徑、位置的線性金屬微粒對電場分布的影響進行仿真分析。最后,綜合考慮試驗、仿真結(jié)果以及放電機理,探究微粒的危險程度。結(jié)果表明:微粒的局部放電與運動活性隨著直流電壓幅值的提高而更加劇烈,由于直流極性效應(yīng),微粒在負電壓作用下發(fā)生“飛螢”現(xiàn)象,在負電壓下的局部放電較正電壓下的更為劇烈,對絕緣的威脅更嚴重。隨著微粒長度的增加,微粒的局部放電更加劇烈,而運動角度范圍隨之減小。隨著微粒半徑的提高,微粒的起跳電壓升高,當(dāng)半徑大于一定值時,微粒保持靜止,危險程度隨之降低。隨著氣壓增大,氣體的局部放電隨之減弱,微粒的運動范圍減小,但絕緣效果有趨于飽和的趨勢。多個微粒同時運動時,微粒的平均局部放電量略有提高,但放電頻次明顯增加,且在空氣環(huán)境中,出現(xiàn)兩個微粒在同一徑向運動并引發(fā)串聯(lián)氣隙擊穿的現(xiàn)象,危險程度增加。微粒對電場分布的畸變效應(yīng)與長度呈正相關(guān),與半徑呈負相關(guān),最大電場強度均出現(xiàn)在不與電極接觸的一端,且與高壓電極接觸時的電場畸變效應(yīng)最嚴重。因此,微粒的危險程度與其個數(shù)、長度呈正相關(guān);當(dāng)微粒的半徑大于一定值時,微粒靜止不構(gòu)成危險,可進一步根據(jù)微粒的局部放電信號判斷其危險程度及微粒長度。本文研究有利于深化微粒的放電物理機制的研究,為進一步實現(xiàn)危險程度評估定量化分析提供了一定的理論指導(dǎo)。
[Abstract]:Free metal particles are important factors that restrict the insulation tolerance of DC gas insulated lines (DC gas insulated line,GIL). Under the action of electric field force, free metal particles in DC GIL can move to the vicinity of high voltage electrode or insulator, causing partial discharge or air gap breakdown, which poses a great threat to the insulation performance of DC GIL. In this paper, according to the problem of partial discharge caused by the movement of free metal particles, the factors affecting discharge characteristics and the discrimination of risk degree are studied in combination with their motion behavior. Firstly, using coaxial cylindrical cavity and linear metal particles as experimental models, the DC high voltage partial discharge test platform is built, aiming at voltage polarity, amplitude, particle length, radius, SF6 pressure. The DC high voltage test was carried out for the factors affecting the discharge characteristics of the particles, such as the number of particles. The pulse current method and high-speed camera were used to observe and record the partial discharge signal and the motion behavior of the particles. The motion characteristics and discharge characteristics of the particles were analyzed and the effects of various factors on the motion characteristics and discharge characteristics of the linear metal particles were investigated. Secondly, the factors influencing the physical mechanism of particle discharge are analyzed deeply, and the action mechanism of different factors is discussed, and the influence of different factors is analyzed quantitatively. Then, the influence of linear metal particles with different length, radius and position on electric field distribution is simulated and analyzed by COMSOL software. Finally, considering the experiment, simulation results and discharge mechanism, the dangerous degree of particles is discussed. The results show that the partial discharge and motion activity of the particles are more intense with the increase of DC voltage amplitude. Due to the DC polarity effect, the particles appear "firefly" phenomenon under the negative voltage action. Partial discharge under negative voltage is more severe than that under positive voltage, and the threat to insulation is more serious. With the increase of particle length, the partial discharge of particles becomes more intense and the range of motion angle decreases. With the increase of the particle radius, the take-off voltage of the particle increases. When the radius is larger than a certain value, the particle remains stationary and the dangerous degree decreases. With the increase of the gas pressure, the partial discharge of the gas decreases and the moving range of the particles decreases, but the insulation effect tends to saturate. When several particles are moving at the same time, the average local discharge of the particles increases slightly, but the frequency of discharge increases obviously. In the air environment, two particles move in the same radial direction and cause the breakdown of the air gap in series, and the danger degree is increased. The distortion effect of particles on the distribution of electric field is positively correlated with the length and negatively with the radius. The maximum electric field intensity appears at the end without contact with the electrode, and the electric field distortion effect is the most serious in contact with the high voltage electrode. Therefore, the danger degree of particles is positively correlated with the number and length of particles, and when the radius of particles is larger than a certain value, the particles are not dangerous at rest, so the danger degree and the length of particles can be further judged according to the partial discharge signal of particles. The research in this paper is helpful to deepen the research on the physical mechanism of particle discharge and provide some theoretical guidance for the further quantitative analysis of risk assessment.
【學(xué)位授予單位】：華北電力大學(xué)(北京)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TM75

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