【作者】 陈吉；

【导师】 蒋兴良；

【作者基本信息】 重庆大学 ， 电气工程， 2014， 博士

【摘要】 我国幅员辽阔、地形地貌复杂且微气候特征繁多，约70%的国土面积处于高海拔地区，因此在“西电东送、南北互供、全国联网”的电力发展战略下，输电线路不可避免地需要穿越覆冰(雪)等极端恶劣的大气环境地区。覆冰后的导线表面由于粗糙程度发生变化，因此导线表面会出现局部电晕放电和沉积放电等现象，由起晕电压下降引起的输电线路电晕损耗、电磁污染、线路老化等问题愈加受到国内外重视。目前各国学者通过人工气候室对导线覆冰进行了大量试验研究，但大多数研究均忽略了运行导线发生带电覆冰的实际情况，也未深入研究覆冰对导线起晕电压以及电晕放电特性的影响规律，因此本文开展不同类型覆冰对输电线路电晕放电起始特性影响的研究具有重要的学术意义和工程价值。本文首次结合紫外成像技术和曲线拟合法在人工气候室内针对7种类型(不同直径、结构和分裂数)导线覆冰前后的起晕电压值进行测量研究。试验结果表明：电场强度对导线表面的覆冰形态影响极为明显；覆冰会对导线起晕电压值产生较大影响，覆冰前后导线表面的起晕电压值相差约为40%~60%左右；覆冰电场强度从0~20kV/cm增加过程中，雨凇和混合凇覆冰导线的起晕电压会先下降后上升，而雾凇覆冰导线则出现上下波动的趋势，这是由于覆冰导线表面的粗糙程度不同引起的；覆冰时间的增加会使雨凇和混合凇覆冰导线起晕电压持续下降，而雾凇覆冰导线起晕电压则先下降后升高，但起晕电压的变化速度均会逐渐变慢并最终趋于饱和。覆冰水电导率对交流电场下的导线覆冰形态几乎没有影响，也不会对雾凇和混合凇覆冰导线的起晕电压产生影响，但电导率的增加会使湿冰表面放电区域扩大，因此雨凇覆冰导线起晕电压会下降。本文首次提出了覆冰粗糙系数W以表征覆冰对导线表面电场及起晕电压的影响程度。为研究覆冰对导线电场的影响规律，本文根据不同覆冰形态建立了导线表面的电场分布模型，利用有限元法计算了冰棱尖端的电场强度。结果表明：不同电场强度覆冰后的导线由于粗糙程度不同，因此覆冰对导线电场的畸变影响也不同；和清洁导线相比，覆冰会使导线表面电场强度增大，这是由于尖锐的冰棱会使电场分布发生畸变引起的；覆冰程度的增加会使雨凇表面电场强度继续增大；雾凇由于干增长特性会在导线表面生成较粗的冰厚，从而弱化冰树枝对电场畸变的影响，故雾凇表面电场强度程度随覆冰时间的增加而逐渐减小；相同覆冰时间内，覆冰对导线表面电场的畸变作用，始终是细导线＞粗导线＞分裂导线的趋势；利用Matlab对覆冰粗糙系数W和起晕电压Uc进行拟合，所得到的经验公式可以快速计算雨凇和雾凇覆冰后的导线起晕电压。本文首次在湖南省雪峰山自然覆冰试验现场研究了大气环境中过冷却水滴靠近导线表面时的受力情况和电晕放电现象，利用三段式电晕笼和Q-V法对导线覆冰前后的电晕放电量和放电功率等信号进行了测量研究。结果表明：空间离子浓度决定了水滴荷电后在电场中的受力情况，随着电场强度的增加水滴受力也会更大；覆冰之初的电晕放电主要由沉积放电引起，覆冰过程中的电晕放电主要由沉积放电和冰棱尖端放电引起，而覆冰停止后的电晕放电几乎全部来源于冰棱尖端的放电作用；覆冰过程的沉积放电和冰面电晕放电量均具有随机性且近似服从正态分布；正、负半周期的电晕放电量会随覆冰时间的增加而出现峰值，之后电晕放电量会继续增加直至出现饱和，最后略微减少；正、负半周期的总放电量几乎都相同，仅少部分周期的放电量不一致；5~10kV/cm电场强度下雨凇的放电量、放电功率比雾凇下小，而15~20kV/cm情况则正好相反；不同电导率对雾凇覆冰导线的电晕放电量几乎没有影响，而雨凇覆冰后导线的放电量与放电功率均随电导率的增加而增加，但雨凇覆冰在20kV/cm下的放电量幅值受电导率的影响小于10kV/cm时的情况。更多还原

【Abstract】 China has a large land area and most places about70%are at high altitudes whilethe micro climate characteristics are various, due to the development strategy of “powertransmission from west to East, mutual supply between South and North, nationwideinterconnection”, the transmission lines have to go across some extremely complexenvironments such as icy, snowy or rainy climates and so on during the transmissionprocess. And roughness brought by external surroundings will directly affect the safetyoperation of the power grid. Super-cooled water droplets may cause the micro-dischargeunder the affection of winds when they are close to the transmission line surface, andthe ice on conductor surface will change the original shapes or even causes the partialcorona effect, which may lead to the conductor’s corona onset voltage decline andcorona loss. Electromagnetic pollution, circuit aging problems caused by thisphenomenon should be paid more attention. At present, the domestic and foreignscholars have carried out some researches on transmission line icing, but most of themignored the practical significance of energized icing, so there are some differencesbetween the theoretical conclusions and engineering practices. And in addition, theydidn’t study the influence law of ice on corona onset voltage and corona dischargethoroughly. Therefore in this paper, researches were carried out on the impact ofdifferent ice coating types on the corona onset characteristics of transmission line whichhas important academic significance and engineering value.In this paper, the artificial climate chamber was used to simulate three kinds ofcommon icing types, namely glaze, rime and mixed-phase icing, while seven different(in diameters, types and splits) kinds of conductors were iced in this chamber underdistinct field strength. Optical radiation mechanism based on the cathode surface,combined with the UV imaging technology and the photon number fitting were firsttime used to analyze the corona onset voltage of conductors before and after the icecoating. Results show that: the shapes of conductors’ surfaces are very different whenthey were iced in different fields. Corona onset voltage values of bare wire are largerthan those of iced conductors, even minimal icing will decline the corona onset voltagevalues to about40%~60%of bare wires’ values. As the field strength increases from0to20kV/cm, the inception voltage of glaze and hard rime icing surface firstlydecreased and then increased, while the soft rime surface showed a fluctuation trend which dropped, rose, dropped again and rose again, the difference was due to thedistinct ice shapes which formed in diverse field strengths. Corona onset voltage of theglaze and mixed-phase icing surface declined continuously along with the increase ofthe ice extent, while the rime surface first decreased and then increased, the change rateof them slowed down gradually with the ice amount saturated. The conductivity withdifferent concentrations had little effect on the ice morphology, and it would not affectthe corona inception voltage of rime and mixed-phase icing, higher conductivityincreased the discharge area of glaze surface and led to corona inception voltage dropeventually.This paper presents for the first time the ice roughness coefficient W tocharacterize how the icing affects the field strength and corona onset voltage. To studythe influence of ice coating on the wire surface field, this paper established the fielddistribution model according to the different icing shapes, maximum field strength oficed surface was calculated by using the finite element method, the concept of icingroughness coefficient W was put forward to characterize the how the icing affect thefield distribution and corona onset voltage. Results show that: different AC field leads todistinct ice morphology and roughness, so the electric field distortion on the wiresurface by icicle is different. Compared to the bare wire, ice will raise the electric fieldstrength on conductor surface greatly, this is because the ice surface is so rough that theicicle tips will distort the field. Increase of ice extent will distort the electric field ofglaze surface more seriously, while the increase speeds of partial field strength slowsdown. Rime’s dry growth characteristics will produce greater ice thickness, thus mayweaken the distortion effect of ice-tree, so the maximum field strength of rime surfacewill be reduced with the increasing icing time. During the same icing time, distortioneffect on electric field always shows a trend namely a thin wire> coarse wire> bundleconductor. The ice roughness coefficient W and corona onset voltage Ucare fitted byMatlab, the empirical formula obtained can quickly calculate the glaze and rime icingconductor’s corona onset voltage.To study the corona discharge caused by super-cooled water droplets close to thewire surface, the test was established for the first time in Hunan province Xuefengmountain, combined with the corona cage and Q-V method to analyze the coronadischarge quantity and discharge power during the energized icing, results show that:the force tendency of water droplets in the field after charged was decided by the ionconcentration, the force extent will increase as the background field strength rises. At the beginning of icing, corona discharge on the wire surface is the mainly caused by themicro discharge, then during the icing process is mainly caused by the water dropletsand rough surface, and the corona discharge was mostly caused by the icicle tips afterthe icing stops. Micro discharge and corona discharge on the conductor surface are allrandom which approximate the normal distribution. The positive and negative coronadischarge will reach the peak level with the increase in icing time, and then the coronadischarge will be saturated or even slightly reduced later. The total discharge quantitiesof positive and negative are almost the same, only a small part of the discharge cycle isnot consistent. Discharge capacity and power of glaze are smaller than the rime under5~10kV/cm, but in15~20kV/cm the situation is opposite. Different conductivity hasno effect on the rime discharge capacity, while the discharge quantity and dischargepower of glaze increased as the conductivity rose, the glaze discharge amplitude in20kV/cm influenced less than10kV/cm by conductivity.更多还原