交流电场对导线覆冰及其电晕起始特性的影响研究

发布时间：2018-07-29 08:43

【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。
[Abstract]:China has a vast territory, complex terrain and geomorphology and a wide range of microclimate characteristics. About 70% of the land area is in high altitude areas. Therefore, under the development strategy of "west to East power supply, North South mutual supply and national interconnection", transmission lines inevitably need to cross the extreme extreme atmospheric environment areas such as ice covering (snow). The surface of the wire after icing is on the surface. There will be local corona discharge and deposition discharge on the surface of the wire. The problems of the corona loss, electromagnetic pollution and line aging caused by the decline of the halo voltage are paid more and more attention at home and abroad. At present, a lot of experiments have been carried out by scholars in various countries to cover the wire through the artificial climate chamber. However, most of the studies have neglected the actual situation of charged ice on the running wire, and did not deeply study the influence of the ice on the corona voltage and the corona discharge characteristics. Therefore, it is of great academic significance and engineering value to study the influence of different types of ice covering on the starting characteristics of the corona discharge of transmission lines.
In this paper, the corona voltage values of 7 types of wires (different diameters, structures and split numbers) were measured and studied in the artificial climate chamber for the first time in the artificial climate chamber. The experimental results show that the electric field intensity has a very obvious effect on the ice coating on the conductor surface; the ice cover will produce the corona voltage value of the wire. The difference of the corona voltage of the surface of the wire is about 40%~60% before and after the ice coating, and the ice electric field intensity of the glaze and the rime icing wire will rise first and then rise in the course of the increase of 0~20kV/cm, while the rime overlying wire appears up and down in the upward trend, which is due to the roughness of the surface of the ice covered wire. With the increase of ice coating time, the corona voltage of the glaze and the rime overlying wire will continue to decrease, while the corona voltage of the rime overlying wire decreases first and then increases, but the change speed of the corona voltage will gradually slow down and eventually tends to saturation. It will not affect the corona voltage of the rime and the rime coated wire, but the increase of the conductivity will increase the discharge area of the surface of the wet ice, so the corona voltage of the rime overlying wire will decrease.
In this paper, the effect of ice coating roughness coefficient W is first presented to characterize the influence of ice coating on electric field and corona voltage on the surface of wire. In order to study the influence of ice on the electric field of wire, the electric field distribution model of wire surface is established according to different icing forms. The electric field strength of the tip of ice edge is calculated by the finite element method. The results show that: The effect of ice coating on the distortion of electric field of wire is different because of the different roughness of the wire with the same electric field strength. Compared with the clean wire, icing will increase the electric field intensity on the surface of the wire, because the sharp ice edge will cause the distortion of the electric field distribution, and the increase of the icing degree will make the electric field intensity on the surface of the glaze. Because of the dry growth characteristics, the rime will produce a thicker ice thickness on the surface of the wire, thus weakening the influence of the ice branches on the electric field distortion, so the intensity of the electric field on the surface of the rime gradually decreases with the increase of the ice coating time. The effect of the ice coating on the electric field of the wire surface is always the fine wire > coarse wire. The trend of split traverse; using the Matlab to fit the ice coating roughness coefficient W and the corona voltage Uc, the obtained empirical formula can quickly calculate the corona voltage of the wire after the glaze and the rime overlying the ice.
In this paper, the stress situation and corona discharge phenomenon of overcooled water droplets near the wire surface in atmospheric environment were studied in the snow peak mountain natural ice test in Hunan province. The corona discharge and discharge power before and after icing was measured by three stage corona cage and Q-V method. The concentration determines the force in the electric field after the charge of the water droplet. With the increase of the intensity of the electric field, the force of the water droplet will be greater. The corona discharge at the beginning of the ice coating is mainly caused by the deposition discharge. The corona discharge in the process of icing is mainly caused by the discharge of the deposition discharge and the tip of the ice edge, and the corona discharge after the ice cessation is almost all the source. The discharge of the ice surface at the tip of ice, the discharge of the deposition and the corona discharge of the ice surface are all random and approximate to the normal distribution, and the corona discharge of the negative half cycle will peak with the increase of the icing time, and then the corona discharge will continue to increase until it is saturated, and then slightly decreases; positive, negative half week. The total discharge in the period is almost the same, and the discharge amount in only a few period is not consistent; the discharge power of the 5~10kV/cm electric field is smaller than the rime, while the 15~20kV/cm situation is just the opposite; the electric discharge of the rime overlying wire is almost not affected by the electrical conductivity, and the discharge quantity and discharge of the wire after the glaze icing is put on. The electrical power increases with the increase of electrical conductivity, but the discharge amplitude of rime icing at 20kV/cm is less than 10kV/cm when the amplitude of discharge is affected by electrical conductivity.
【学位授予单位】：重庆大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TM752

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