【作者】 张雪梅；

【导师】 吕玉坤；

【作者基本信息】 华北电力大学 ， 流体机械及工程， 2017， 硕士

【摘要】 大气中污秽颗粒在近输电线路的离子流场中荷电会影响绝缘子周围的电场分布,进而改变颗粒的运动轨迹,影响绝缘子表面的积污状况。因此,有必要研究污秽颗粒荷电对绝缘子积污特性和沿面电场的影响。本文概述了污秽颗粒主要的荷电机理,利用COMSOL对瓷三伞及复合绝缘子在颗粒不同荷电方式下风洞积污特性进行了数值模拟,将积污量的模拟与试验结果进行了对比分析,以验证数值模拟方法的合理性,并探究颗粒相对合理的荷电方式。籍此,对弱风和微风环境110kV直、交流输电线路中,瓷三伞绝缘子的自然积污特性进行了数值模拟,比较了不同风速和粒径下颗粒所受流体曳力、电场力和重力的力比,分析了风速、粒径和污秽浓度等因素对自然积污特性的影响;对清洁和污染环境中瓷三伞绝缘子沿面电场的数值模拟结果进行对比,探究了颗粒在荷电情况下粒径、数量、荷质比、极性等因素对该绝缘子沿面电场的影响。结果表明:1)本文所采用的数值模拟方法是合理的,颗粒“按比例”荷电方式相对而言更具合理性。2)直、交流电压作用下,随风速的增大,绝缘子表面整体积污量先增后减;随污秽浓度增加,积污量均增加且增速减缓,直流时增速大于交流。3)弱风(0.5~2m/s风速)时,直流电压作用下,积污量随粒径增大而增加,交流电压作用下,先增后减;微风(3~5m/s风速)时,直、交流电压作用下,均随粒径增大而增加。4)伞裙几何形状影响绝缘子沿面电势和场强分布,其曲线拐点对应绝缘子表面的特征拐点;各伞裙沿面电势和场强曲线在清洁和污染环境中差异较大。5)伞群场强最大值点发生位置不同:清洁环境发生于铸铁、空气及瓷三者交界;污染环境发生于主要特征拐点处。6)清洁和污染环境场强矢量方向不同:清洁环境从高压端出发终止于低压端;污染环境(粒径足够大)正荷质比时从中间伞裙出发终止于低压端或高压端,负荷质比反之。7)各伞裙沿面场强最大值随粒径、数量、正荷质比增大而增大。8)污染环境伞裙沿面场强最大值可达清洁环境的9~70倍,在一定的条件下易发生局部电弧。更多还原

【Abstract】 Particles will charge in the ion field on the near-transmission line which will affect the distribution of the electric field around the insulator.Changed electric field will change the trajectory of the particles and affect the pollution accumulation of the insulator surface.Therefore,it is necessary to study the influence of particle charge on insulator pollution accumulation characteristics and electric field along the surface.In this paper,the main charge mechanisms of contaminating particles are summarized.COMSOL is used to simulate the pollution accumulation characteristics of porcelain three-umbrella and composite insulators under the different charging modes under wind tunnel test.The simulation results are compared with the experimental results.The reasonableness of the numerical simulation method is analyzed,and the relative reasonable charging way of particles is explored.In particles relatively reasonable charging way,the natural pollution accumulation characteristics of the porcelain three umbrella insulator in 110 kV AC and AC transmission lines in weak winds and breeze were simulated numerically.The relative sizes of drag force,gravity and electric field force are compared.The effects of wind speed,particle diameter,and pollution concentration on the natural pollution accumulation characteristics are analyzed.The electric field along porcelain three-umbrella insulator in clean and polluted environment is numerically simulated.The effects of particle diameter,quantity,charge-to-mass ratio,polarity on the electric field along the surface of charged particles are investigated.The results show that:(1)The numerical simulation method adopted in this paper is reasonable,the particle "proportional" charging way is more reasonable.(2)Under the action of DC and AC voltage,with the increase of wind speed,the pollution accumulation increase first and then decrease.With the increase of pollution concentration,the pollution accumulation increase and the growth rate slow down,the former is faster than the latter.(3)In the weak wind(0.5~2m/s),under the action of DC voltage,the pollution accumulation increases with the increase of particle diameter.Under the action of AC voltage,the pollution accumulation increases first and then decreases with the increase of particle diameter.In the breeze(3~5m/s),under DC and AC voltage,the pollution accumulation increases with the increase of particle diameter.(4)The geometric shape of umbrella skirt can influence potential and electric field distribution of the insulator surface.The potential and electric field strength along the surface curves of each umbrella skirt have different similarities inclean and polluted environments.(5)The maximum value of electric field strength along the surface occurs at the junction of the cast iron,air and porcelain,and the main special inflection points in clean and polluted environments.(6)The direction of the field strength vector is different in the clean and polluted environment,the former from the high voltage end umbrella skirt to the low voltage side;the latter(particle size is large enough)when charge-to-mass ratio is positive from the middle umbrella skirt to the high or low voltage side,when charge-to-mass ratio is negative,the opposite is true.(7)The maximum value of field strength along the surface of each umbrella skirt increases with the increase of particle diameter,number and the absolute value of the charge-to-mass ratio.(8)The field strength maximum value in polluted environment can up to 9 to 70 times in the clean environment.更多还原