【作者】 张程；

【导师】 杜伯学； 王浩鸣；

【作者基本信息】 天津大学 ， 电气工程， 2018， 硕士

【摘要】 高压直流电力设备是远距离大容量电能输送和新能源消纳系统的重要组成部分。但是电场畸变现象广泛存在于高压直流输电关键设备之中,不仅会引发局部放电并加剧绝缘材料老化,增大复合绝缘系统发生故障的概率,同时也给高压直流装备设计和制造带来新的挑战,制约高压直流输电等级和容量的发展。传统改善电场分布的措施存在各自的局限性。本文提出利用具有非线性电导复合材料,达到自行均匀电场分布的效果。以高压直流输电设备为应用背景,研究了环氧树脂/SiC复合材料非线性电导特性以及在直流盆式绝缘子和直流套管中的电场分布调控效果,以期为高压直流装备设计提供实验数据和相关理论支持。本文的主要研究内容和得到的结论如下:（1）使用物理共混法和热压成型法制备了掺杂不同含量、不同晶型的环氧树脂/SiC非线性电导特性复合材料,研究了各复合材料试样在不同温度下的非线性电导特性。研究结果表明:在相同温度下,随着微米SiC填料掺量的增加,环氧树脂/SiC复合材料试样的非线性电导特性逐渐增强,具体表现为非线性系数越来越大,非线性阈值场强越来越低。研究不同SiC晶型对复合材料试样非线性电导特性的影响时发现,在相同温度、含量及电场强度下,掺杂β-SiC的环氧树脂复合材料的非线性电导特性比掺杂α-SiC的复合材料效果更加明显,这是因为相同含量下棒状结构的β-SiC相比于球状结构的α-SiC更容易形成逾渗网络。研究不同温度对复合材料试样非线性电导特性的影响时发现,填料含量较低时,复合材料的导电机理主要为热激跳跃电导,电导率随温度升高显著增加;填料含量较高时,复合材料内SiC颗粒相互接触形成完善的逾渗网络,电导率对温度的敏感性下降。（2）使用非线性电导环氧树脂复合材料替代普通环氧树脂,并仿真分析了其在高压直流盆式绝缘子和换流变压器套管中电场分布的调控效果。结果表明:非线性电导环氧树脂复合材料的使用,可以显著降低绝缘子沿面最大电场强度幅值,起到均匀绝缘子沿面电场的作用;法兰处的套管芯子电场畸变得到了极大的改善,最大畸变场强下降了33%;套管端部的SF₆气体和变压器油内的电场强度也随之降低。在环氧树脂基体内加入微米SiC获得非线性电导的同时,也大大地提高了环氧树脂复合材料的电导率,运行中将引起更高的功率损耗,而与导杆的焦耳发热相比,非线性绝缘子和套管的损耗增加可以忽略。更多还原

【Abstract】 High voltage direct current(HVDC)power equipment is an important part of the system of long-distance and large-capacity power transmission and renewable energy consumption.However,the electric field distortion is widely existing in key equipment of HVDC transmission,not only causing partial discharge and aggravating the aging of insulation materials,increasing the probability of failure of the composite insulation system,but also bringing challenges to designing and manufacturing HVDC equipment and limiting the development of HVDC transmission grade and capacity.Conventional measures to improve the electric field distribution have their own limitations.It is proposed in this paper that using composite materials with non-linear conductive characteristics can smartly smooth the non-uniform electric field.With the purpose of providing experimental data support for the design of HVDC transmission equipments,this paper takes HVDC transmission equipment as application background and studies the non-linear characteristics of the epoxy resin(EP)/SiC composite materials and their effects on regulating the distribution of electric field when they are in HVDC basin spacer and converter transformer bushing.The main contents of this paper and the conclusions obtained are as follows:(1)The epoxy resin(EP)/SiC composite samples with different contents and different SiC crystal forms were prepared by physical doping method and hot press forming method.The non-linear characteristics of each sample under different temperature was studied.The results show that at the same temperature,as the content of micro-SiC increases,the non-linear characteristics of EP/SiC composite samples become stronger,which is characterized by the increasing non-linear coefficient and the decreasing non-linear threshold.The study of the effect of different SiC crystal forms on the non-linear characteristics of EP/SiC composite samples indicates that for the same temperature,SiC content and the electric field strength,the non-linear characteristics of EP/β-SiC composite samples are much stronger than those of EP/α-SiC composite specimens,because rod-shaped β-SiC at the same content is more li ely to form a percolation channel than spherical α-SiC.A study on different temperatures’ influence on non-linear characteristics of composite samples shows that when the content is low,the conductive mechanism is mainly the thermal shock jump conductance and the conductivity increases significantly as the temperature increases;when the content is high,SiC particles in the composite material contact each other to form a perfect percolation network,and the sensitivity of the conductivity to temperature decreases.(2)The non-linear epoxy resin composites were used to replace the common epoxy resin,and researched its effects on regulating the distribution of electric field on HVDC basin spacer and HVDC converter transformer bushing.The results show that the application of non-linear conductive epoxy composites can reduce the maximum electric field strength amplitude and uniform the electric field distribution along the spacer.When the bushing core is made of non-linear conductivity epoxy resin composites,the field distortion at the flange is improved,which also decreases the field strength in the SF6 and oil.Doping micro-SiC to the epoxy resin matrix to obtain non-linear conductance greatly improves the electrical conductivity of the epoxy resin composite,which will cause higher power loss during operation,but compared with the power loss of the guide rod,increasing loss of the non-linear spacer and the bushing is negligible.更多还原