直流场下温度对硅橡胶电树枝起始特性的影响  

Influence of Temperature on DC Electrical Tree Initiation in Silicone Rubber

作　　者：周远翔[1] 陈明[1] 张云霄[1] 戴超[1,2] 陈铮铮 ZHOU Yuanxiang;CHEN Ming;ZHANG Yunxiao;DAI Chao;CHEN Zhengzheng(State Key Lab of Electrical Power System,Department of Electrical Engineering Tsinghua University,Beijing 100084,China;School of Electrical Engineering,Beijing Jiaotong University,Beijing 100044,China;State Grid Electric Power Research Institute,Wuhan 430074,China)

机构地区：[1]清华大学电机工程与应用电子技术系电力系统及发电设备控制和仿真国家重点实验室,北京100084 [2]北京交通大学电气工程学院,北京100044 [3]中国电力科学研究院有限公司,武汉430074

出　　处：《高电压技术》2018年第12期3784-3790,共7页High Voltage Engineering

基　　金：国家重点基础研究发展计划(973计划)(2014CB239501);国家自然科学基金(50877040)~~

摘　　要：直流电缆长期运行在高温下对电缆附件绝缘材料的电气性能有重大影响。为此选择新型超高压预制式电缆附件主绝缘材料硅橡胶作为研究对象,针对温度对硅橡胶材料直流电树枝起始特性的影响展开试验研究,在20、60、90和120℃下测定针尖完好和针尖有气隙两种硅橡胶试品的直流起树电压,并通过数字显微系统记录下电树枝形态。试验中观测到的硅橡胶直流电树枝形态仅有单枝状和树枝状两种。试验结果表明,针尖完好试品的平均起树电压随着温度的升高单调下降。针尖存在气隙时,起树电压明显比针尖无气隙时低,平均起树电压和树枝形态比例随温度变化均呈现出非单调的变化规律。试验中还发现,针尖有气隙试品的起树电压与二次起树电压基本一致。结合差热分析试验结果进行分析讨论后认为,温升引起硅橡胶局部链段松弛是温度场下硅橡胶直流起树电压下降的重要原因。温度对硅橡胶直流电树枝起始特性有显著的影响,因此长期运行在高温下的直流电缆系统性能势必会因此而受到影响,需要引起足够的重视。另外,针尖有气隙的试品可以模拟电缆中二次起树现象,为电缆二次起树电压的裕度设计提供了相应的理论依据。The operating temperature of DC power cable has a critical impact on the electrical performance of silicone rubber (SIR) in the new types of extra-high voltage prefabricated cable accessories. We conducted tests to reveal the relationship between temperature and DC electrical tree initiation characteristics considering different defect types. The DC electrical tree initiation voltage and electrical tree shapes were measured via a digital micro-imaging system under 20, 60, 90 and 120 ℃, respectively. Results show that only two shapes such as single-branch trees and branch trees can be observed under the DC conditions. In intact needle-tip specimens, it is found that average tree initiation voltage decreases monotonically with temperature increasing. In air gap crack and needle coexisting specimens, tree initiation voltage is obviously lower than that of intact needle-tip specimens. The average tree initiation voltage and proportion of electrical tree shapes both show non-monotonic trend as the temperature rises in SIR specimen with air gap defects. Furthermore, the tree initiation voltage in air gap crack and needle coexisting specimens is consistent with secondary tree initiation voltage. Combined with experiments of differential scanning calorimetry (DSC), it is concluded that partial segment relaxation of SIR due to the rise of temperature leads to the decrease of tree initiation voltage. More attention should be paid to temperature since DC power cable system has to operate for long time at high temperature which has great effects on the DC electrical tree initiation characteristics of SIR. Moreover, air gap crack and needle coexisting specimens can be used to simulate the secondary tree initiation, which provides a reference for cable insulation design.

关 键 词：硅橡胶 温度 缺陷 起树电压 电树枝形态 链段松弛 二次起树 

分 类 号：TM215.2[一般工业技术—材料科学与工程]