复合绝缘子在强风下的伞裙动态及断裂机理研究

Composite insulator is the key apparatus of the UHV/EHV transmission lines, of which the reliability is the premise of the safety for long-term operation of the power grid. The excellent contamination performance decided the dominant status in outdoor insulation of northwestern power grid, however in recent years for the restriction of transmission corridors, the HV transmission lines had to cross several storm-wind areas or gaps, this situation challenged the reliability of common composite insulators in long-term operation. The statistics in power operation indicates that large amount of composite insulators faced with sheds fracture failure. The basic mechanism of this problem is that, the sheds were vibrated by strong wind, and the oscillation leaded to cycled stress concentration at root area of sheds, which finally induced the fatigue fracture failure. This research will focus on the electrical affects of cracks developed on the shed surface, the mechanism of fluid induced vibration of insulator structure, the mechanism of fatigue fracture failure of insulators and the anti-wind principles of composite insulator. Aim of this research is to build a general theory of sheds fatigue failure, to get the parameter control theory to resist sheds oscillation, and to provide a fundamental theory for the design or selection of composite insulators utilized in srong wind area.

复合绝缘子是超/特高压输电线路的核心部件之一，其长期运行的可靠性是电网安全运营的关键。复合绝缘子耐污性能奠定了其在西北电网外绝缘中的主导地位。近年来由于输电走廊的制约，高压输电线路必经多个风区和风口，此情况对普通复合绝缘子的长期可靠运行形成严峻挑战。电网运行数据显示，在部分强风地区已经出现大规模的绝缘子伞裙断裂故障。该问题产生的原因是，伞裙在强风的流体激振下，发生伞裙大幅度摆动问题，进一步导致伞裙根部承受循环应力作用，最终造成复合绝缘子伞裙断裂故障。本课题重点研究伞裙表面裂纹的产生对电气特性影响、伞裙结构的流体激振机理、强风下绝缘子伞裙断裂理论以及复合绝缘子结构的抗风机理。旨在形成强风下复合绝缘子伞裙断裂的理论体系，得出抑制伞裙摆动的结构参数控制理论，为强风区复合绝缘子设计、选型奠定理论基础。

随着西电东送的发展战略的实行，高压输电线路经过多个风区和风口，复合绝缘子伞裙在强风的流体激振下，发生大幅度摆动问题，进一步导致伞裙根部承受循环应力作用，最终造成复合绝缘子伞裙断裂故障。目前电网运行数据显示，在部分强风地区已经出现大规模的绝缘子伞裙断裂故障。.本课题重点研究伞裙表面裂纹的产生对电气特性影响、伞裙结构的流体激振机理、强风下绝缘子伞裙断裂理论以及复合绝缘子结构的抗风机理。.电气实验表明高场强区的伞裙根部微裂纹会导致放电问题。染污放电实验表明闪络电弧可以穿越贯穿性裂纹，单支绝缘子爬距损失最高达20.4%。.风洞实验研究表明，复合绝缘子伞裙结构在相对较低风速下会发生稳定的涡激振动，在相对较高的风速下会发生剧烈的流激摆动或严重形变。在涡激振动的风速区段内，绝缘子伞裙边缘部位的振动幅值较低且持续稳定，振动频率及涡脱频率锁定在伞裙固有频率附近。.通过有限元模态分析，得到伞裙的具体结构参数与固有频率相关性，确立抗风型复合绝缘子局部结构设计的参数范围，得到复合绝缘子抗风设计原则。据此，项目组完成了2个型号抗风型750kV复合绝缘子设计。4支实验样品的大伞裙固有频率、抗风性能均达到设计目标，试验结果证明了设计理论的可靠性。目前，抗风型750kV复合绝缘子已在设计风速39m/s～42m/s输电线路安全运行满一年。