Development of Smart Silicone Rubber Insulating Materials for HVDC Transmission Systems

硅橡胶绝缘子具有优良的防污性能，已在交流架空输电系统中取代传统的瓷绝缘子或钢化玻璃绝缘子。这些绝缘子也被推荐用于高压直流(HVDC)输电线路系统，在几何形状上做了一些改变，但没有考虑外壳材料的设计。通过增加爬电距离来修改几何形状可以在短期内确保可接受的闪络性能，但老化仍然是一个非常令人担忧的问题。随着高压直流输电线路在电网中的应用日益广泛，人们对开发用于高压直流输电系统的硅橡胶绝缘外壳材料产生了浓厚的兴趣。*传统硅橡胶外壳材料是基于交流绝缘子50多年的行业经验而开发的。但是，这种基于经验的方法不能应用于直流绝缘子的开发，因为在直流电压下绝缘子老化方面的经验有限。这项研究计划建议开发可靠、经济实惠的智能硅橡胶外壳材料，用于机械结构的直流户外绝缘应用。以下项目是在拟议的研究方案下执行的。*(1)腐蚀机制：硅橡胶绝缘子在外壳材料表面引起的干带电弧导致的腐蚀是导致绝缘在受污染的使用条件下失效的关键老化机制。为了建立干带电弧作为热源冲击表面并引起热烧蚀的电热模型，研究了直流与交流干带电弧的动态特性。*(2)无机填料的作用：传统上，外壳材料复合材料尽可能多地装载无机填料。无机填料作为阻燃剂，可以抑制由于干带弧化导致表面分解而形成的碳质痕迹。然而，硅橡胶是防痕迹的，因此腐蚀是一个令人担忧的问题。在本项目中，研究了无机填料的防冲效果。还将重点了解界面在使用纳米填料时所起的作用。因此，开发了一个热模型来预测使用无机填料配制的直流户外绝缘复合材料的冲蚀性能。*(3)材料筛选方法：针对绝缘子制造商和公用事业公司提出的巨大需求，开发了一种直流室外绝缘材料耐冲蚀性能鉴定的材料筛选方法，以提供与实际使用性能相关的可重复性的结果。

Silicone rubber insulators have shown excellent pollution performance and thus have been replacing the conventional insulators made from porcelain or toughened glass in alternating current (AC) overhead power transmission systems. These insulators are also recommended for use in high voltage direct current (HVDC) transmission line systems, with a few changes made in the geometry but with no consideration given to the housing material design. Modifying the geometry by increasing the creepage distance may ensure an acceptable flashover performance over the short term, but aging remains an issue of a great concern. In the light of the increased application of HVDC links in the electricity grid, this concern has driven an interest in developing reliable silicone rubber insulation housing materials for HVDC systems. *** Conventional silicone rubber housing materials have been developed based on more than 50 years of industry experience in AC insulators. But, this experience-based approach cannot be applied in the development of DC insulators as experience is limited in insulator aging under DC voltages. This research program proposes the development of reliable, cost-effective, and thus smart, silicone rubber housing materials for DC outdoor insulation applications in a mechanistic-based framework. The following projects are executed under the proposed research program. *** (1) Erosion Mechanisms: erosion of silicone rubber insulators as a result of dry-band arcing induced on the surface of the housing material is a critical aging mechanism leading to insulation failure in polluted service condition. The dynamic nature of the DC as compared to the AC dry-band arcing is studied in order to develop an electro-thermal model for the dry-band arcing as a heat source, impinging the surface and causing heat ablation. *** (2) The Role of Inorganic Fillers: Traditionally, housing material composites are loaded as much as possible with inorganic fillers. Inorganic fillers, as flame retardants, suppress the formation of carbonaceous tracks as a result of dry-band arcing causing decomposition of the surface. However, silicone rubber is tracking-resistant and thus erosion is of a concern. In this project, the erosion suppression effects of inorganic fillers are investigated. Emphasis will also be given to understand role of interface as nano-sized fillers are employed. Accordingly, a thermal model is developed to predict the erosion performance of composites formulated for DC outdoor insulation using inorganic fillers.*** (3) Material Screening Methods: In response to a great demand raised by insulator manufacturers and utilities, a material screening method for the qualification of erosion resistance of DC outdoor insulating materials is developed to provide reproducible outcomes that correlate with the actual performance in service.