Ceramic insulators, specifically porcelain and glass insulators, have widely been used all over the world since the 19th century [1,2]. However, when such insulators are energized and exposed to different pollution environments under different climatic and weather conditions, leakage current (LC) develops along their surfaces [3–7] and eventually cause flashovers. Various remedial measures have been adopted by power utilities to mitigate this problem. Among the common methods are: (a) increasing insulator creepage (leakage) distance, (b) reducing supply voltage, (c) insulator washing (cleaning), (d) oiling or greasing (silicone) the insulator surface, and (e) insulator replacement. Composite insulators, also referred to as non-ceramic or polymeric insulators, have also been used during the last six decades as an alternative to the ceramic insulators [8–10]. The housing materials most often used have been silicone rubber (SIR) [11] and ethylene-propylene-diene-monomer based rubber (EPDM) [12]. Water repellent (hydrophobic) properties of composite insulators, light weight, resistance to vandalism are among the main reasons for their usage. This has been proven by positive outcomes of numerous studies performed in laboratory and field conditions [8,9,13–16]. However, due to exposure to harsh service stresses such as corona discharges, UV radiation and chemical attacks etc., the housing materials may lose hydrophobic properties and develop surface degradation (tracking, erosion). In addition to the ever-increasing use of composite insulators, polymeric coatings (mainly RTV silicone rubber) [17] and semi-conducting glazes [18] have also been adopted for improving performance of ceramic and glass insulators [19].

中文翻译：

---

斯里兰卡热带条件下户外绝缘子的性能

陶瓷绝缘子，特别是瓷绝缘子和玻璃绝缘子，自19世纪以来在世界范围内得到广泛应用[1,2]。然而，当此类绝缘子在不同气候和天气条件下通电并暴露于不同污染环境时，泄漏电流 (LC) 会沿其表面产生 [3-7] 并最终导致闪络。电力公司已经采取了各种补救措施来缓解这个问题。常用的方法有：(a) 增加绝缘体爬电（泄漏）距离，(b) 降低电源电压，(c) 绝缘体清洗（清洁），(d) 给绝缘体表面涂油或润滑（硅胶），以及 (e)绝缘子更换。复合绝缘子，也称为非陶瓷或聚合物绝缘子，在过去的 60 年中也被用作陶瓷绝缘体的替代品 [8-10]。最常用的外壳材料是硅橡胶 (SIR) [11] 和基于乙烯-丙烯-二烯单体的橡胶 (EPDM) [12]。复合绝缘子的拒水（疏水）特性、重量轻、抗破坏性是其使用的主要原因。在实验室和现场条件下进行的大量研究的积极成果已经证明了这一点 [8,9,13-16]。然而，由于暴露于苛刻的服务应力（例如电晕放电、紫外线辐射和化学侵蚀等），外壳材料可能会失去疏水性并发生表面退化（起痕、侵蚀）。除了越来越多地使用复合绝缘子，