Foam-based internal electrical insulation of hollow-core composite insulators (HCIs) is regarded as a superior solution to gases for not requiring continuous monitoring, with polyurethanes (PUs) being the main solution to date. Potential restrictions facing PUs as well as the need for higher dielectric strengths have prompted research activities into alternative foams. This work follows an extensive experimental and simulative approach to investigate the dielectric strength of a novel polymeric foam, known as dry syntactic foam (DSF). Seven different densities in two thicknesses are manufactured and tested under ac, dc, and lightning impulse (LI) voltages. Two finite-element (FE) models are created based on microscope images to reproduce electrostatic- and conduction-dominated voltage distributions and complement the experiments. Under ac and LI, the dielectric strength is found to rise with foam density, whereas no distinctive effect is observed under dc stress. The simulations indicate that under ac and LI, the highest electrical fields are reached uniformly inside gas pores and, that under dc, certainly arranged pores observe significant higher stresses. The ac and LI results are discussed according to Townsend discharges, whereas a mechanism based on a transient process is suggested for dc.

中文翻译：

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新型低密度聚合物泡沫在交流、直流和雷电冲击电压下的介电强度

中空复合绝缘子 (HCI) 的基于泡沫的内部电绝缘被认为是不需要连续监测的气体的优越解决方案，聚氨酯 (PU) 是迄今为止的主要解决方案。PU 面临的潜在限制以及对更高介电强度的需求促使人们对替代泡沫进行研究。这项工作遵循广泛的实验和模拟方法来研究一种称为干复合泡沫 (DSF) 的新型聚合物泡沫的介电强度。在交流、直流和雷电冲击 (LI) 电压下制造和测试了两种厚度的七种不同密度。基于显微镜图像创建了两个有限元 (FE) 模型，以再现以静电和传导为主的电压分布并补充实验。在 ac 和 LI 下，发现介电强度随着泡沫密度的增加而增加，而在直流应力下没有观察到明显的影响。模拟表明，在交流和锂下，最高电场在气孔内均匀地达到，而在直流下，当然排列的孔隙观察到显着的更高应力。根据 Townsend 放电讨论了交流和 LI 结果，而对直流提出了基于瞬态过程的机制。