Development of Functional Dielectrics for Future All-Solid Substations

随着未来全固态变电站的发展，功能型变电站已成为研发的目标。聚合物纳米复合材料被选为这样的功能材料。发现这些材料在热、机械和电性能方面比未填充的聚合物以及常规的微填料填充的聚合物更有利。研究的材料包括聚酰胺/层状硅酸盐纳米复合材料，环氧树脂/层状硅酸盐纳米复合材料，环氧树脂/二氧化钛纳米复合材料，环氧树脂/氧化铝纳米复合材料。通过SEM、AFM、XRD、Surface Roughness Meter、EDX等手段对材料进行表征，并对其在局部放电和高局部电场作用下的降解过程进行了研究，取得了如下成果：1.纳米填料与周围聚合物基体的界面是决定纳米复合材料性能的关键。从理论上提出了多核模型作为相互作用区的精细结构。研究发现，聚酰胺/层状硅酸盐纳米复合材料的抗局部放电性能远高于未填充的聚酰胺和微填料填充的聚酰胺。这是首次发现纳米复合材料的优点，并在世界范围内开展了此类研究。4.已经开发了一种独特的制备方法，在实验室规模制备纳米复合材料，特别是环氧树脂纳米复合材料。5.环氧树脂纳米复合材料不仅具有优异的局部放电电阻，而且还具有抗树枝化能力。这些发现可以用所提出的多核模型来解释。6.纳米结构使介电常数降低，而微填料填充聚合物使介电常数增加。它清楚地表明，界面深深参与确定宏观参数。

With future all-solid substations, functional dielectrics have been targeted as R & D. Polymer nanocomposites were chosen as such functional dielectrics. These materials were found to be much advantageous over unfilled polymers as well as conventional micro-filler filled polymers in thermal, mechanical and electrical properties. Materials investigated include polyamide/layered silicate nanocomposites, epoxy/layered silicate nanocomposites, epoxy/titania nanocomposites, and epoxy/alumina nanocomposites. Materials are characterized by SEM, AFM, XRD, Surface Roughness Meter, EDX and the like, while they are subjected to partial discharge and high local electric field to degrade.Some of the outstanding results are summarized as follows :1.Interfaces between nanofillers and surrounding polymer matrices are crucial to determine the properties of nanocomposites. Those form an interaction zone in mesoscopic scale.2.A multi-core model is proposed as fine structures of the interaction zone from theoretical consideration. Typically it consists of three layers, i.e. the first kyer, the second layer and the third layer from the contact point toward the matrices.3.It was found firstly that polyamide/layered silicate nanocomposites are far more resistant to partial discharges than unfilled polyamide and micro-filler filled polyamide. This is the first discovery of nanocomposite advantage to have initiated such studies worldwide.4.A unique manufacturing method has been developed to prepare nanocomposites in laboratory scale, especially epoxy nanocomposites.5.Epoxy nanocomposites exhibit not only excellent partial discharge resistance but also treeing resistance. These findings can be explained in term of the proposed multi-core model.6.Permittivity decreases due to nanostrucuration as our surprise, while it increase for micro-filler filled polymers. It clearly shows that interfaces are deeply involved to determine macroscopic parameters.