Silicone rubber insulators have been replacing conventional insulators made from toughened glass and porcelain in the power system, due to the non-wetting properties of silicone rubber insulation housing. However, silicone elastomers will eventually wet-out leading to leakage current and dry-band arcing giving rise to erosion of the silicone housing material, and eventually insulation failure. Well-established formulations of insulation housing composites have been developed and validated for erosion performance using the standard inclined plane tracking and erosion test, yet no such formulations have been developed and validated for DC. With the assumption that equivalent performance will be obtained, an adjustment to the creepage distance has been the measure taken in using the AC insulators for DC, without taking into consideration the differing aspects of the DC as compared to the AC dry-band arcing. This practice questions the existing DC insulators as an unknown entity that requires further investigation to ensure the reliability of the power supply. In addition recent demands have been raised to develop housing composites specifically for DC outdoor insulation, particularly with the increased interest in DC. It follows that developing a standard DC inclined plane tracking and erosion test is necessary for the development of more suitable materials for outdoor DC insulation applications. This thesis provides a thorough study of the DC dry-band arcing mechanism as opposed to the well understood mechanism of the AC dry-band arcing and provides a mechanistic understanding to the dry-band arcing leading to erosion as a foundation for the development of a standard DC inclined plane tracking and erosion test. To this end, the influence of inorganic fillers in silicone rubber on resisting erosion due to dry-band arcing is also presented, as an essential step towards obtaining more suitable silicone composite for DC outdoor insulation applications.

Composite insulators have been in service in electric power networks successfully for more than 40 years, and now up to the highest operating voltages. The present book extensively covers such insulators with a special focus on today’s prevalent material, which is silicone rubber. It includes a detailed description of the electrical and mechanical characteristics of composite insulators, their material properties, their design as well as typical applications and service experience. Particular attention is given to the mechanical behavior of long rod and post insulators, insulated cross-arms, interphase spacers and hollow core apparatus insulators. The state of the art on manufacturing procedures and the selection and dimensioning of the necessary power arc and corona fittings is presented as well as evaluation tests of “old” insulators, i.e. insulators after many years in service. The closing chapter deals with an up to date overview of test procedures and IEC standards. The selection and the contents of the various subjects covered in this book are based on the authors’ more than thirty years of experience with a renowned European manufacturer of composite insulators and string hardware. Their long and active participation in the relevant CIGRE and IEC working bodies adding to this experience. This book is therefore addressed to practicing engineers from electric utilities and the industry, as well as to academic professionals.

Explore the diverse electrical engineering application of polymer composite materials with this in-depth collection edited by leaders in the field Polymer Composites for Electrical Engineering delivers a comprehensive exploration of the fundamental principles, state-of-the-art research, and future challenges of polymer composites. Written from the perspective of electrical engineering applications, like electrical and thermal energy storage, high temperature applications, fire retardance, power cables, electric stress control, and others, the book covers all major application branches of these widely used materials. Rather than focus on polymer composite materials themselves, the distinguished editors have chosen to collect contributions from industry leaders in the area of real and practical electrical engineering applications of polymer composites. The books relevance will only increase as advanced polymer composites receive more attention and interest in the area of advanced electronic devices and electric power equipment. Unique amongst its peers, Polymer Composites for Electrical Engineering offers readers a collection of practical and insightful materials that will be of great interest to both academic and industrial audiences. Those resources include: A comprehensive discussion of glass fiber reinforced polymer composites for power equipment, including GIS, bushing, transformers, and more) Explorations of polymer composites for capacitors, outdoor insulation, electric stress control, power cable insulation, electrical and thermal energy storage, and high temperature applications A treatment of semi-conductive polymer composites for power cables In-depth analysis of fire-retardant polymer composites for electrical engineering An examination of polymer composite conductors Perfect for postgraduate students and researchers working in the fields of electrical, electronic, and polymer engineering, Polymer Composites for Electrical Engineering will also earn a place in the libraries of those working in the areas of composite materials, energy science and technology, and nanotechnology.

One of the very few books devoted to the chemistry, materials and processing of liquid silicone rubber The scientific literature with respect to liquid silicone rubber is collected in this monograph. The text focuses on the fundamental issues such as properties, curing methods, special materials, as well as the latest developments, and provides a broad overview of the materials used therein. In particular, materials and compositions for liquid functional rubbers are discussed. Methods of curing and special properties are also described, such as tracking and erosion resistance, adhesion properties, storage and thermal stability. Methods of curing are precision casting, hybrid additive manufacturing, peroxide curing, ultraviolet curing, liquid injection moulding, or hot embossing. The book includes applications including automotive and underwater applications, electrical and optical uses, as well as medical uses.

Polymeric insulators are now a common replacement for conventional porcelain and glass string insulators on overhead distribution and transmission lines. The use of this mature technology represents many advantages to the utilities; however, in polluted environments and those with high moisture levels in the environment, electrical discharges will develop on the surface of the insulation. In the long term, electrical discharges cause degradation of the polymer insulation in the form of electrical tracking and material erosion, and both are detrimental to the life of the insulation. Inorganic fillers are added to polymer materials to make the insulation more resistant to discharges, and at the same time, to lower the cost of the insulation. However, there is a limit to the amount of filler that can be added as the processability of the polymer compound becomes extremely difficult and expensive. Microfillers are extensively used to modify the physical properties of the polymeric matrix, and the properties of these composites are well known. On the other hand, nanofillers are being used in some insulating composites for reinforcement of mechanical properties; their electrical characteristics have shown inconsistency in the literature, and this is attributable to the non-uniformity of the filler dispersion. Most researchers agree that particle dispersion is critical in the development of nanocomposites for electrical insulation applications. If the nanoparticles are well dispersed, the electrical properties of these materials will be significantly improved. The main problem in using nanofillers is that the nanoparticles agglomerate easily because of their high surface energy, such that conventional mixing techniques are unable to break apart the nanoparticle aggregates. A secondary problem is the incompatibility of the hydrophobic polymer with the hydrophilic nanoparticles which results in poor interfacial interactions. In this thesis, the reinforcement of a silicone rubber matrix is successfully accomplished with the combination of microfiller, nanofiller, and a commercial surfactant. To improve particle dispersion, several techniques are available apart from mixing. This includes surface modification of the nanoparticles by chemical and physical methods by using surfactants. While surfactants are commonly applied to liquids, their use to disperse nanoparticles in compositions forming solid dielectric materials has not yet been reported. The findings in this thesis have shown that Triton X-100, a common surfactant, significantly aids in the dispersion of nanosilica and nanoalumina in silicone rubber. The main advantage of the surfactant is that it lowers the surface energy and the interfacial tension of the nanoparticles. This reduces agglomeration and facilitates the separation of the particles during mixing, thereby allowing improved dispersion of the nanofillers, as observed through Scanning Electron Microscopy (SEM). However, also shown in the thesis is that Triton X-100 cannot interact efficiently with all types of nanofillers. A high concentration of surfactant can also compromise the adsorption of the matrix polymer chains on the filler particles, so it is necessary to establish a balance between matrix adsorption and the dispersion of the particles. Mechanical properties such as the tensile strength, elongation at break, and hardness may also suffer from the use of excess surfactant. In addition, excess surfactant can lead to surface wetting properties different from composites containing none. Better wetting due to the migration of excess surfactant to the surface of the silicone may favour arcing in a wet environment. The current investigation shows that for a specific filler and concentration, an optimal concentration of surfactant provides good erosion resistance without adversely affecting the mechanical characteristics of the nanocomposite. Stress-strain and hardness measurements are done to investigate the surfactant's effect on the mechanical properties of the composites. The effect of the surfactant on the surface of the composites is analyzed with static contact angle measurements. The heat resistance of nanofilled silicone rubber is explored using an infrared laser simulating the heat developed by dry-band arcing. Also, several industry standard test methods such as salt fog and inclined plane tests are used to evaluate the erosion resistance of the filled composites. The results of all three tests confirm that the combination of microfiller and nanofiller with surfactant results in composites with improved erosion resistance to dry band arcing, with the exception of the case where calcinated filler is used in the formulation. In this thesis, the thermal conductivity is measured using a standard ASTM method and calculated using several theoretical, semi-theoretical, and empirical models. A thermal model developed in COMSOL Multiphysics and solved using a finite element method (FEM) shows a temperature distribution in the modelled nanocomposites which is comparable to the temperature distribution measured with an infrared camera under laser heating. In addition, this investigation aims to define the mechanism by which the nanofillers improve the heat and erosion resistance of the silicone composites. In order to understand this mechanism, nano fumed silica, nano natural silica, and nano alumina are used in a silicone rubber (SiR) matrix in order to study the thermally decomposed silicone and the residual char that is formed during laser ablation tests. The white residue remaining after laser ablation on the surface of composites with fumed silica, natural silica, and alumina is analyzed in a number of ways. Scanning Electron Microscopy, Energy Dispersive X-ray analysis (EDAX), and X-ray diffraction (XRD) techniques are used to analyze the thermally decomposed silicone residue after laser heating indicating that the protective mechanism of the three analyzed nanofillers - fumed silica, natural silica, and alumina - appears to be the same. The formation of a continuous layer on the surface behaves as a thermal insulator protecting the material underneath from further decomposition.