Radiation processing of polymer insulators: A method for improving their properties and performance

Polymer insulators for electric apparatus and high-voltage overhead lines are promising for replacing porcelain and glass insulators. The possibility of this application is shown by radiation-chemical technology for the manufacture of rodshaped polymer insulators. An ethylene and vinyl acetate copolymer (EVA) was used as the basis for polymer insulators. The composition also contains aluminium hydroxide as a filler and N,N′-m-phenylene dimaleimide as a sensitizer. The investigation of γ-radiation-induced crosslinking of this composition made it possible to establish the following optimum conditions of radiation processing of insulators: the absorbed dose of up to 200 kGy at a dose rate of 10 kGy/h in air. By forming a three-dimensional network in the polymer bulk by radiation, the service properties of the insulators are improved: Shape and heat stability is >200°C and the stability to tracking and erosion >200 h. Differential scanning calorimetry (DSC) and a method of stress relaxation were used in evaluation. In the Saint Petersburg region (Russia), several types of high-voltage (10–110 kV) polymer insulators are manufactured with the application of such radiation-chemical technology.     

Superhydrophobic Coatings for Improved Performance of Electrical Insulators

Dielectric strength of electrical insulators is adversely affected by both wet conditions and surface roughness due to accelerated dielectric breakdown. While textured superhydrophobic coatings (i.e., coatings that are extremely repellent to water) can prevent the accumulation of water and help retain the dielectric strength of insulators under wet conditions, it is unclear whether or not the presence of texture (i.e., surface roughness) allows the retention of the dielectric strength of insulators. In this work, through a series of systematic experiments and analysis, it is concluded that porous superhydrophobic coatings rather than rough monolithic superhydrophobic surfaces allow the retention of dielectric strength of insulators under wet conditions in spite of the surface roughness. The insights from this work can enable the design of electrical insulators with improved performance and increased longevity.     

An Improvement of the Technology of Continuous Molding of Ceramic Insulators with Spiral Ribs

New technical solutions in the technology of molding rod insulators with spiral ribs extruded from a vacuum press are considered. Positive results are obtained in a comparative trial of the insulators with spiral and ring ribs.     

TEMPERATURE OF PYREX AND PORCELAIN IN SUNLIGHT1

The relative temperatures of Pyrex glass insulators and porcelain insulators in sunlight are determined in three ways. A computation using the radiation and convection heating equations gives a value of 93 °C as a maximum surface temperature of porcelain in sunlight, with an assumed shade temperature of 40°C. In a similar way 46.5° C was determined for the Pyrex insulator. Measurements are given of the rise in temperature under natural conditions of Pyrex and porcelain insulators mounted on pins. Temperature measurements were made by means of thermocouples cemented to the surface of the insulators. Extreme conditions were further obtained by means of tin reflectors. Under such conditions the experiments show that the temperature of the porcelain insulator increases on the average about three and one-half times that of the Pyrex glass insulator.     

Microstructural and mechanical characterization of high strength porcelain insulators for power transmission and distribution applications

Porcelain insulators have prodigious importance in electricity transmission and distribution network because of their high dielectric constant, electrical resistivity, and mechanical strength and these properties are closely connected to the microstructural details of the insulator. Three different porcelain insulators (Sample A, B and C) were reported in the present work. X-ray fluorescence (XRF), X-ray diffraction (XRD), scanning electron microscopy (SEM), three point bending test and density and pore analysis were carried out to investigate the structural and mechanical properties of various insulators. The analysis confirmed that the porcelain insulators are made of industrial alumina, quartz, clay, and feldspar having amorphous as well as crystalline phase in the body. The porosity, density, and bending strength were also calculated and a correlation was developed between mechanical strength of the insulator and various physio-chemical and microstructural properties. Sample A showed the highest value of bending strength i.e. 207.20 MPa and sample C the lowest value of 112.18 MPa while sample B demonstrated the intermediate value of 170.98 MPa. To formulate high strength porcelain insulators, it was concluded that the amount of amorphous phase, dispersed corundum, and mullite content are key factors to control the mechanical strength of porcelain insulators.     

合成绝缘子在电气化铁道接触网上的应用和发展

介绍了合成绝缘子在电气化铁道接触网的国内外应用情况 ,探讨了它们的发展趋势 ,指出了在我国大力发展电气化铁道接触网专用绝缘子的必要性和可能性 ,以及研究开发这种产品应注意的一些问题     

EXTRUSION OF REFRACTORY OXIDE INSULATORS FOR VACWM TUBES1

A method is described whereby nonplastic materials such as refractory oxides are given a temporary plasticity, sufficient for extrusion. The organic plastic gel used consists of flour or starch paste with ammonia as an electrolyte. A short detailed account is given of the manufacture of twin-hole insulators made of MgO 98% and talc 2% for radio 227 vacuum tubes, with supplemental experimental results on other materials. The refractory oxides Al₂O₃, BeO, ZrO₂, MgO, and ThO₂ are compared from the standpoint of their physical properties and their ability to act as insulators in contact with hot tungsten filaments. Examples are given of the use of such extruded oxide insulators for hot filament supports.     

Structural homogenization in a fibrous insulator containing an inorganic binder

Conclusions Ammonium salts can be used as flocculants to prevent colloidal particles of the inorganic binder (silicic acid sol) from migrating to the outer layers of fibrous insulators during heat treatment.Measurements have been made on how the additives affect the major parameters for mullite-silica insulators.The additives provide structural homogeneity, where the binder content per unit volume deviates by not more than ±3% from the mean; the compositions after heat treatment are the same as those of items made with pure silica sol, but the major working characteristics are improved.The additives do not require any change in the standard slip technology for making these insulators.Translated from Ogneupory, No. 5, pp. 21–23, May, 1989.     

Nanostructured insulators – A review of nanotechnology concepts for outdoor ceramic insulators

Nanotechnology is rapidly growing as a new technology alternative to create advance materials with unique characteristics and performance for different applications in several industrial sectors. In recent years, many nanotechnology-based products have appeared in our everyday life. On the other hand, industries have also considered nano-concepts to produce high-added value products with superior capacity, reliability and efficiency. Electric insulators are components with high importance in the electricity network system; reliability and high performance are essential characteristics demanded by actual markets. Recent studies have demonstrated the technical feasibility of innovative nano-concepts to improve the final properties of these electrical components. This paper reviews the state-of-the-art of nanotechnology applications for outdoor insulators. Nano-concepts for ceramic insulators are summarized and reported with the aim to provide an overview of applications and opportunities for electric industry. In addition, the future trends and challenges for this field are also considered in this work.     

New Effective Ways Toward Solving the Problem of Contamination of Porcelain Insulators

The use of special coating organic materials for imparting hydrophobic properties to the surface of high-voltage porcelain insulators exposed to environmental contamination is described. The surface hydrophobization technique makes it possible to improve the electric performance of insulators and prevent current leakage under industrial conditions and opens ways toward designing insulators safe against flashover and insulation assemblies resistant to aging.     

The search for optimum solutions for melting insulator glass

The effect of the temperature conditions of melting and the design features of the glass melting furnaces on the increase in the specific removal of glass melt in processing quenched insulating parts of high-voltage suspension insulators is demonstrated. Designs are proposed for glass melting furnaces and glass melting temperature regimes whose use will increase the economy of manufacturing insulators.     

Inorganic salt assisted high temperature hydrothermal synthesis of ordered mesoporous silicas with enhanced stability and ultralow dielectric constants

Journal of Porous Materials - The thermal insulators with extraordinarily ultra-low dielectric constants (k?<?2.0) show great application potentials of superior insulators in...     

Effect of CeO2 on UV aging of composite insulators prepared by template-spraying method

When the silicone rubber composite insulator is exposed outdoors for a long time, it will be affected by high-temperature ultraviolet environments. In order to ensure the operation of silicone rubber composite insulators, a super-hydrophobic composite insulator with antiaging characteristics was prepared by mixing cerium dioxide (CeO₂) with silicone rubber and spraying CeO₂ on the surface of silicone rubber. This article studied the aging characteristics of the base and surface of silicone rubber composite insulator by CeO₂ in ultraviolet environment. The properties of silicone rubber composite insulators before and after aging were tested by mechanics, contact Angle, rolling Angle, bounce, and icing experiments. The aging mechanism of silicone rubber was analyzed by Fourier transform infrared spectroscopy and search engine marketing. This study prepared composite insulators with excellent mechanical, hydrophobic, and antiicing properties. The aging resistance of silicone rubber composite insulators is improved by adding CeO₂ into silicone rubber matrix and spraying CeO₂ on the surface, which also ensure the use of composite insulators in high-temperature ultraviolet environment.     

Fabrication of Highly Porous Silica Thermal Insulators Prepared by Gelation–Freezing Route

Highly porous silica thermal insulators were produced by gelation of a gelatin solution with dispersed silica particles, followed by freeze‐drying and heating at 800°C. The relationship between the ice‐template morphology and the parameters involved in gelation freezing was investigated, in addition to the effect of the microstructure on the thermal conductivity of the silica insulators. The porosity and thermal conductivity of the insulators ranged from 88 to 98 vol% and from 0.168 to 0.054 W (m·K)^?1, respectively, both of which could be controlled by changing the silica content in the gel stage. Gelation–freezing route was proved to be a feasible and promising route for the production of very highly porous, machinable insulators.     

Electron‐ and X‐ray‐induced electron emissions from insulators

The electron emission yields of insulators irradiated with ultra‐short pulsed X‐ray and electron beams differ significantly from those of metals. The main experimental results are reviewed and it is shown that the use of simple models for the transport and for the escape of the generated secondary electrons accounts for the role of the temperature and of the crystalline state on these yields (besides the role of the chemical composition of the insulator of interest). When permanent irradiation is used, charging and damaging effects occur and correlated mechanisms are then considered. The present analysis concerns a wide variety of insulators (from oxides and halides to polymers) investigated with a wide variety of techniques (XPS, AES, SEM, etc.) and various practical consequences are also deduced. © 2001 Society of Chemical Industry     

高压支柱瓷绝缘子冷热试验时炸坯原因的探讨

分析了高压支柱瓷绝缘子冷热试验时炸坯原因，并介绍了用调整球磨时间、末端螺旋角度等几种方法来解决高压支柱瓷绝缘子的冷热炸坯问题。     

环氧复合绝缘子APG制造工艺分析

主要阐述了环氧复合绝缘子的自动压力凝胶(APG)工艺技术,重点分析了APG工艺对环氧材料和模具的要求、材料预处理及成型温度和压力设定,并提出了环氧复合绝缘子在制造中常见的环氧固化收缩和开裂常见缺陷的原因与解决对策。     

锰铬体掺杂对氧化铝陶瓷绝缘子性能的影响

为改善氧化铝陶瓷绝缘子的沿面耐压能力开展体掺杂实验研究。以95％(质量分数,下同)氧化铝陶瓷瓷料为基料,选择Cr2O3和MnCO3作为添加剂制备掺杂样品,并对该陶瓷样品进行了性能参数测试及沿面耐压、体击穿、金属化等实验研究。结果表明：与目前常用的95％氧化铝陶瓷相比,锰铬掺杂氧化铝陶瓷具有更优越的表面性能。同一条件下,掺杂样品沿面耐压能力更强。采用新设计金属化配方及工艺,锰铬掺杂瓷样品金属化效果更佳。同时,体掺杂对氧化铝陶瓷体性能(体耐压水平、抗折强度等)没有十分明显的影响。进一步分析表明：锰铬掺杂降低了氧化铝陶瓷的表面电阻率和表面二次电子发射系数,从而使其具有更强的沿面绝缘能力。此外,在对陶瓷样品组成结构分析的基础上,就锰铬掺杂对氧化铝陶瓷的改性机理进行了探讨。     

High-Voltage Electric Insulators Based on Wollastonite

The possibility of using high-quality finely milled wollastonite in the composition of engineering ceramics is considered. The firing conditions, structure, and physicomechanical parameters of obtained electric insulators are determined.     

A Novel Application of Nano Anticontamination Technology for Outdoor High-Voltage Ceramic Insulators

A novel application of a nano-sized titanium dioxide (TiO₂) photocatalyst for improving the performance of the ceramic insulator under contaminated conditions is proposed in this paper. The TiO₂-coated insulator was prepared by spraying a certain amount of TiO₂ sol on the ceramic insulator followed by subsequent calcination. The physical and chemical properties of the TiO₂ film were studied and their influences on the self-cleaning and electrical performances of the ceramic insulator were evaluated. Compared with the uncoated insulators, the as-prepared TiO₂-coated insulator exhibited an enhanced self-cleaning ability in a heavy polluted environment because of the excellent photo-induced catalytic performance of the TiO₂ film. Moreover, the TiO₂-coated insulators presents a flashover voltage level similar to normal ceramic insulators, and even a higher performance of wet flashover than the latter. It was proposed that the semiconducting property and the hydrophilicity of TiO₂ films could be responsible for the promoting effect on the electrical performances of the porcelain insulator. This study shows that coating TiO₂ films on the surface of insulators may have a promise in preventing pollution flashover.