High Voltage Outdoor Insulators Research Articles

Electrical Properties of Silver-Silicone Rubber Nanocomposites for High-Voltage Outdoor Insulators

Electrical Properties of Silver-Silicone Rubber Nanocomposites for High-Voltage Outdoor Insulators

Investigation of SiO2/ATH/TiO2 Micro-nanofillers to Improve the Performance of Silicone Rubber for High Voltage Outdoor Insulators

Investigation of SiO2/ATH/TiO2 Micro-nanofillers to Improve the Performance of Silicone Rubber for High Voltage Outdoor Insulators

Effects of TiO2 nanoparticles and silane coupling agents on the adhesion strength and weathering properties of silicone rubber coatings

Environmental contamination on high voltage outdoor insulators can cause leakage currents and electrical flashover and finally reduce the reliability of electric distribution systems. To prevent energy losses and enormous damages, the in-service life of insulators has to be extended. For this purpose, room-temperature-vulcanizing (RTV) silicone rubber coatings are used due to their hydrophobicity. The objective of the current paper is to enhance the weathering resistance and proper adhesion of these coatings to the insulator. In the present study, adhesion improvement was achieved by adding titanium dioxide (TiO2) nanoparticles and silane coupling agents to the silicone rubber. The mechanical properties of nanocomposite coatings were characterized using the pull-off test method. Also, the water immersion method was employed to investigate the weathering resistance. The results revealed that adding TiO2 nanoparticles and silane coupling improved nanoparticle dispersion, adhesion strength, hydrophobicity, and weathering properties of RTV coatings.

Electrical Performance Study of 11kV Coated Porcelain, Coated Glass, and Polymer Outdoor High Voltage Insulators

The study in this paper investigates how contaminations and different types of pollutants affect the electrical performance of outdoor coated porcelain, coated glass, and composite insulators when subjected to an 11 kV AC voltage. The ceramic insulators (porcelain and glass) coating layer is assumed to be RTV silicon rubber material with a 0.5 mm thickness. The effect of these three pollution cases on the electrical performance were investigated using a commercial software called COMSOL Multiphysics based on the finite element method (FEM). The three pollution cases were uniform, non-uniform pollution, and water droplets. In the uniform pollution condition, the pollution layer over the surface of the insulators was assumed to be 0.5 mm; however, in non-uniform pollution condition, water patches with a thickness varying from 0.5 to 1.5 mm was used. In water droplets condition, hemispherical shapes were used to model water droplets with a diameter of 1 mm. Voltage, electrical field distributions, and dissipated power were computed along the creepage distance of the three insulators models. The simulation results indicated that for the uniform case, the lowest electrical field appeared on the silicon rubber insulator. For the non-uniform case, the electrical field distribution became more non-uniform for the three models. In the water droplets case, more fluctuations appeared in the metal end fittings where the water droplets were located. The analysis indicated that the maximum dissipated power was found to be for the coated glass. The obtained results showed that the silicon rubber insulator offered better performance compared with coated porcelain and glass. Coated porcelain offered better performance compared with the coated glass insulator.

Stoichiometry composition of nanofiller SiO2 and ATH to improve properties of silicone elastomer for outdoor high voltage insulators

Silicone elastomer (SE) has several advantages as an insulator material, light weight, dielectric, water repellent (hydrophobic), resistivity, thermal, mechanical and earthquake resistant properties compared to porcelain/ceramic and glass. However, the installation of outdoor insulators with tropical climate temperature exposure above 15 °C, high humidity and uv intensity during the day can degrade its properties which will shorten the life of the insulator. Studies towards improvements to improve the performance of SE insulators under certain conditions can be carried out by using the vulcanization method, formulating the stoichiometry of the filler material. The high-dose filler in SE will increase its mechanical strength and thermal stability, but it can reduce its dielectric properties and the molding process more difficult. Therefore, the purpose of this study was to determine the stoichiometric composition of SiO2 nanofillers and alumina trihydrate (ATH) nanofiller on SE to improve their properties as outdoor high-voltage insulators. Making test-material from silicone rubber resin RTV683 with a mixture of silica powder (20 nm) and ATH powder (20–30 nm). The stoichiometric ratio of resin, filler and hardener compositions varied (80–95: 5–20: 3–7.5). To determine its performance, the specimens were aged by immersing them in 25–50 °C water, artificially polluting and uv radiation the surface to simulate the influence of water diffusion and transfer hydrophobicity to pollution on the surface material. Measurement results before and after treatment indicated that the combination of SiO2 + ATH nanofiller with a composition of 10–15%wt improved the properties of ES such as hydrophobic (average contact angle of water drops > 90°), water absorption < 1.6%, relative permittivity εr < 5, mechanical properties (tensile strength) is 9.57–27.48 N/mm2, surface roughness 0.022–0.153 μm, breakdown voltage 14.8–19.3 kV/cm varies depending on stoichiometric nanofiller, mixing process, curing temperature (50 °C–90 °C) and curing time 2–24 h.

Studying Dielectric Losses of Serially Combined Silicone Rubber and Epoxy Resin

High voltage outdoor insulation systems are conventionally ceramics and glass with several advantages, such as proven in the field, excellent dielectric properties, durability, and long life. However, they are heavy, attract vandals and break easily, and they can lose their dielectric properties easily when subjected to high voltage transients, arcing, and surges. To curb this, polymer insulators are used because they have excellent dielectric properties, such as those of ceramics and glass, with the added advantages that they do not break easily and recover their lost dielectric properties after any electrical transients. Therefore, this paper investigates the dielectric properties of polymeric materials – silicone rubber (SR) and epoxy resin (ER). Some SR samples were manufactured in the laboratory, and others were obtained from the industrial manufacturer. All the ER samples were manufactured in the laboratory. The dielectric measurements were performed with the Insulation Diagnostics System. Within the measured frequency ranges, the dielectric losses of SR manufactured industrially differ from the laboratory-manufactured specimens. This is due to filler materials in the industrially manufactured samples. For the case of serially connecting the SR and ER, there was a higher influence of dielectric loss of SR than the ER, with some remarkable dielectric losses at some frequencies.

Image analysis of PDMS/ZnO nanocomposite surfaces for optimized superhydrophobic and self-cleaning surface design

Optimized superhydrophobic and self-cleaning nanocomposite surfaces were obtained by spraying surface modified ZnO nanoparticles (NPs) onto PDMS, using octadecylphosphonic acid and octadecanethiol as hydrophobic modifiers. In this study, it is the first time to our knowledge that surface parameters such as topography, morphology, superhydrophobicity, and self-cleaning are correlated to particle surface distribution and agglomeration parameters obtained by image analysis. The topography, morphology, and wettability of the surfaces were analyzed using atomic force microscopy, scanning electron microscopy, static contact angle (SCA), and contact angle hysteresis measurements. Image analysis was performed using the new enhanced graphical user interface of a previously self-developed Matlab® algorithm. Both hydrophobization methodologies increased the NPs’ surface coverage and the hierarchical rough structure formation on the substrates, resulting in more homogenous superhydrophobic self-cleaning surfaces. A higher coated fraction and lower degree of interconnected uncoated PDMS paths are correlated to an increase in SCA. The combination of a higher agglomerates fraction, lower agglomerate radius, and lower distance between agglomerates obtained for the surfaces with hydrophobized ZnO-NPs rendered self-cleaning surfaces. The observed correlations increase the understanding of the design and modelling of superhydrophobic self-cleaning PDMS/ZnO nanocomposite surfaces for use in high voltage outdoor insulators.

Mechanistic insights into the ageing of EPDM micro/hybrid composites for high voltage insulation application

In this work, we explore the mechanistic insights into the aging of EPDM based micro/hybrid composites under following environment namely acid rain, cryogenic temperature, high temperature and UV irradiation. Physical properties and cross-link density changes were measured before and after aging which confirms the degradation of EPDM samples under high temperature and UV environment. Surface properties were also measured for the samples under various aging conditions. High-temperature aging resulted in an increase in contact angle whereas, UV has led to a major loss in contact angle for all the samples. Based on the chemical changes predicted by FTIR and NMR we propose a photo-oxidative degradation mechanism under UV irradiation and the influence of nano-micro filler at cryogenic and high temperature aging. Surface morphology and dielectric property of the samples were found to undergo major changes under high temperature and UV aging which directly influences the electrical insulation property of the composite. Finally, the study gives insights into the factor affecting the shelf life of the EPDM composites which are exposed mainly under the mentioned environment for its application in outdoor high voltage insulation applications and can help in overcoming the aging issues mainly faced by polymer composites.

Performance of a nanotextured superhydrophobic coating developed for high-voltage outdoor porcelain insulators

We live in an era of striking advancements in various domains of science and technology, where separate fields and specializations are overlapping into new horizons. This cooperative approach is emerging rapidly in polymer science by employing the organic and physical chemistry, materials science, as well as electrical and mechanical engineering to collaborate and develop uniquely innovative materials. In outdoor high voltage power equipment, various problems such as flashover, rain, icing, pollution, and UV can compromise the performance of insulators thereby distorting the reliability of the entire system. Superhydrophobic coatings are sought-after candidates owing to their ultra-non-wettable, easy-to-clean, and anti-ice character. However, the performance of superhydrophobic coatings when they are subjected to high-voltage fields is still lacking sufficient research. Here, we aimed at designing a robust and novel non-fluorinated superhydrophobic coating in order to increase the effective life-span of high-voltage insulators by preventing and/or delaying the possible arcing and flashover driven damages. The electrical properties of the coating were investigated through various and comprehensive test methods. The coating showed high thermal and desirable weathering stability. Compared with bare porcelain in dry, wet, and polluted conditions, the superhydrophobic coating successfully increased the flashover voltage. Moreover, the superhydrophobic coating exhibited low leakage currents through the condensation test when exposed to high humidity conditions. With leakage currents of as low as 20 mA after three continuous steps of voltage increase, the superhydrophobic coating showed less tracking and erosion lines than the pristine coating in an adapted inclined plane test for thin films.

The durability of superhydrophobic and slippery liquid infused porous surface coatings under corona discharge characteristic of the operation of high voltage power transmission lines

Application of polyfunctional water-repelling coatings for high voltage outdoor power lines wires, insulators, and line supports recently gathered large interest due to their ability to substantially boost performance. Such functionalization can mitigate the accumulation of water precipitates and atmospheric pollutions, decrease leakage current, increase flashover and corona ignition voltage. However, harsh conditions concomitant to a high voltage such as high energy ions and electrons, high ozone concentration, UV radiation impose strict requirements on the durability of applied coatings. In this paper, we focus on the analysis of the durability of superhydrophobic coatings (SHC) and slippery liquid infused porous surfaces (SLIPS) under prolonged exposure to industrial grade alternating current corona discharge. Reported results show that in contrast to previously reported low resilience of polymer-based SHC, proper metal-based SHC withstands many hours of exposure without notable degradation. The obtained data on the stability of SLIPS under corona discharge show notable degradation related to the high rate of infused layer depletion. Overall, reported results broaden the understanding of the effect of corona exposure on functional materials and reinforce the optimistic view on the applicability of SHC and SLIPS coatings in the power transmission industry.

Analysis of Physical, Ocular, and Aquaphobic Properties of Zirconium Oxide Nanofilms by Varying Sputtering Pressure

A thin coating of zirconium oxide (ZrO2) is placed on outdoor high-voltage insulators to minimize air fouling. ZrO2 thin film coatings were deposited on glass substrates using a DC sputtering (reactive magnetron) technique with sputtering pressures ranging from 5 to 25 mTorr. Characterization of the deposited films was carried out utilizing approaches such as XRD, AFM, CAG, and spectrophotometer. Following the XRD peaks, when 15 mTorr is reached, the average crystallite size increases, after which it begins to decline. The wettability of the deposited thin layer is associated with the coarseness calculated by AFM. At 15 mTorr pressure, maximum aquaphobic is achieved (107.45°). At this pressure, the transmittance and bandgap were similarly determined to be 90% and 5.43 eV, respectively.

Self-Healing Silicones for Outdoor High Voltage Insulation: Mechanism, Applications and Measurements

This paper discusses the state of the art in the application of self-healing silicone-based materials for outdoor high-voltage insulation. Both the dynamic behavior of the dimethyl side groups of silicone rubber and the diffusion of a bulk siloxane to maintain low surface energy are respectively reported as intrinsic mechanisms responsible for the self-healing of silicone rubber. Localization, temporality, mobility, and the type of synthesis are the aspects defining the efficiency of the self-healing ability of silicone rubber. In addition, the deterioration of the self-healing ability with filler loaded into silicone rubber insulation housing composites is discussed. Taking the self-healing property into consideration among the other properties of silicone rubber insulators, such as tracking and erosion resistance, can be a useful design practice at the material development stage. Hydrophobicity retention, recovery, and transfer measurements are discussed as useful indicators of the self-healing ability of silicone rubber. Nevertheless, there remains a need to standardize them as design tests at the material development stage. The paper is intended to shed the light on the hydrophobicity recovery, a key material design parameter in the development of silicone rubber outdoor insulating composites, similar to the tracking and erosion resistance.

Influence of dispersing aids on nano alumina/micro aluminum tri hydrate filled silicone rubber composites for outdoor high voltage insulators

AbstractNano alumina and micro aluminum tri hydrate filled high‐temperature vulcanizing silicone rubber composites were prepared with dispersing aids of surfactant Triton™‐X‐100 (TX‐100) and silane coupling agent 3‐methacryloxypropyltrimethoxysilane (KH‐570), through an in situ modification technique. Fourier transform infrared spectroscopy (FTIR) and X‐ray diffraction (XRD) analysis were carried out to understand the effects of dispersing aids on the structural and crystallographic properties of composites. Scanning electron microscopy images of TX‐100 dispersed composites revealed the presence of several localized regions of agglomeration, whereas KH‐570 dispersed composites showed moderate dispersion. Measurements of volume resistivity demonstrated an increment of four decades for KH‐570 dispersed nanocomposite over TX‐100. Better compatibility between fillers and base matrix through KH‐570 was evident from the low loss factor values. Inclined plane tracking and erosion results were discussed in detail with leakage current analysis. The binary composite prepared with KH‐570 was observed to resist the detrimental dry band arcing and subsequent erosion by 2 h and 20 min over TX‐100 dispersed composite. Dry arc resistance and the formation of thermal pathways connecting micro and nanofillers were discussed in detail. FTIR analysis of ash generated after inclined plane tracking and erosion test confirmed the surfacing of added fillers. KH‐570 dispersed composites showed superior properties as compared to composites prepared with TX‐100.

Viability of Fillers in HTV Silicone Rubber in the AC and DC Inclined Plane Tests

The viability of fillers for inhibiting the dry-band arcing damage on high temperature vulcanized silicone rubber under the critical AC and the equivalent DC voltages of inclined plane test is investigated. Alumina tri-hydrate and ground silica are employed in the study as common fillers employed in silicone rubber formulation for outdoor high voltage insulation, and thermal analysis is applied in order to understand the protective mechanisms of the fillers. Filler volume effect plays a role in improving the erosion performance, and the dilution effect of water of hydration is shown advantageous for preventing progressive (directed) erosion. Dilution effect promoted with internal oxidation is found only notable at 50 wt% alumina tri-hydrate in this study. On the other hand, alumina tri-hydrate at 10 or 30 wt% may yield a porous residue, which is conducive to thermo-oxidation (combustion) and consequently erosion. The erosion suppression effects reported for the fillers in the composites employed in this study are found less viable under the equivalent DC as compared to the critical AC voltages of the inclined plane test. This study clarifies common perceptions about the viability of fillers in silicone rubber for AC and DC outdoor insulation applications.

Investigation of epoxy composites for outdoor insulation under accelerated ultraviolet exposure

Epoxy and its composites have shown remarkable properties to be used for outdoor high voltage insulation applications. However, outdoor environment that contains UV-A radiations deteriorates the organic structure of epoxy-based insulators. To analyze the surface degradation and chemical changes in structure due to UV radiations, neat epoxy (NEPOX), 15 wt.% epoxy microcomposite (EMC 15) and 5 wt.% epoxy nanocomposite (ENC 5) were prepared and subjected to a specially fabricated UV chamber under accelerated conditions. The samples were analyzed with visual inspection, STRI hydrophobicity classification, and Scanning Electron Microscopy (SEM) and Fourier Transform Infrared (FTIR) spectroscopy. The analyses confirmed the pattern of gradual degradation of surface structure due to the appearance of ester and carbonyl groups due to oxidation of hydrocarbon chains. FTIR peaks of C=O stretching at ∼1725.52 increased by 157.44%, 75.86% and 33.33% for NEPOX, EMC 15 and ENC, respectively. This shows that ENC-5 expressed better resistance against surface oxidation as compared to EMC 15 and NEPOX. Addition of fillers enhanced the chain intactness and nano filler performed even better due to greater surface area and surface energy.

Condition Monitoring of Outdoor High Voltage Insulators, Online and Offline Techniques: A review

Outdoor insulator plays a vital role in high voltage transmission and distribution system. The performance and properties of outdoor insulator may severely affect due to various types of pollutants. The failure of insulation in high voltage system results in loss of supply and a huge loss of electrical energy to distribution utilities. In order to reduce power losses and provide a reliable power transmission, selection and design of insulators is very important. To monitor the condition and performance of outdoor insulator in contaminated conditions an appropriate diagnostic technique is required. In this paper various online and offline techniques for conditioning monitoring of outdoor insulators are reviewed under different contaminated conditions. To maintain the healthy environment, the condition monitoring of power line insulators is an important requirement. There are number of techniques that have been introduced to fulfil this requirement. Each technique used at different contaminated condition have their own pros and cons. The findings indicate that the most important effect on the surface of the insulators based on the contamination on the surface leakage current and the flashover voltage. This paper will help in the selection and design of condition monitoring techniques for high voltage outdoor insulator.

Pollution Flashover Characteristics of High-Voltage Outdoor Insulators: Analytical Study

Pollution Flashover Characteristics of High-Voltage Outdoor Insulators: Analytical Study

Hydrophobic, dielectric and water immersion performance of 9000 h multi-stresses aged silicone rubber composites for high voltage outdoor insulation

Room temperature vulcanized silicone rubber (RTV-SiR) materials are broadly employed for high voltage outdoor insulation applications. Like other polymeric materials, such insulators degrade due to the multiple stresses caused by the environment. Therefore, for the investigation of multiple stresses presented in the environment such as UV radiations, salt fog, acid rain, heat, humidity, etc., a neat SiR, two aluminum trihydrate (ATH) filled composites of SiR (SMC1 and SMC2), one silica filled composite SiR (SMC3), and a co-filled composite (SMNC) having ATH and silica as fillers are fabricated and tested for 9000 h. After aging, the sample SMC3 and neat SiR show better hydrophobic behavior than the other samples. All the samples offer better leakage current suppression throughout aging. Dielectric breakdown strength (DBS) of SMC2 and SMC1 is measured better than their counterparts. Volume and surface resistivities of SMC1 remain the highest followed by SMC2 and SMC3. Scanning electron microscopy (SEM) results suggest that the surface of SMC2 retains excellent surface condition followed by neat SiR. SMC1, SMC2, and SMNC absorb higher water relatively after 24 h of immersion test whilst SMC1 and SMC3 exhibit a similar tendency after 2-h boiling test.

Prediction of Critical Flashover Voltage of High Voltage Insulators Leveraging Bootstrap Neural Network

Understanding the flashover performance of the outdoor high voltage insulator has been in the interest of many researchers recently. Various studies have been performed to investigate the critical flashover voltage of outdoor high voltage insulators analytically and in the laboratory. However, laboratory experiments are expensive and time-consuming. On the other hand, mathematical models are based on certain assumptions which compromise on the accuracy of results. This paper presents an intelligent system based on Artificial Neural Networks (ANN) to predict the critical flashover voltage of High-Temperature Vulcanized (HTV) silicone rubber in polluted and humid conditions. Various types of learning algorithms are used, such as Gradient Descent (GD), Levenberg-Marquardt (LM), Conjugate Gradient (CG), Quasi-Newton (QN), Resilient Backpropagation (RBP), and Bayesian Regularization Backpropagation (BRBP) to train the ANN. The number of neurons in the hidden layers along with the learning rate was varied to understand the effect of these parameters on the performance of ANN. The proposed ANN was trained using experimental data obtained from extensive experimentation in the laboratory under controlled environmental conditions. The proposed model demonstrates promising results and can be used to monitor outdoor high voltage insulators. It was observed from obtained results that changing of the number of neurons, learning rates, and learning algorithms of ANN significantly change the performance of the proposed algorithm.

Enhanced dielectric and thermal performance by fabricating coalesced network of alumina trihydrate/boron nitride in silicone rubber for electrical insulation

Silicone rubber filled with micron-alumina trihydrate (ATH) is a substantially used composite material for high voltage outdoor insulators. This article investigates the effect of nano-boron nitride (BN) addition on the dielectric, thermal stability and thermal conductivity of solely micron-ATH-filled silicone rubber by fabricating coalesced network of particles. Micron-ATH/nano-BN-filled hybrid silicone rubber composites are fabricated with a ratio of 30/0 wt% (ATH30), 29/1 wt% (ATBN1), 27/3 wt% (ATBN3), 25/5 wt% (ATBN5) and 23/7 wt% (ATBN7) using mechanical mixing and water bath sonication techniques. Results suggest that the hybrid batch of silicone rubber composites (ATBN) possess lower permittivity, dielectric loss, enhanced thermal stability and thermal conductivity relative to ATH30. ATBN1 offers low permittivity and dielectric loss values of 3.64 and 0.0086 at 1000 Hz relative to 3.87 and 0.0224 of ATH30, respectively. As far as thermal properties are concerned, ATBN5 emerges as the most promising candidate for electrical insulation with 31 and 200°C higher temperatures for 10 and 15% mass loss, whilst it has shown 20% higher thermal conductivity than ATH30.