Silicone Rubber Composite Insulators Research Articles

A method for simulating powdering of silicone rubber composite insulator in coastal areas

A method for simulating powdering of silicone rubber composite insulator in coastal areas

Failure analysis of in-service aged 11 kV silicone rubber composite insulators

Failure analysis of in-service aged 11 kV silicone rubber composite insulators

Analysis of Sheath Breakdown Induced by Air Gap at the Interface Between Hardware and Sheath of Silicone Rubber Composite Insulator on the Roof of High-Speed Trains

Analysis of Sheath Breakdown Induced by Air Gap at the Interface Between Hardware and Sheath of Silicone Rubber Composite Insulator on the Roof of High-Speed Trains

Assessing charge accumulation and flashover phenomena on silicone rubber surface exposed to salt-containing droplets under direct current voltage

In damp and salt-fog environments, silicone rubber composite insulators are prone to forming dispersed droplets that absorb airborne salt nuclei, leading to charge accumulation and potentially causing flashovers that threaten transmission line stability. Regrettably, these concerns have not yet received sufficient attention from relevant researchers. This study examines the surface charge accumulation and flashover characteristics of silicone rubber insulators with droplets of varying electrical conductivity. The droplets can fix charges, as the conductivity of droplets on insulator surfaces increases, the migration rate of surface charges accelerates, causing distortion of the electric field and a significant increase the area of high-density charge regions on the sample surface. Compared with dry surfaces, increasing the equivalent salt density of salt-containing droplets attached to the surface from mild to severe (with conductivity increasing from 800 μS/cm to 2800 μS/cm) leads to a 25 %-40 % increase in the average surface charge density. After adsorbing charges, the salt droplets shorten the discharge development path, making it easier to trigger interface discharge. Compared with dry surfaces, the average flashover voltage of the salt droplets is reduced by at least 30 %. This study offers valuable analysis on charge accumulation and flashover for silicone rubber insulators in salt-fog environments.

Study on Discharge of Silicone Rubber Composite Insulator Surface Attached with Water Droplets Based on Experiment and Electrostatic Field Simulation

In order to understand the effect of liquid droplets on the discharge of composite insulators, the discharge experiment of silicone rubber with water droplets attached to the surface was carried out in an artificial fog chamber. By measuring flashover voltage and taking discharge pictures at the same time, the relationship between flashover voltage and water droplet on silicone rubber surface was analyzed, and the influence of water droplet quantity, distance between water droplet, water droplet radius and water droplet conductivity on the flashover voltage of composite insulator was studied. The effect of water drop on the surface electric field of silicone rubber and the relationship between the surface electric field and flashover voltage were analyzed by using finite element analysis software. The results show that the flashover voltage is less than dry lightning voltage when there is water droplet on the surface of silicone rubber. The flashover voltage decreases with the increase of the number of water droplet, the decrease of water droplet spacing, the increase of water droplet radius and the increase of water droplet conductivity.

Evaluation of aging and degradation for silicone rubber composite insulator based on machine learning

Silicone rubbers (SIRs), as the main material of composite insulator sheds, have aging phenomenon for the long-term operation in the outdoor, which has an important impact on the performance degradation of composite insulator. Periodic examine and replacement of severely aged composite insulator is of great significance for the safe operation of power system. However, there is no clear standard to estimate the aging degree. In order to evaluate the degree of aging and degradation more accurately, the experimental test and analysis of the SIR sheds were carried out from three aspects: physical characteristics, chemical composition and electrical properties. The physical characteristic results show that the surface of the aging SIR will appear obvious holes and cracks, as well as hardening. Chemical composition results show that the internal composition of the continuous decomposition, while a large number of heavy metal elements accumulate in the pollution. The change of physical characteristics and chemical composition of SIR sheds may lead to the deterioration of electrical properties. According to the above results, the influence rule of measurement parameters and aging degree was obtained, and the key characteristic parameters of aging were summarized and extracted. Based on the characteristic parameters, a decision tree aging evaluation model is established for state evaluation. The accuracy of machine learning is 100% and 93.2% respectively. For the on-site application, early warning of moderately aged insulators and replacement of severely aged insulators are proposed in the on-site maintenance of SIR composite insulators.

Effect of superhydrophobic surface on the surface trap distribution of silicone rubber composites

In order to study the effect of superhydrophobic surface on the surface electrical properties of silicone rubber composite insulators, superhydrophobic sample and common sample were prepared. Their surface flashover voltage in high vacuum and their surface potential decay curve in air were measured. Analyzed their surface trap distribution characteristics. The experimental results indicate that changing the surface structure of silicone rubber composites will alter the distribution of surface traps. The energy level and density of deep traps in superhydrophobic sample are higher than those on common sample, which effectively inhibits the electron avalanche of the superhydrophobic sample and ultimately increasing the surface flashover voltage.

Review of Aging Evaluation Methods for Silicone Rubber Composite Insulators

Silicone rubber insulation material is widely used for the external insulation of power systems. During the continuous service of a power grid, it will be seriously aged due to the influence of high voltage electric fields and harsh climate environments, which will reduce its insulation performance and service life and cause transmission line failure. How to evaluate the aging performance of silicone rubber insulation materials scientifically and accurately is a hot and difficult issue in the industry. Starting from the composite insulator, which is the most widely used insulating device of silicone rubber insulation materials, this paper expounds the aging mechanism of silicone rubber materials, analyzes the applicability and effectiveness of various existing aging tests and evaluation methods, especially discusses the magnetic resonance detection methods emerging in recent years, and finally summarizes the characterization and evaluation technology of the aging state of silicone rubber insulation materials.

Study on Silicone Rubber Composite Insulator Modified by High-Energy Electron Beam Irradiation

The impact of high-energy electron beam irradiation on silicone rubber composite insulator is investigated in this article. It was discovered that as the irradiation dose increased, the related properties of silicone rubber increased first and then decreased, with the static contact angle increasing to 111.8°, the tensile strength increasing to 4.59 MPa, the tear strength increasing to 26.8 kN/m, and the crosslinking density increasing to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$7.09\times 10^{-{4}}$ </tex-math></inline-formula> mol/cm3, but the elongation decreasing. SEM observation revealed that silicone rubber was more compact after irradiation. attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS) studies revealed that when the irradiation dose increased, the irradiation of silicone rubber shifted from crosslinking to degradation, and a new Si(−O)4 structure formed. Considering comprehensive performances, 40–50 kGy is the optimal irradiation dose. This article can provide support for understanding the irradiation modification of silicone rubber materials for composite insulator and also guide the preparation method of new silicone rubber.

Characterization Method for the Swelling Effect of an Insulating Washing Agent on Silicone Rubber in Power Systems.

Insulating washing is a valid method to recover the electrical performance of silicone rubber composite insulators under accumulation contamination; however, its swelling effect may deteriorate the electrical and mechanical properties after live washing. The swelling effect of the insulating washing agent on the electrical and mechanical properties of silicone rubber and its mechanism were investigated by macroscopic and microscopic characterization methods. The results showed that the swelling degree of silicone rubber increased as the immersing time increased and the increasing trend gradually slowed down. The degradation in mechanical properties is much greater than that in electrical properties, and the tensile strength at break dropped greatly by 16.3% at 20 min of immersing. Physical defects such as holes and cracks were observed by scanning electron microscopy. The main and side chains were partially broken, and the inorganic flame retardant Al(OH)3 was decreased by Fourier transform infrared spectroscopy. The damage to the microstructure caused by the swelling effect under the action of the washing agent is the main reason for the decrease in the mechanical properties of silicone rubber.

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

AbstractWhen 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.

Research of cycloaliphatic epoxy resin and silicone rubber composite insulator interface based on four‐electrode system and temperature rise model

AbstractInterface degradation between mandrel and sheath can cause a decrease in insulation performance and mechanical strength of composite insulators. In this study, the interface ageing properties of cycloaliphatic epoxy resin and silicone rubber composite insulator were compared. A water diffusion test was adopted to simulate the composite insulator ageing in a hot and humid environment. A four‐electrode system was built to detect leakage current at different locations (mandrel, sheath and interface), which is an important basis for evaluating insulator performance. The ageing degree of insulator could be quantitatively characterised by leakage current change. It was found that the infiltrated moisture had a great effect on insulation performance. Based on the water absorption test result, the interface performance of two insulators was mainly influenced by their sheath sealing quality. As an auxiliary evaluation method, temperature rise during the test was recorded using an infrared camera. The experiment results showed that interface degradation was the main factor for the insulation performance decrease of silicone rubber composite insulators. However, insulation level reduction of the cycloaliphatic epoxy resin was caused by the wet sheath. In addition, a model for temperature rise of cycloaliphatic epoxy resin insulators was proposed based on good correspondence between sheath material and insulation. The model incorporated multiple processes such as ageing and heating of insulators, and it can predict the early temperature rise well.

Non-destructive aging evaluation of 500-kV field-serviced silicone rubber composite insulators with photothermal radiometry

In this article, a non-destructive photothermal radiometry (PTR) method is proposed to quantitatively evaluate the aging degrees of field-servicing silicone rubber composite insulators via a thermal diffusivity ratio and degradation layer thickness. A sensitivity analysis is performed to investigate the sensitivity of the PTR amplitude and phase to the thermo-physical, optical, and structural parameters of the aged silicone rubber composite insulators consisting of a degradation layer and a substrate layer. It is found that the PTR amplitude and phase are highly sensitive to the thermal diffusivity, effective infrared absorption coefficient, and thickness of the degradation layer as well as the thermal diffusivity of the substrate layer but are much less sensitive to optical absorption coefficients of the degradation and substrate layers and the effective infrared absorption coefficient of the substrate layer. Thus, parameters with high sensitivity coefficients are set as free parameters and determined by multi-parameter fitting the frequency dependences of the PTR amplitude and phase measured directly from the surfaces of the field-serviced silicone rubber composite insulators to a two-layer PTR theoretical model, while in the multi-parameter fitting, the parameters with low sensitivity coefficients are set as “known” parameters whose values are either measured separately or taken from literature. By doing so, the thermal diffusivity ratio and degradation layer thickness are accurately determined in a non-destructive way. Experimental results demonstrate that the thermal diffusivity ratio and degradation layer thickness determined by the proposed non-destructive PTR method are in good agreement with that determined by a conventional destructive PTR method, thus, proving the feasibility of the non-destructive PTR method for quantitative evaluation of aging degrees of the silicone rubber composite insulators being serviced in the high-voltage power transmission systems.

Study on influencing factors and laws of infrared temperature measurement of silicone rubber composite insulator

Silicon rubber composite insulator is favoured by power system because of its excellent anti-pollution flashover performance. Among them, the core rod is an important structural component to bear the mechanical load of composite insulator. In recent years, there have been many brittle fracture faults of composite insulators in China, which directly affect the reliability of transmission lines. The composite insulator is usually accompanied by abnormal heating during the aging process. As an effective live detection method, infrared temperature measurement can find the defects of composite insulator in time and reduce the occurrence of string breaking accidents. In this paper, by artificially simulating the abnormal temperature rise of composite insulator, infrared temperature measurement was carried out under the conditions of different observation distance, different observation angle, different sheath thickness and different heat source temperature, so as to explore the influencing factors and laws of infrared temperature measurement of composite insulator. The results show that due to the difference of heat loss, sheath barrier and radiation ratio in thermal radiation propagation, the measured temperature decreases and the absolute temperature difference increases with the increase of observation distance, sheath thickness and observation angle. The built-in heat source temperature increases the total internal heat, which can partially weaken the influence of sheath thickness on the measured temperature and significantly expand the difference caused by observation angle.

Study on aging index of mechanical and electrical properties of high temperature vulcanized silicone rubber

Composite insulators are affected by various factors in operation. With the increase of operation time, the shed of silicone rubber composite insulators will become hard and brittle. In this paper, it is found that the hardness of long-term silicone rubber shed meets the standard requirements. The tear strength, tensile strength, elongation at break, resistance to electric tracking and corrosion loss decrease significantly after 5-10 years of operation. The decline of silicone content on the micro surface and the escape of inorganic fillers are the reasons for the deterioration of macro performance. Finally, the evaluation system for aging performance of insulators is preliminarily established, according to the aging degree of insulator, operation and maintenance suggestions are proposed.

Influence of Sheath Radial Crack on Flashover Arc and Leakage Current of Roof Silicon Rubber Insulator for High-Speed Train

In this paper, three types of insulators with no crack, short crack, and long crack are taken as the research objects to evaluate the influence of the penetrating cracks on the 1 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">st</sup> sheath of the roof silicone rubber composite insulator of high-speed train on the flashover characteristics. The continuous voltage rising method is used to obtain the influence characteristics of the crack on the development process of the flashover arc. The constant voltage withstand method is adopted to compare the leakage current when the contamination degree is 0.1 mg/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . The test results demonstrate that the crack has no significant effect on the flashover voltage and flashover path, and the flashover arc can burn the edge of the crack. The peak leakage current of the three different tests ranges from 24 mA to 30 mA. Additionally, the development of leakage current can be divided into four stages: rising, continuous violence, falling, and oscillating. Moreover, the sequence of the apparent leakage current of the insulator is long crack insulator, short crack insulator, and the one with no crack. The acceleration of the rising stage of the leakage current increases with the increase in the crack length. Meanwhile, the sum of the time of the rising stage, continuous stage, and falling stage of the insulator with long crack is the smallest. The crack will distort the distribution of current density and the electric field intensity in the vicinity. The results can provide references for evaluating the influence of radial cracks at the edge of the sheath on the flashover characteristics and optimizing the design of the roof insulator sheath structure.

A Proposal for the Evaluation of HTV Silicone Rubber Composite Insulators.

This paper describes in detail a step-by-step methodology for obtaining specimens from the housing material (high temperature vulcanized (HTV) silicone rubber with aluminum trihydrate (ATH) filler) of composite insulators (finished products), for five well known and commonly used tests. The aim of the paper is to render practical clarifications and additions to the instructions for five tests on composite insulators provided by international standards. Additionally, the ranges of the results of these tests are presented. More specifically, shore A hardness measurement, tensile strength and elongation at break test, tear strength test, density measurement and inclined plane test were conducted on the housing material of ten, new, unaged medium voltage composite insulators made by six different manufacturers. The results of these tests are presented as a contribution to the existing knowledge and a comparative study of corresponding results of previous investigations is performed. The presented procedures for specimens’ preparation, as well as the results (arithmetical ranges), could be used as guidelines for future testing on the housing material (HTV silicone rubber with ATH filler) of composite insulators, either by researchers and manufacturers, during laboratory testing and material development processes, or by customers (distribution and transmission networks owners), during batch acceptance tests.

Analysis of the Influence of Silicone Rubber Aging on the Transmission Parameters of Terahertz Waves

In this study, a method for testing the aging of silicone rubber insulators using terahertz waves in the 0.17–0.22 THz frequency band is proposed, aiming at the problem of online non-destructive testing of the aging degree of composite insulators. The relationship between the aging degree of silicone rubber composite insulators and the relative dielectric constant was studied through first-principles calculations and molecular chain scission models. In addition, the electromagnetic model of the terahertz signal incident on the silicon rubber sheet was simulated and the relationship between the aging degree of the silicon rubber and the terahertz input return loss was obtained. Eleven insulator samples with different degrees of aging were selected. In these samples, the degree of aging was calibrated according to the degree of surface deterioration and the average partial discharge voltage. The terahertz return loss measurement experiment was performed after that. Finally, the results of experiment and calculation simulation were compared and the reliability of the relationship between the aging degree of the silicone rubber insulator and the terahertz input return loss was verified.

Aging characterization of 500-kV field-serviced silicone rubber composite insulators with self-normalized photothermal radiometry

Aging of silicone rubber composite insulators widely used in high-voltage transmission lines is a dynamic process starting from surface and gradually forming an aged surface layer with reduced thermal diffusivity. Based on the demodulation of the modulated infrared radiation signal and the subsequent data analysis, self-normalized photothermal radiometry (PTR) is used to quantitatively characterize the aging degree of field-serviced composite insulators. The ratio of the thermal diffusivity of the aged layer normalized by the substrate thermal diffusivity is proposed to characterize the aging degree to eliminate the influence of the wide variation of the initial thermal diffusivities of fresh silicone rubber composite insulators which are normally not known. Experimental results show that the thermal diffusivity ratio decreases and the aged layer thickness increases monotonically with the increasing field-service years, in consistent with the measurements of hydrophobicity class. The thermal diffusivity ratio and thickness of the aged layer are expected to be used as numerical indices for understanding the aging mechanism and estimating the remaining lifetime of silicone rubber composite insulators in field service.

Depth profiling of surface degradation of silicone rubber composite insulators by remote laser-induced breakdown spectroscopy

High-voltage silicone rubber composite insulators are widely used for outdoor insulation in power transmission lines. Silicone rubber, which is used as a housing material, gradually degrades with long-term use in the field. Therefore, to accurately determine the lifetime of composite insulators, it is essential to evaluate this degradation. This paper describes the results of depth profiling, which shows the change in the chemical composition caused by degradation, using laser-induced breakdown spectroscopy (LIBS). A remote LIBS system was constructed for application in in-situ degradation diagnostics. Field-aged insulators were irradiated with second harmonic Nd:YAG laser pulses at a distance of 10. The emission from the plasma was received by a telescope, and a spectroscopic analysis was performed. Energy dispersive X-ray spectroscopy (EDX) was performed for a comparative study. The emission intensity ratio of silicone to aluminum, which forms an alumina trihydrate filler, decreased by approximately 30% at the degraded surface compared to the undegraded bulk. A reduction in silicones at the degraded surface up to a depth of 300 was confirmed by LIBS and EDX measurements. These results show that remote LIBS using the ratio of silicone to aluminum as an index is a promising method for the in-situ diagnostics of composite insulators.