Insulator Surface Research Articles

Study of operation of a polymer insulator under uniform and non-uniform contamination

RELEVANCE. Suspended insulators, the technical condition of which largely determines the reliability of power supply to consumers of different categories, are one of the most damaged elements of overhead power transmission lines [1-2]. This is primarily due to the fact that during their operation, insulators are exposed to various climatic conditions that have a direct impact on their insulating properties. Moreover, precipitation, such as rain, fog or dew, has the greatest impact precisely in combination with various solid, liquid and gaseous particles deposited on the insulator surface from the air, and forming a layer of surface contamination. Wetting this layer increases the electrical conductivity of the entire overhead line insulation structure and reduces its insulating capacity. Study of influence of dampening of contaminated surface of suspended insulation on their discharge characteristics is an urgent scientific task. The solution of this task enables to develop the existing understanding of the mechanisms of formation and development of discharges on the contaminated and wetted surface of insulation and to formulate the appropriate diagnostic attributes applicable to control the condition of the overhead power line insulators. OBJECTIVE. To carry out laboratory research aimed at studying the behavior of suspended high-voltage polymer insulators of overhead power lines when they are moistened. To formulate appropriate diagnostic attributes applicable for control of condition of suspended insulators of overhead power lines during their operation. METHODS. At the solution of the posed problem experimental methods of research, consisting in simulation of work of the contaminated polymeric insulator in the atmosphere of a pure fog with application of the special experimental installation developed by the authors of this article were applied. RESULTS. As a result of laboratory research, by continuous registration of leakage current values, as well as signals coming from the remote sensor, characteristic features of contaminated insulator humidification were revealed, which can be used as diagnostic signs in the process of their operation.

Thermal parameter inversion of low-heat cement concrete for Baihetan arch dam

For the first time, low-heat cement was used in the entire dam section of Baihetan Dam, but the thermal properties of low-heat cement under construction conditions have yet to be fully studied. The thermal parameter values of low-heat cement may differ significantly from the indoor test values or specification values due to factors such as ambient temperature, cooling through water, and surface insulation under actual site conditions. Therefore, in order to obtain more accurate values of the thermal parameters, the hybrid swarm intelligence algorithm and field temperature monitoring data are used to identify the concrete thermal parameters of Baihetan arch dam. To overcome the shortcomings of Particle Swarm Optimization (PSO) that is easy to fall into local optimum and Artificial Bee Colony (ABC) that has insufficient development ability, an Integrated Algorithm Based on ABC and PSO (IABAP) is established. Through eight different test functions and comparing with other different algorithms, it is verified that the IABAP algorithm has certain advantages in terms of convergence speed and accuracy. Considering the influence of ambient air temperature and multi-shift water cooling during construction, IABAP is applied to the inversion of concrete thermal parameters with the same strength, different strength and different gradation of Baihetan arch dam. The computational results show the good performance of the IABAP algorithm in engineering applications on the one hand, and the applicability and reliability of the parameter inversion on the other hand, which can meet the accuracy requirements of practical engineering. At the same time, the conjecture that the thermal parameters are consistent in adjacent dam sections was verified by bringing the thermal parameters into the adjacent dam sections for simulation calculations. Finally, the experimental values of thermal parameters of low-heat cement concrete of Baihetan Dam were compared with the inverse values to analyze the change law of thermal parameters, and it was found that the final adiabatic temperature rise of low-heat concrete was smaller than the indoor experimental values during the actual construction.

Flexible smart surface coating for GIS/GIL epoxy insulators

AbstractA flexible smart coating with electroluminescence effect was designed and fabricated on the surface of gas insulated switch gear (GIS)/gas insulated transmission line (GIL) epoxy insulators based on two‐step curing process. As the AC voltage increases, the luminous area on the insulator surface expands from the centre to the periphery, and the light intensity shows a linear relationship with the applied voltage. Besides, the flexible smart coating can effectively identify the location of metal particle defects and the degree of electric field distortion. The flexible smart coating enhances the surface flashover voltage due to its higher dielectric constant. Simultaneously, metal particle contamination can substantially reduce the insulation performance of epoxy insulators, particularly when they are located near the high‐voltage side. It is hoped that this study can provide a reference for the smart detection of surface defects GIS/GIL basin insulators.

EXPERIMENTAL AND COMPUTATIONAL STUDY ON THERMAL PERFORMANCE OF WOOD-PLASTIC COMPOSITES IN BUILDING ENVELOPE

Wood-plastic composites (WPCs) are attractive material for enhancing thermal performance of buildings by acting as an insulation surface. A fast and reliable experimental method was devised using a simple quasi-steady heating film (QSHF) method to measure the thermal conductivity of locally manufactured WPCs in Kuwait. QSHF used two blocks of standard materials compared with the classic methods, although it does not require a fixed constant heating source nor a cooling source. QSHF had a 10 cm × 10 cm × 0.5 mm silicon heating film controlled by a temperature controller and several transparent acrylic square blocks of the same size with 10 mm thickness as the standard materials. The top surface of the WPC samples was the cold side of the system, which is open to indoor temperatures of 22-23°C. The bottom layer can be maintained at any desirable temperature ranges from 25° to 55°C using the heating film to simulate the real outdoor environment. The thermal conductivities of locally manufactured WPCs type, namely FB16, FB18W, CD, and TD, were 0.0912, 0.1174, 0.3453, and 0.3078 W/m.K, respectively, obtained within 1 to 3 hours, which all fall below the standard value of 0.414 W/(m<sup>2</sup>.K) for composite walls and 0.1-0.2 W/m.K for wood. Multiphysics CFD simulation for DP45 sample and TRNSYS simulation for FB18W WPC in the building envelop were conducted which showed strong 2D effects and 3.3&#37: reduction in maximum cooling load in Kuwait, respectively.

Analytical Model for Investigating Linear and Non-linear Behaviour of Thin Semi-conductive Layers on Insulator Surface

Analytical Model for Investigating Linear and Non-linear Behaviour of Thin Semi-conductive Layers on Insulator Surface

Application of Hyperspectral Image Recognition Technology in Monitoring the Pollution Level of Insulators

Abstract The pivotal aspect of ensuring the secure and stable functioning of Electrical Power Systems (EPS) lies in the online monitoring of transmission line insulator pollution levels, aimed at forestalling pollution flashover incidents. These flashovers typically stem from the buildup of contaminants on insulator surfaces, which, under humid conditions, establish a conductive layer, gravely jeopardizing grid security. Traditional pollution detection approaches, inclusive of manual inspections and offline sampling analyses, suffer from drawbacks like inefficiency, inadequate real-time capabilities, and vulnerability to human intervention, thereby struggling to align with the demands of contemporary power grid intelligence and automation. In view of this, this article innovatively proposes an insulator pollution monitoring model based on hyperspectral image recognition technology. This model fully utilizes the unique spectral integration feature of hyperspectral images, which can provide rich spectral data while obtaining image information, covering a wide spectral range from visible light to infrared and even more, and has extremely high spectral resolution. The experimental results show that the model not only significantly improves the accuracy and real-time performance of pollution detection, but also overcomes many shortcomings of traditional methods.

Surface charge-induced electrospray for high-throughput analysis of complex samples and electrochemical reaction intermediates using mass spectrometry.

Electrospray-related ion sources are promising for direct mass spectrometric analysis of complex samples, but current protocols suffer from complicated components and low analytical sensitivity. Here, we propose a surface charge-induced electrospray ionization (SCIESI) inspired by flashover on an insulator surface under high voltage. This protocol not only effectively avoids contact between the sample solution and metal electrode, but also allows completion of the entire analytical process in less than 40 seconds and limits of detection in the pictogram per milliliter range. SCIESI coupled to mass spectrometry can also be used to monitor electro-chemical processes, and a number of oxidation and reduction reactions have been studied, demonstrating that it is a powerful tool for understanding electrochemical reaction mechanisms.

Influence of intense vertical component electric field with the direction away from insulation surface on streamer discharge

Influence of intense vertical component electric field with the direction away from insulation surface on streamer discharge

Surface charge density and induced currents by self-charging sliding drops.

Spontaneous charge separation in drops sliding over a hydrophobized insulator surface is a well-known phenomenon and lots of efforts have been made to utilize this effect for energy harvesting. For maximizing the efficiency of such devices, a comprehensive understanding of the dewetted surface charge would be required to quantitatively predict the electric current signals, in particular for drop sequences. Here, we use a method based on mirror charge detection to locally measure the surface charge density after drops move over a hydrophobic surface. For this purpose, we position a metal electrode beneath the hydrophobic substrate to measure the capacitive current induced by the moving drop. Furthermore, we investigate drop-induced charging on different dielectric surfaces together with the surface neutralization processes. The surface neutralizes over a characteristic time, which is influenced by the substrate and the surrounding environment. We present an analytical model that describes the slide electrification using measurable parameters such as the surface charge density and its neutralization time. Understanding the model parameters and refining them will enable a targeted optimization of the efficiency in solid-liquid charge separation.

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.

Partial discharge characteristics of epoxy insulation surface under AC/LI superimposed voltages in SF6/N2 gas mixtures

Partial discharge characteristics of epoxy insulation surface under AC/LI superimposed voltages in SF₆/N₂ gas mixtures

Highlighting capacitive phenomena in the discharges propagation on the insulators surface immersed in fluids

Highlighting capacitive phenomena in the discharges propagation on the insulators surface immersed in fluids

Enhancing Surface Insulation Performance of Ceramic for Spark Plug by APPJ Treatment

Enhancing Surface Insulation Performance of Ceramic for Spark Plug by APPJ Treatment

Інформаційна технологія оцінювання теплоізоляції багатошарових стін

In today's conditions, the problem of insulation of surfaces is very relevant for wide circles of the population of Ukraine. Everyone knows that surface insulation allows to reduce heat transfer due to the use of materials with low thermal conductivity. In the absence of permanent heating, the issue of thermal insulation of cylindrical pipes is very relevant. The issue of insulation selection and structural design requires a complex and professional approach. To calculate the problem of thermal insulation, a specialist needs to have a toolkit for calculating the temperature field and saving the obtained results for further analysis. The work presents the developed information technology that allows a specialist to calculate the temperature field for multilayer cylindrical pipes. The object-oriented programming language C# and the Microsoft Visual Studio integrated development environment were used to build the IT toolkit. It should be noted that when making calculations, there is no need to specify the characteristics of pipe and insulation materials, since all data is stored in the IT database. The object-relational database management system - PostgreSQL was used to build the data module. After the calculations, all the built calculation models and the received numerical models of the results are also stored in the database. This allows you not to recalculate if necessary, but to use the data that is already available. To analyze the results, the developed toolkit allows you to plot temperature changes of a multilayer wall. At the same time, the user selects the necessary calculation models independently from IT database data. The DirectX three-dimensional graphics development tool package is used for visual representation of numerical model calculations. The authors developed an algorithm for constructing a color temperature field according to the calculations. Red is chosen for the highest field temperature, and blue for the lowest temperature. A feature of the proposed information technology is that its functionality allows three users with different levels of access to work with the toolkit: a database administrator, a mathematical model construction engineer, and a numerical model analysis specialist.

Simulation of transient heat transfer in multilayer walls with photovoltaic cell and air by using efficient numerical methods

This paper focuses on simulating nonlinear transient heat transfer in multilayer walls under varying heat loads, using efficient numerical algorithms. The algorithms employed are completely explicit and unconditionally stable for the linear conduction-convection case. The study investigates heat transfer through building walls, considering different wall geometries and heat load scenarios, encompassing both cooling and heating. Our primary objective is to analyse how heat transfer depends on the wall materials and evaluate algorithm performance in cases involving heat transfer between solid surfaces and fluid (convection) on the outdoor surface, particularly across an air gap between insulation and Photovoltaic Cells (PVC). The results reveal that insulation prevents heat from entering the building, maintaining a comfortable indoor environment. Forced convection significantly enhances heat dissipation, especially during cooling operations to protect PVC with limited working temperature. Furthermore, the simulations highlight the air gap's efficiency in cooling PVC and reducing maximum temperatures on the insulation's outer surface, especially under forced convection conditions. The test results show that the leapfrog hopscotch algorithm offers the best solution for this highly stiff system, followed by the asymmetric and shifted hopscotch algorithms. This study offers insights into optimizing heat transfer within multilayer walls, with implications for building energy efficiency and thermal comfort.

The Effect of Conductivity on Surface Leakage Currents on Iced-Covered Insulators

Insulators on power transmission systems today are vital to ensuring the reliable and effective operation of high-voltage lines. However, it is inevitable that insulators will encounter problems such as contamination and icing due to natural environmental conditions and environmental factors. Pollution layers and ice buildup that have developed on insulator surfaces have a detrimental impact on insulation performance, increase surface leakage currents, and result in power line failures or interruptions. This article focuses on understanding the phenomena of contamination and icing in insulators, evaluating their effects, and investigating methods that can be taken to prevent or reduce these problems. For this purpose, solutions with different conductivity values were sprayed on the insulators in the laboratory environment, and ice covering the insulator surface was provided. Leakage currents were investigated by applying an alternating voltage with mains frequency to the insulators. Data were obtained with the help of the LabVIEW program, and the relationship of leakage currents of porcelain, glass, and silicone insulators with conductivity was compared.

Heterogeneous Electron Transfer with Redox Active Insulating Solid

For more than a century, electron transfer kinetics at electrode/electrolyte interface has been studied for dissolved redox active species at conductors (heterogeneous) or amongst dissolved redox species (homogeneous). However, a third major case is almost unexplored: dissolved redox species exchanging charge with redox active insulators. The electron transfer with redox active insulators such as Lithium peroxide (Li2O2), Lithium sulfide (Li2S), Sulfur (S8), Lithium carbonate (Li2CO3) are salient feature and central difficulty of next generation ‘beyond intercalation’ batteries such as metal-air (O2), metal-CO2 and metal-sulfur (Li-S) batteries.Redox mediation is the key process in electrochemistry with insulators. Mediators shuttle charge between the electron-conducting electrode and the surface of the insulating storage material to drive the discharge or charge reaction by reducing or oxidizing the surface of the redox active insulator. Mediation is now widely accepted to be key to high efficiency, rate capability, and lifetime. It may on the one hand involve external mediators that are added as an electrolyte additive and which have been studied in a wide variety for metal-O2 cells and a few examples for metal-sulfur. On the other hand, there is inherent mediation, where soluble intermediates act as mediators, such as lithium polysulfides in lithium-sulfur batteries. However, surprisingly little attention has been devoted to quantitatively assessing heterogeneous reaction kinetics between mediator and storage material. Work so far clearly shows that the kinetics of this electron transfer step is overall rate limiting and decisive to understand and to control reaction mechanisms towards improving energy efficiency, rate capability, capacity, and cycle life, which underscores the urgency to measure them and to identify governing factors.Here we systematically assess heterogeneous electron transfer at redox active insulators and identify governing factors. Particular systems we present to investigate are twofold. First, mediated kinetics of (su)peroxide oxidation. Our previous work has strikingly discovered decreasing electron transfer rate as the driving force (mediator redox potential) increases beyond a certain value, which represents a first example of Marcus inverted-region behaviour for heterogeneous reactions1. We are leveraging the predictive value of this finding regarding possibilities to impact maximum kinetics and the occurrence of a separate kinetic parabola for singlet oxygen evolution. Second, mediated kinetics of S8 reduction and Li2S oxidation2. Major tools to assess kinetics include following species concentration over time using UV-Vis-NIR spectroscopy and Scanning Electrochemical Microscope (SECM). Doing so requires deconvoluting spectra of mixtures of mediator oxidation/reduction states even if pure substance spectra cannot be obtained. Particularly, obtaining kinetics in S chemistry requires assessing dynamic equilibria of multiple species, for which we develop chemo-metrics tools. The results afford detailed insights into kinetics, thermodynamics, and reaction mechanisms, allowing them to influence in an informed way.References K. Petit, E. Mourad, C. Prehal, C. Leypold, A. Windischbacher, D. Mijailovic, C. Slugovc, S. M Borisov, E. Zojer, S. Brutti, O. Fontaine, S. A. Freunberger, Nature chemistry, 13, (2021)465–471 (https://doi.org/10.1038/s41557-021-00643-z)Cao, X. Shen, A. Wang, F. Yu, Y. Wu, S. Shi, S. A. Freunberger, Y. Chen, Nature Catalysis, 5, (2022) 193–201 (https://doi.org/10.1038/s41929-022-00752-z)

Fundamental Study of Spacer‐Insulation‐Performance Improvement by Nonlinear‐Resistance Material

Coating the surface of insulators used in a gas‐insulated switchgear (GIS) with nonlinear‐resistance material is expected to increase breakdown voltage by reducing the electric‐field concentration when metal particles adhere to the insulators. In this study, an epoxy resin with zinc oxide was used as a nonlinear‐resistance material. Tensile strength, adhesion by heat cycle test, hardness, and resistance to decomposition products of sulfur hexafluoride gas were evaluated for the nonlinear‐resistance material. It was confirmed that there were no problems with mechanical properties for application to GIS. The nonlinear‐resistance material was spray‐coated on actual post spacers, and the breakdown voltage was evaluated when metallic particles adhered to the post spacers. When the coating thickness was 20–35 μm, the breakdown voltage increased by about 8%. When the coating thickness was 50– 68 μm, however, the breakdown voltage increased by 23%, confirming that the breakdown voltage of an actual spacer improved. © 2023 Institute of Electrical Engineer of Japan and Wiley Periodicals LLC.

Bound States of a Short-Range Defect on the Surface of an Intrinsic Antiferromagnetic Topological Insulator in a Noncollinear Phase

The features of electronic states on the surface of an intrinsic antiferromagnetic topological insulator (AFM TI) containing defects are theoretically investigated. Our approach takes into account the role of the electrostatic potential and the variation in the orientation of magnetic moments in the near-surface layers. A change in the spectral characteristics of the surface states under the transformation of magnetization from an equilibrium AFM phase of A-type to a ferromagnetic phase through a noncollinear texture is described. It is shown that in AFM TI with uniaxial anisotropy, an external magnetic field applied along the easy axis can cause a significant modulation of the exchange gap size in the spectrum of surface states and even invert the gap sign. Modeling the single defect effect as a surface potential perturbation over a finite scale, we analytically investigate the formation of a bound state and its behavior depending on the strength of potential and exchange scattering by the defect and the exchange gap size. The energy level of the bound state is demonstrated to experience a sharp shift in the vicinity of the spin-flop transition. The theoretical results obtained allow us to provide a consistent explanation of recent experimental data on scanning tunneling spectroscopy of antisite defects on the surface of the prototype AFM TI MnBi2Te4 in an external magnetic field.

Acoustics and the well-being of children and personnel in early childhood education and care

Studies implementing a multimethod perspective in evaluating the acoustics of early childhood education and care (ECEC) spaces both quantitatively and qualitatively are still scarce. In this study the acoustic environments (noise levels and reverberation times) of seven Finnish ECEC group’s premises were examined in association with personnel’s (N = 22) and children’s (N = 71) well-being. Personnel’s well-being and vocal health and children’s well-being were assessed with questionnaires. The findings were further elaborated by documentation of the ECEC spaces and semi-structured interviews with the ECEC personnel detailing their views on the acoustic environment of the daycare buildings and how and if the acoustics should be improved. The results showed that noise exceeding 70 dB affected personnel’s vocal health negatively, whereas no associations were found regarding acoustics and children’s or personnel’s well-being. Based on the interviews, sound spreading, poor insulation, and hard surfaces add to negative experiences of noisiness. ECEC groups need spaces that can be closed and acoustically separated from each other and from other groups. The possibility to close a space supports the perceived well-being of the users and provides a more varied and individualized use of the spaces.