Types Of Insulators Research Articles

Applied Insulating Coatings for Gas Distribution Pipelines in the Republic of Belarus and Their Characteristics

Gas distribution system is a production complex, which is part of the gas supply system and consists of organizational and economically interconnected facilities designed to organize the supply of gas directly to consumers. On the national basis of the gas distribution system is formed by about 67.0 thousand km of external distribution gas pipelines, 28.0 thousand km of which are underground steel pipelines. As potentially hazardous objects, steel underground distribution pipelines are subject to higher requirements for corrosion protection. As a rule, they are provided with complex anticorrosion protection, an obligatory component of which is insulation coatings. Taking into account the above mentioned, the definition of general indicators characterizing condition of insulation, the degree of its wear is an actual task. To solve it, for the first time, we have analyzed an array of long-term statistical data on defects of protective coatings of distribution gas pipelines, detected by instrumental method. The values of specific defect density Dd and damageability Ad have been determined for all types of applied protective coatings. The best values have been found for insulation on the basis of heat-shrinkable tapes. The characteristic damage of the protective coating on the basis of bituminous mastics (microcracks), which can be used as an indicator of aging of this type of insulation, has been determined. It has been shown that defect formation in the insulation coatings of gas pipelines up to the present time is, as a rule, a low-intensive process, which has been confirmed, among other things, for gas pipelines operated for a long time. The obtained results were included into the justification of abolition of the previously used 40-year normative service life of steel gas pipelines in the new edition of the Rules of Technical Safety in the Field of Gas Supply of the Republic of Belarus.

Analysis of Natural Pollution Accumulation Characteristics of Insulators for Railroads in High-Altitude Environment

Railway system insulators are affected by pollution, altitude, and other environmental situations during operation, which causes reduced electrical performance or even flashover accidents. These factors threaten the safety of railway operations in high-altitude areas. However, the natural contamination characteristics of a railroad in a plateau area is still unclear. In this study, a natural pollution accumulation test for railway insulators in a high-altitude area was carried out, and the distribution rules of nonsoluble deposit density (NSDD), equivalent salt deposit density (ESDD), NSDD/ESDD ratio, and nonuniformity (T/B) of the pollution distribution of the tested insulators were calculated. Meanwhile, the chemical compositions of the pollution from different test sites were analyzed. The differences of pollution accumulation between railway insulators and suspended insulators of a power system and the influencing factors were compared and analyzed by combining with a numerical simulation. The results show that the pollution level of railroad insulators is mainly distributed in level b and above. A pollution sample is mainly composed of sodium chloride, while the NSDD/ESDD ratio of pollution is mostly distributed from 0 to 5, with T/B value ranges from 1/0.62 to 1/1.76. The amount of insulator contamination is influenced by the location inside and outside the tunnel. Additionally, the pollution amount is influenced by the structure and type of insulators. Finally, this paper studies the creepage distance and structural height required by railway insulators in a plateau area according to the natural pollution accumulation characteristics of railway insulators, which can provide a reference for a railway electrical external insulation configuration in a high-altitude area.

Modelling and analysis of electrical performance outdoor glass insulator under various services and lightning impulse

This paper is focus on modelling of glass type insulator with voltage rating of 275 kV. The glass insulators are still widely served in overhead transmission line because of its high dielectric strength capability. However, their outdoor application has resulted in the exposure to the various service conditions such as weather, pollution and lightning conditions. Further, the inclination effect of the insulator under the nominal voltage and lightning impulse is modelling through Finite Elementary Method (FEM). Then, the model of glass insulator is constructed in three different inclination angles by using the Ansys Maxwell 3D for simulation purpose. The results show the inclined insulator due to the wind load effect has the lowest breakdown voltage at most 53.33% compared with the vertical insulator. Under the outdoor environment factors such as humid, wet and contamination, the localized electric field and current density had increased significantly. Consequently, this situation may cause the power losses, localized heating effect also reduces the electrical performance of the insulators.

Thermal Evaluation of Silica-Based Insulated Magnet Wires from the Sol-Gel Process.

The conventional enameling process used in the fabrication of magnet wires requires harmful processes and products. The target of the industry in the actual context of electrification is to increase the electrical machines' efficiency. Indeed, the electrical insulation systems (EIS) of an electrical machine undergo various environmental constraints that can shorten their lifespans. Consequently, aspects of the insulation need to be improved, such as its thermal resistance. One of the challenges is to implement sustainable technology without losing performance. This work consists of the thermal performance evaluation of new magnet wires insulated by three types of composites of silica-based solution from the Sol-gel process and amorphous polyamide-imide (PAI). These composite coats are overcoated by an extruded thermoplastic resin with and without fillers. Different types of insulation are tested and compared to determine the better configuration. Thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR) analysis, scanning electron microscopy (SEM) analysis, curing characteristics by tangent delta curve, and thermal-aging tests at three temperatures were carried out on the different EIS systems. Dielectric measurements were made between thermal-aging cycles. Their basic mechanical, electrical, and thermal characteristics are promising: the cut-through temperature is situated above 430 °C, their breakdown voltage values are between 5 kV and 9 kV (grade 3), and a good adhesion (overcoming more than 140 turns on a peel test). The thermal-aging results have been consistent with the TGA analysis results. The thermal index following the IEC standards was estimated for the selected EIS, which would have the main basic characteristics of a magnet wire of 200 class; moreover, it would be a greener enameled wire compared to the conventional one.

Breakdown strength analysis of XLPE insulation types: A comparative study for multi-layer structure and voltage rise rate

Multi-layered structures are commonly used in high voltage applications to improve the electrical, mechanical, and thermal stability of insulation systems. This study investigates the breakdown strength of two commonly used cross-linked polyethylene (XLPE) types by conducting detailed experiments considering the effects of multi-layered structures, material thicknesses, and voltage rise rates. Although there are existing studies on the impact of thickness and voltage rise rate, there is a paucity of research specifically focusing on these factors within the framework of multi-layered structures. Experimental results showed that the breakdown strength of both samples exhibited greater values at the higher voltage rise rate. When the breakdown strengths were examined according to the layer structure, it was seen that the multi-layer insulation structures had higher breakdown strengths. Specifically, the maximum increases were 17.96% and 23.80% for peroxide-added and silane-added XLPE samples, respectively. Moreover, it was revealed that silane-crosslinked samples had higher breakdown strengths in all cases. Finally, the structures of the test samples were examined by scanning-electron microscope (SEM) analysis and the impacts of the findings were evaluated through the simulations in COMSOL Multiphysics®. Simulation results showed that rough and inhomogeneous material structure dramatically increased the electric field intensity acting on the multi-layer insulations.

Impact of air pressure variations on electrical vehicle motor insulation

AbstractVariation in air pressure severely affects the insulation of electric vehicle (EV) motors, hence weakening the reliability of EVs for safe operation. Nomex‐polyimide‐Nomex, a typical insulation material for EV motors, was used to investigate the motor insulation performance under different air pressures. The results show that the partial discharge inception voltage is significantly reduced for EV motors operated at lower air pressures, and the probability of partial discharge (PD) occurrence is increased. The macroscopic results reveal that the active area of the PD expands at low pressure, while the non‐corroded ring appears in the centre. Additionally, although the number and amplitude of the PD increase significantly with decrease in air pressure, the active area of the PD expands and electrical stress on the insulation per unit area increases slowly. Therefore, when the pressure decreased from 60 to 40 kPa, the endurance life does not show a significant downward trend. Furthermore, the dielectric constant and loss of the low‐pressure samples significantly change during the ageing process, which further indicates critical degradation of the insulation. The aforementioned investigations reveal that the air pressure at different altitudes has a significant impact on the performance of insulation materials.

Forensic Analysis of Roof Deterioration Due to Condensation

Corrosion of the structural steel roof deck of large warehouses resulted in several invasive forensic investigations to determine the cause and mechanism of the corrosion. The warehouse roof investigation presented in this paper is one of many similar warehouses located near the Gulf of Mexico and along the Southern Atlantic Seaboard experiencing corroded roof decks when constructed using fiberboard roof insulation made from sugarcane fiber called bagasse. Consensus exists among individuals studying this phenomenon that the fiberboard became saturated with water, which dissolved formic and acetic acid from the fiberboard. The steel deck corroded when it came in contact with the acidic solution. There was little consensus regarding the mechanism by which water intruded into the roof assembly. Invasive investigation of the low-slope roofs of buildings with various types of insulation (including bagasse fiberboard) and observation of physical commonalities between the instances led to the following conclusion: Water in the roof assemblies did not result from leaks through a compromised roof membrane but rather from humid air infiltrating the roof assembly and condensing on the underside of the roof membrane.

Study of changes in leakage currents under a contaminated and moistened surface of insulators of the PS-6B, PS-120A, PSD-70E types of overhead power lines

In the process of operation, insulators are exposed to repeated pollution and atmospheric influences. This is due to the removal of pollutants from industrial metallurgical enterprises, chemical plants and their deposition on the surface of insulators near power transmission lines. In normal operation, when the insulators are dirty, but their surface is not wetted, the active component of the total leakage current can be neglected. It is another matter when the surface of the contaminated insulator is intensively moistened by atmospheric influences, for example: rain, fog, dew, respectively, and the value of the active component of the leakage current also increases in proportion to the conductivity of the formed electrolyte, the layer of contamination on the surface of the insulating surface of the insulator. The article discusses the method of measuring leakage currents on the contaminated surface of various types of glass plate insulators in laboratory conditions, with artificial and natural contamination. In the dry state, a leakage current flows through contaminated insulators, which mainly depends on the electrical capacity of the insulator. A method of calculating the active component of the leakage current is proposed, since the active component of the leakage current is the main parameter for determining energy losses due to its dissipation into the environment. The results of the change in the value of the leakage currents in the time characteristics after wetting the surface layer of pollution to the leakage current in the dry state of the insulator surface are given. The observation of drying processes of a contaminated and moistened surface due to the influence of leakage currents is given. The formation of dried zones on the surface of contaminated insulation of plate insulators of overhead power lines under the action of leakage currents was investigated. An analysis of the obtained results was carried out, conclusions were drawn.

Coexistence of Magnon-Induced and Rashba-Induced Unidirectional Magnetoresistance in Antiferromagnets.

Unidirectional magnetoresistance (UMR) has been intensively studied in ferromagnetic systems, which is mainly induced by spin-dependent and spin-flip electron scattering. Yet, UMR in antiferromagnetic (AFM) systems has not been fully understood to date. In this work, we reported UMR in a YFeO3/Pt heterostructure where YFeO3 is a typical AFM insulator. Magnetic-field dependence and temperature dependence of transport measurements indicate that magnon dynamics and interfacial Rashba splitting are two individual origins for AFM UMR, which is consistent with the UMR theory in ferromagnetic systems. We further established a comprehensive theoretical model that incorporates micromagnetic simulation, density functional theory calculation, and the tight-binding model, which explain the observed AFM UMR phenomenon well. Our work sheds light on the intrinsic transport property of the AFM system and may facilitate the development of AFM spintronic devices.

Numerical investigation of suppressing thermal runaway propagation in a lithium-ion battery pack using thermal insulators

Thermal runaway propagation (TRP) in a lithium-ion battery pack is crucial to its safety concerning the potential hazards of fire or explosion. In current study, a TRP suppression method for a 4 × 4 battery pack using three insulation materials, silicate, ceramic and glass fiber boards, is numerically investigated. Reliability of the model is first verified by experimental temperature of a single battery during TR. Then, three sets of TRP scenarios initiated by external heating are studied to reveal the effects of insulation type, thickness (0.5–4 mm) and layout. The results show that thermal conductivity of insulation impacts its performance more greatly than thickness, and glass fiber outperforms silicate and ceramic fibers in preventing TRP. Bidirectional layout (BL) of insulation boards performs better than unidirectional layout (UL). For UL, row-to-row TRP exists and the TRP process is accelerated compared with non-insulation case if insulation boards fail, implying UL can prevent TRP only if the row-to-row TRP is inhibited. While for BL, TRP is only observed for 0.5 mm silicate fiber boards, and the critical heating power (6.5 kWm−2) triggering TRP in battery pack is much lower. The outcomes may provide useful theoretical bases and suggestions for safety design and risk assessment of battery pack.

Active Control Strategy of Partial Discharge for Insulation of High-Power High-Voltage High-Frequency Transformers (H3Ts)

The insulation coordination design against electric-originated complex operation conditions is one of the critical challenges for high-power, high-voltage, high-frequency transformers (H <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> T) in solid-state transformers (SSTs). The connection between the insulation performance and the operational parameters of H <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> T are tightly coupled, but their interaction has been ignored till now. In this letter, an active control method is proposed by adjusting the voltage amplitude, frequency, and temperature to decrease partial discharge (PD) to improve the high reliability of H <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> T. At first, PD versus voltage level, frequency, and temperature in existing typical insulation are identified. Then, the PD rules of different parameters are utilized to provide feedback information and guideline for the control of H <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> T. This letter aims to improve the reliability of H <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> T through active control of PD activities.

Quantifying Multi-Scale Performance of Geometric Features for Efficient Extraction of Insulators from Point Clouds

Insulator extraction from images or 3D point clouds is an important part of automatic power inspection by unmanned airborne vehicles (UAVs), which is vital for improving the efficiency of inspection and the stability of power grids. However, for point cloud data, many challenges, such as the diversity of pylon shape and insulator type, complex topology, and similarity of structures, were not tackled with the study of power element extraction. To efficiently identify the small insulators from complex power transmission corridor (PTC) scenarios, this paper proposes a robust extraction method by fusing multi-scale neighborhood and multi-feature entropy weighting. The pylon head is segmented according to the aspect ratio of horizontal slices following the locating of the pylons based on the height difference and continuous vertical distribution firstly. Aiming to quantify the different contributions of features in decision-making and better segment insulators, a feature evaluation system combined with information entropy, eigen entropy-based optimal neighborhood selection, and designed multi-scale features is constructed to identify suspension insulators and tension insulators. In the optimization step, a region erosion and growing method is proposed to segment complete insulator strings by enlarging the perspectives to obtain more object representations. The extraction results of 82 pylons with 654 insulators demonstrate that the proposed method is suitable for different pylon shapes and sizes. The identification accuracy of the whole line achieves 98.23% and the average F1 score is 90.98%. The proposed method can provide technical support for automatic UAV inspection and pylon reconstruction.

Determination of individual values of four-element equivalent circuits elements parameters at technical diagnostics of insulation by absorption methods

The aim of this article is to present a methodology of determining of the individual values of the parameters of four-element equivalent circuits for insulation with through conductivity. Methodology. The proposed method consists in the fact that at a time interval of more than 10 s, when the charge indicator no longer contributes to the leakage current, three points t1, t2 and t3 are selected, such that t2 – t1 = t3 – t2. To be able to determine the absorption coefficient R60/R15, it is recommended to take t1 = 15 s, t2 = 37.5 s and t3 = 60 s. At the same time, by subtracting I(t2) – I(t1) and I(t3) – I(t2), the constant component of the absorption curve is excluded and it becomes possible to determine the individual values of the parameters of the generalized equivalent circuit of insulation, additionally using its conductivity in operator form. Results. As calculations show, the correct determination of the parameters of insulation equivalent circuit according to the proposed method is possible only with a certain ratio of these parameters. The charge time of the geometric capacitance Cg(R0+Rd), where R0 and Rd are the resistance that forms the charging exponent, and the resistance of the sensor, should be within 0.2 s &lt;Cg(R0+Rd)&lt;1 s, the time constant CaRa, where Ca and Ra are the capacitance and resistance of the absorption chain, should be more than 3 s, the product of CgRl, where Rl is the leakage resistance, more 0.5 s, the leakage resistance Rl is less than the absorption resistance Ra. Checking the methodology on a model example gives the values of the parameters of the insulation equivalent circuit that match the specified ones with high accuracy. Practical value. The use of individual values of the parameters of insulation equivalent circuits when applying absorption diagnostic methods with considering the time values and dimensional factors, allow to calculate all currently used diagnostic parameters, to determine the conditions of certain insulation types, as well as in more detail, in comparison with the existing approach, to assess the technical condition of the insulation and the reasons of its changes.

A Comparative Study of Abnormal Heating Composite Insulators.

The abnormal heating of composite insulators on transmission lines frequently occurs, seriously threatening the power grid's safe and stable operation. For different types of abnormal heating composite insulators, undifferentiated replacement wastes a lot of labor and material resources. This study explores the abnormal heating composite insulators under different environmental humidity and wind speed conditions. The heating and discharge of composite insulators are observed, and the heating range, heating shape, and temperature rise (ΔT) are analyzed. The abnormal heating of the sheath-aging composite insulator is related to the aging of the silicone rubber and the environmental humidity. The partial discharge caused by the core rod's defect is the primary source of the temperature rise in the decay-like insulator. The heating range of the contaminated insulator is connected to the environmental humidity, and the ΔT increases with the salt density. The ΔT and heating range of the three types of abnormal heating increase with the ambient humidity. The heating phenomenon under low humidity is an important characteristic that distinguishes decay-like and contaminated insulators from sheath-aging insulators. Therefore, the on-site infrared inspection should be carried out in sunny and windless weather to prevent the impact of high humidity and wind speed on infrared temperature measurement.

Transient analysis and optimization of an off-grid hydrogen and electric vehicle charging station with temporary residences

In this research study, an off-grid zero energy refueling station for hydrogen fuel cell vehicles with the ability to charge battery-powered electric vehicles is designed and analyzed transiently. A temporary residence next to the charging station is designed to accommodate people who come to the charging station. The best energy supplier in terms of cost is determined. The insulation thickness of the temporary residence wall is optimized for five types of insulation and thickness between 0 to 0.7 m. Total cost over 20 years (system lifetime) is an objective function that should be minimized. Using Trnsys software, the charging station and temporary residence are simulated. The system's total costs for different insulation type and thickness is predicted using a machine-learning approach. The optimum insulation type and thickness are determined. According to the results, choosing a photovoltaic panel as a power source is up to 33,024 $ more cost-effective than wind energy for the mentioned system. The optimal insulation thickness is related to expanded polystyrene with a thickness of 0.24 m. Insulation thickness and type can affect the system's total cost intensively. The cheapest insulation is not the best in reducing total cost.

Assessing the environmental impact of using CLT-hybrid walls as a sustainable alternative in high-rise residential buildings

Cross-laminated timber (CLT), a bio-based material, is attracting attention as an alternative to conventional materials, to reduce the environmental impact of the construction sector. To the expansion of CLT application, the environmental impact of applying CLT, which was mainly used in low- and middle-rise buildings, to the outer walls of high-rise residential building was analyzed. The environmental impacts of 28 alternative walls were analyzed based on variations in CLT thickness and insulation type. Replacing traditional walls with CLT, including finishes, alternatives resulted in an average reduction of −35% in environmental impact. According to the standardized and weighted process, cellulose and glass wool are the most environmentally friendly alternatives.

Energy performance gap of the Italian residential building stock: Parametric energy simulations for theoretical deviation assessment from standard conditions

Energy Performance Gap (EPG) is a crucial issue in the building sector that can lead to an overestimation of the national energy policies. It is the difference between the calculated energy consumption and actual energy use, and it is relevant mainly for space heating. As EPG quantification or correction methods could lead to more realistic energy policies, EPG has become a focus of many studies and research. In this framework, this study aims to quantify the theoretical deviation of EPG, i.e., concerning to the standard conditions, for the Italian residential building stock by performing parametric energy simulations of thousands of representative reference buildings. After a comprehensive thermophysical characterization of the national building stock, parametric simulations were carried out by varying the main standard conditions set in the Energy Performance Certificate (EPC) calculation. This approach allowed the quantification of EPG according to the climatic zone, building type, usage profile, and thermal insulation level of buildings, while also analysing the influence of these parameters on the EPG and checking for prebound or rebound effects (i.e. when standard consumption is greater or smaller than actual one). The study identified a range of EPG variability for both prebound (0% to +80%) and rebound (−30% to 0%) effects and quantified an average EPG between −3 and +16 kWh per heating degree day of the selected location as a function of the usage profile. This work represents the first attempt to calculate the EPG of the Italian residential building stock and it could lead to the correction of the national energy policies implemented in the building sector.

Room‐Temperature Charge‐to‐Spin Conversion from Quasi‐2D Electron Gas at SrTiO3‐Based Interfaces

Interfacial two-dimensional electron gas (2DEG), especially the SrTiO3-based ones at the unexpected interface of insulators, have emerged to be a promising candidate for efficient charge-spin current interconversion. In this article, to gain insight into the mechanism of the charge-spin current interconversion at the oxide-based 2DEG, we focused on conducting interfaces between insulating SrTiO3 and two types of aluminium-based amorphous insulators, namely SrTiO3/AlN and SrTiO3/Al2O3, and estimated their charge-spin conversion efficiency, {\theta}_cs. The two types of amorphous insulators were selected to explicitly probe the overlooked contribution of oxygen vacancy to the {\theta}_cs. We proposed a mechanism to explain results of spin-torque ferromagnetic resonance (ST-FMR) measurements and developed an analysis protocol to reliably estimate the {\theta}_cs of the oxide based 2DEG. The resultant {\theta}_cs/t, where t is the thickness of the 2DEG, were estimated to be 0.244 nm-1 and 0.101 nm-1 for the SrTiO3/AlN and SrTiO3/Al2O3, respectively, and they are strikingly comparable to their crystalline counterparts. Furthermore, we also observe a large direct current modulation of resonance linewidth in SrTiO3/AlN samples, confirming its high {\theta}_cs and attesting an oxygen-vacancy-enabled charge-spin conversion. Our findings emphasize the defects' contribution to the charge-spin interconversion, especially in the oxide-based low dimensional systems, and provide a way to create and enhance charge-spin interconversion via defect engineering.

Defects Detection of Onboard Cable Termination in EMUs Using Partial Discharge Measurement and SDP-DL Framework

Termination is the most important part of on-board cable, which plays a vital role in ensuring the continuous and reliable power supply to EMUs (electrical multiple units). The maintenance time of EMUs is limited, so the time left for PD (partial discharge) measurement of on-board cable termination is very short, leading to the obvious decreasing of detection accuracy. For addressing this issue, this paper proposed an SDP (symmetrized dot pattern)–DL (deep learning) framework to detect the insulation defects using time series PD pulse signal. First, a PD measurement platform and experimental samples were prepared in laboratory to obtain the time series PD pulse signals of four typical insulation defects. Then, the time series PD signals were converted into SDP images using the proposed parameter optimization method. Finally, the SDP-DL framework was proposed, and three specific and typical methods were utilized, i.e., CNN (convolutional neural network), SAE (stacked auto encoder) and DBN (deep belief network). The results show that the performance of SDP-DBN method is the best, and the insulation defects can be detected with accuracy of 96.1%. In addition, the visualization ability of data increases after SDP transformation of the original PD time series signal.

Thermal stability investigations of different aerogel insulation materials at elevated temperature

Super thermal insulation materials with low thermal conductivities, such as aerogels and vacuum insulation panels, are increasingly pushing conventional thermal insulations out of the market. Super insulation materials such as aerogels can be used easily on both vehicles and buildings. Nowadays, their usage by pipes transporting hot medium is also widespread. In these environments where elevated temperatures (100–250 °C) are applied, it is a basic requirement that they should keep their excellent thermal insulating capability. In this study, a comprehensive examination performed on two new silica-aerogel type insulations is presented. We investigated the change in the thermal performance of different types of aerogel insulations (Slentex and Pyrogel) after thermal annealing, ageing them at 150 and 250 °C temperatures for 1 day. After these thermal treatments, their thermal parameters such as thermal conductivities and specific heat capacities were measured. We revealed that both the thermal conductivity and the specific heat capacity for the Pyrogel changed considerably after annealing, while for Slentex the thermal conductivity remained constant and the specific heat capacity changed. To understand these changes we executed calorimetry tests and microscopic inspections with different methods. These experiments were completed with X-ray diffractometry to analyze the possible structural changes in the samples. From an application point of view, we consider the importance of these results, since they predict the lifetime of the used insulating material during their industrial use.