Abstract This article presents a research project aimed at developing a method for measuring the intensity of the electric field inducing partial discharges (PDs) in a gaseous defect within a solid insulator. Measurements performed with this method allow observation of PDs only within the defects, thus providing reliable information on the relationship between the temporal and dimensional characteristics of the PDs and the size and geometry of the defect. The advantages of a measurement cell filled with transformer oil compared to a “dry” cell, such as a parallel-plate capacitor, are demonstrated. To solve the problem related to measuring partial discharges in gaseous inclusions in order to determine the technical condition of the solid insulation, the intensity of the electric field in gaseous defects within a solid insulator was calculated using the finite element method with COMSOL Multiphysics 6.2 software. Partial discharge (PD) modeling in MultSim was employed, along with probabilistic and statistical methods for processing the results. The finite element method was used to calculate the electric field non-uniformity coefficient for samples containing gas defects of varying sizes. MultSim modeling allowed us to determine the phase angle between the current and voltage in the cell during partial discharge (PD) measurements. For a cell with a spherical electrode, each containing sectors of a sphere with a radius of R = 25 mm and a largest radius of x = 18 mm in a plane perpendicular to the sector axis, the expected partial discharge parameters were calculated as a function of the insulation defect size. Statistical parameters were determined to reproduce partial discharges (PDs) recorded over a given period and to calculate their duration. During laboratory measurements, a model consisting of eight samples of a paper dielectric of varying thickness: 0.15 mm, 0.2 mm, 0.25 mm, 0.3 mm, 0.35 mm, 0.4 mm, 0.45 mm, and 0.5 mm containing air inclusions simulating a 2 mm diameter defect located near the electrodes was used, but in this article, the results for a model of a single dielectric of thickness of 0.2 mm will be presented. A reference voltage of 12.5 kV was applied to the high-voltage electrode, and partial discharges (PD) were observed in an electric field of intensity 6.747 kV/mm. Based on the experimental results, electric charge diagrams and experimental setups simulating the change in electric fields causing partial discharges are presented. It was experimentally shown that partial discharges in a sample containing a single gas defect occur twice during the period of a sinusoidal voltage at the grid frequency, in the first and third quarters, with the same electric field amplitude inside the gas cavity of the defect.

Polymer materials exposed to electric fields, including those of low to medium intensity, can lead to surface degradation of solid insulators. This property is used as an indicator of material aging. In this experimental study, samples of solid insulators, namely cross-linked polyethylene (XLPE) and polyvinyl chloride (PVC), used in high-voltage cable insulation, were subjected to electrical discharges under ambient conditions and for varying durations of exposure to the electric field generated by two parallel electrodes, one pointed and the other flat. The peak amplitude of the discharge current is proportional to the applied voltage and inversely proportional to the inter-electrode capacitance. The charge associated with the electrical discharge accumulates on the sample surfaces and is proportional to the aging time. Surface condition analysis of the samples was carried out using a scanning electron microscope (SEM). The results revealed significant damage to the surfaces of the samples affected by electrical discharges, including surface erosion observed in the micrographs and a color change on the aged surfaces.

The photoelectric feedback processes leading to growth of relativistic runaway electron avalanches are believed to be responsible for extreme fluxes of γ rays produced from very compact regions of space with dimensions on the order of a hundred meters in association with lightning activity in the Earth's natural environment [V. P. Pasko et al., Photoelectric effect in air explains lightning initiation and terrestrial γ ray flashes, J. Geophys. Res. 130, e2025JD043897 (2025)JGREA20148-022710.1029/2025JD043897]. Here, we demonstrate for the first time that the same photoelectric feedback discharges can be realized on centimeter scales in common solid state dielectric materials, like quartz, acrylic, and bismuth germanate. These discharges can serve as new sources of high energy x-ray radiation.

Abstract Transformers are among the most crucial components of electric distribution and transmission systems, and the grid's stability and dependability are directly impacted by their operation. Polymeric insulation used in transformers and electrical allied areas has recently created an enormous revolution. An epoxy polymer matrix with carbon‐based nano reinforcement is subjected to analyze the possibilities of incorporation as an insulant in dry type transformer. The fabrication process was optimized by varying hardener content and stirring speed using a central composite design integrated with response surface methodology. The developed epoxy/carbon nanocomposites were evaluated for dielectric strength, thermal conductivity, tensile strength, Izod impact resistance, and morphological characteristics to determine their suitability as solid insulation for dry‐type transformer applications. Some algorithm combinations [random forest, neural network, gradient boosting, XGboost gain, and response surface methodology] are examined to determine the most optimal. This study revealed that 6.5% of the sample performed well for all the properties of the study. The optimized sample had a dielectric strength of 140 V/mm, a thermal conductivity of 0.45 W/m K, and an Izod impact of 0.26 (J/mm). RSM was ultimately determined to be a more accurate prediction model than the other algorithms based on the obtained model results. The results indicate that, with an accuracy of 94% for dielectric strength, 98% for tensile strength, 98.4% for Izod impact, and 96% for thermal conductivity, the RSM performs best in forecasting the revolutionizing of the transformer's insulation.

High voltage direct current (HVDC) gas-insulated equipment (GIE) has become a critical component in long-distance power transmission projects, owing to its advantages such as compact structure and high reliability. However, the gas–solid interface insulation of DC GIE under long-term operation faces charge accumulation phenomenon, which will distort the electric field distribution and cause insulation flashover. Due to the lack of technical guidelines for the insulation design of DC gas-insulated equipment, the method of insulation design usually adopts increasing the insulation structure size to ensure sufficient creepage along the surface, which greatly increases the dimensions and manufacturing costs of the final equipment, and fails to fully leverage the unique advantages of GIE in compactness and lightness. Therefore, it is of importance to clarify the mechanism of charge accumulation on the surface of insulators under HVDC, and to propose an insulation design method that can effectively inhibit the charge accumulation and adjust the electric field distribution at the gas–solid interface, which holds practical significance for the safe application of large-scale DC GIE projects. In view of this, this paper firstly summarizes the characteristics of surface charge accumulation at gas–solid interface, and then reviews the existing research progress from two perspectives: surface charge suppression of insulation structure and gas–solid interface electric field regulation, providing theoretical and technical support for optimizing the design of GIE insulation structure, formulating scientific operation and maintenance measures.

ABSTRACT Subsea cable connectors are critical components in offshore power delivery systems. They consist of a plug and receptacle, where current‐carrying parts are enclosed in solid insulation and placed within a liquid‐filled diaphragm. With the growing demand for power transfer and renewable energy integration in subsea environments, there is a need for alternative insulation materials that ensure system integrity while minimising environmental impact. This paper proposes integrating polyether ether ketone (PEEK) with a synthetic ester liquid as the composite insulation system for subsea cable connectors. The study commences with a comparative analysis of the electrical performance of PEEK when immersed in synthetic ester versus mineral oil. The AC breakdown strength (BDS) of PEEK in synthetic ester liquid under varying temperatures and thicknesses is also investigated. Results show that the breakdown strength of PEEK immersed in synthetic ester liquid surpasses that in mineral oil, largely due to the closer permittivity match between PEEK and the ester liquid. Likewise, the BDS decreases with increasing thickness, following a power‐law relationship but remains stable within the tested temperature range of 20°C–80°C. Breakdown locations, estimated using an in‐house MATLAB programme, occurred predominantly near the triple point junction.

Vacuum surface flashover along solid insulator remains a major cause of high voltage device failure, therefore attracts sustainted research interest during the past a few decades. Current investigations of flashover encounter a bottleneck period due to incomplete understanding of the underlying physical mechanism. Optical diagnostics for evolution of surface flashover process can provide a new insight to its mechanism. However, the surface flashover process is a nanosecond (ns) scale transient phenomenon, and most of the existing diagnostic cameras are unable to obtain two-dimensional images with such high temporal resolution. In this paper, a four-framing camera with subnanosecond temporal-resolution is developed and tested. By adopting avalanche transistor switches in the subnanosecond gating module for photocathode in the image intensifier, a minimal gate width of ~1ns of each frame is achieved. A combination of analog and digital circuit is designed to realize a large delay range from picosecond (ps) to millisecond (ms), with a high accuracy of 150 ps within 10 ns range, therefore the time interval between consecutive frames can be adjusted flexibly according to different applications. The developed camera successfully captures the fast-evolving surface discharge processes, providing a powerful diagnostic tool for fundamental flashover mechanism research.

The paper presents the results of investigations having the purpose of selecting parameters derived from partial discharge acquisitions for an accurate identification of defects in solid insulation systems. Partial discharge measurements are performed on Roebel bars with artificial defects, using different test setups and voltage levels. A wide range of parameters derived from partial-discharge height or phase distributions are analyzed to assess their ability to identify defects under different test conditions. To be selected for identification purposes, their values should vary in distinct ranges, each associated with a specific defect. These intervals must remain almost constant, changing the test conditions. If properly organized, parameters related to the shape of phase-resolved partial discharge patterns, the ratio of positive and negative discharge amplitudes, and the shape factor of the two-parameter Weibull function are suitable for identifying different PD sources.

Insulating high voltage electrical equipment involves various aspects such as the advancement of structural designs, the selection of appropriate materials, designing processes, manufacturing techniques, operational protocols, and maintenance procedures. These technologies are crucial for ensuring the safe and efficient operation of electrical appliances that utilize conductors at varying potentials. The insulation structures play a vital role in separating these conductors, thereby emphasizing the significance of backup systems in electrical appliances. Ensuring environmental sustainability in traditional cross-linked polyethylene (XLPE) insulation poses a challenge in meeting the demands of sustainable development. The ultimate phase of the self-repairing mechanism involves the polymerization of monomers, catalyzed by epoxy resin upon contact. This process resembles the electrical breakdown caused by electric trees, often paralleled by mechanical cracking in the material. The effects of these advancements and potential future paths for novel backup systems are deliberated upon in each context. Available from various manufacturers, these systems offer an additional layer of compression through streamlined and integrated technologies. They present an opportunity to enhance the resilience of power plants, particularly in managing surges, as they can be implemented throughout the entire substation, ensuring comprehensive overvoltage control. The voltage applied exhibits variability based on temperature fluctuations. This phenomenon affects conductivity and the accumulation of space charge. The impact of a random electric field generated by this distribution is briefly addressed. Within our expanded VIKOR model, which encompasses various decision criteria, we utilize the Analytic Hierarchy Process (AHP) method to determine weights through fuzzy analysis. The aim of this thesis is to enhance the understanding and application of the Dynamic Intuition is Fuzzy Multi-Attribute VIKOR (DIF-MADM) Method. This involves clarifying the concept and methodology, particularly focusing on integrating the PFNP model and VIKOR method into a cohesive framework. The thesis seeks to develop a fuzzy normalized schema for the VIKOR method, thereby contributing to its expansion and clarity. It will also review the current state of VIKOR applications, classify and analyze existing research, and provide a comprehensive explanation of the topic through a modern literature review. The text implies that the discussion extends to additional aspects of VIKOR. With the introduction of new measures, the text suggests confidently employing the fuzzy VIKOR method. It proposes a method for multi-criteria decision-making that incorporates optional information, expressing assurance in its effectiveness. To demonstrate its utility, a practical example is provided. Solid Insulation Materials is got the first rank whereas is the Gas Insulated Switchgear (GIS) is having the Lowest rank.

The increasing diffusion of high-voltage electrical assets in the field of aviation and aerospace sectors, due to the transition towards electrified transportation, brings significant challenges related to electrical insulation that need to be addressed. This work proposes a procedure to obtain reliable and partial discharge-free designs of aviation/aerospace electrical and electronic components, which stem from the recently developed three-leg approach. A partial discharge (PD) inception model that contains an explicit dependence on pressure is proposed and validated through a wide range of pressure levels ranging from 0.05 to 3 bar in air and CO2. Model fitting to measured partial discharge inception voltage (PDIV) values appears to be very good in air as well as CO2 environments; therefore, it can be speculated that the proposed approach can be used to predict PDIV in the case of solid insulation systems at different operating pressures, enabling PD-free insulation system designs to be carried out.

We determined the reference characteristics of the loss tangent and the real component of the complex permittivity of the cellulose-insulating oil–water nanodroplet nanocomposite with a moisture content of 5.17% by weight in pressboard. Such a high moisture content was selected because a value close to 5% by weight is critical, and reaching it may lead to catastrophic transformer failure as well as contamination of the natural environment with poorly biodegradable mineral oil and products of its incomplete combustion. Based on the measurement results, the values of the loss tangent and the real and imaginary components of the complex permittivity of the power transformer insulation system, consisting of moistened pressboard and insulating oil, were determined according to CIGRE. These values were obtained for both factory-new and moistened mineral oil. It was found that oil moisture content has a significant impact on the tanδ characteristics of strongly moistened liquid–solid insulation in the lowest frequency range. In the intermediate frequency range, this effect gradually decreases and then practically disappears. In the frequency range above 50 Hz, the tanδ values depend on the moisture content in cellulose and on the geometrical parameters of the insulation components in the CIGRE system, and do not depend on the oil moisture content. The influence of oil moisture on the estimation of cellulose moisture content becomes noticeable starting from a water content of 2% in pressboard. This should be taken into account in insulation condition analysis and in moisture level estimation in order to detect a critical state threatening catastrophic failure of a power transformer. It was also determined that the real component of the complex permittivity depends only weakly on oil moisture, and only in the low-temperature and low-frequency ranges. In contrast, the imaginary component of the complex permittivity depends on oil moisture practically in the same way as the loss tangent of the power transformer insulation system.

Insulation failure in solid dielectrics poses a great challenge to the safe operation of power equipment. In order to analyze the causes and mechanisms of different degradation processes in insulation materials, this paper builds an experimental platform to simulate the degradation of epoxy resin insulation defects. The degradation of conductive and non-conductive electrical trees under alternating current superimposed direct current voltage was studied. Experimental results show that conductive electrical trees have faster insulation failure times. Non-conductive electrical trees do not lead to insulation failure immediately after developing contact with the ground electrode, and still maintain insulation of the order of 102 s. Partial discharges are the cause of the growth of conductive trees, but not the non-conductive ones. A dimensionless phase-field simulation method is proposed to regulate the electrical tree development process through state parameters. The simulation results indicated that the development of two types of electrical trees is influenced by the strength of the electric field. When the electrostatic energy is not sufficient to cross the body free energy barrier, insulation degradation occurs as a non-conductive electrical tree. This paper provides new ideas for simulating insulation material degradation, which helps to understand the mechanisms of different insulation degradation types from an energy standpoint.

The increasing demand for power infrastructure has intensified the need for sustainable switchgear manufacturing, particularly in emerging markets like India. This paper presents a critical review of carbon emission mitigation strategies in the switchgear industry, with a focus on life-cycle assessment (LCA) as a guiding framework. It explores the transition from sulfur hexafluoride (SF₆)-based systems to environmentally friendly alternatives such as clean air, vacuum, and solid insulation technologies. The review highlights global innovations by leading manufacturers including Siemens, Hitachi Energy, ABB, and Eaton, and contrasts these with the infrastructural, regulatory, and financial challenges faced by the Indian switchgear sector. Technological advancements—such as IoT-enabled monitoring systems, laminated bus plate designs, and hybrid switchgear—are examined for their role in reducing greenhouse gas emissions. The study underscores the importance of LCA in quantifying environmental impacts across product life cycles and calls for stronger policy support and investment in sustainable innovation to accelerate carbon neutrality in switchgear manufacturing.

The paper presents a hybrid intelligent expert diagnostic system (HIESD) of power transformer (PT) subsystems realized on the basis of integration of measuring and computing hardware and software complexes into a single functional architecture. HIESD performs online diagnostics of four main subsystems of PT: 1—insulating (liquid and solid insulation); 2—electromagnetic (windings, magnetic conductor); 3—voltage regulation; and 4—high-voltage inputs. Computational complexes and modules of the system are connected with the real object of power grids, 110/10 kV substation, which interact with each other and contain a relational database of retrospective offline data of the PT “life cycle” (including test and measurement results), supplemented by online monitoring data of the main subsystems, corrected by high-precision test measurements; analytical complex, in which the work of calculation modules of the operational state of PT subsystems is supplemented by predictive analytics and machine learning modules; and a knowledge base, sections of which are regularly updated and supplemented. The system architecture is tested at industrial facilities in terms of online transformer diagnostics based on dissolved gas analysis (DGA) data. Additionally, a theoretical model of diagnostics based on the electromagnetic characteristics of the transformer, which takes into account distorted and nonlinear modes of its operation, is presented. The scientific significance of the work consists of the presentation of the following new provisions: Methodology and algorithm for diagnostics of electromagnetic parameters of ST, taking into account nonlinearity and non-sinusoidality of winding currents and voltages; formation of optimal client–service architecture of training models of hybrid system based on the processes of data storage and management; and modification of the moth–flame algorithm to optimize the smoothing coefficient in the process of training a probabilistic neural network

We introduce a novel lateral transistor architecture, the semiconductor-free-space gate transistor (SFGT), in which the conventional solid dielectric is replaced by a semiconductor-free-space gate configuration with sub-100 nm fin channels and dual side gates. This work presents the first demonstration of free-space gating in wide and ultrawide bandgap semiconductors, achieving performance on par with oxide-gated transistors. SFGTs fabricated using β-Ga2O3 exhibit subthreshold slopes below 200 mV/dec, high drain current exceeding 250 mA/mm, hysteresis under 230 mV, ION/IOFF ratios above 106, and breakdown voltages over 500 V. The absence of a solid dielectric layer, combined with the open gate geometry, enables direct access to the gate region for external electric field modulation and threshold voltage tuning, while mitigating the detrimental effects of charges and trap states in conventional dielectrics. These results show the potential of SFGTs for future memory, sensing, and power applications.

Solid-liquid contact electrification (CE) has recently emerged as a powerful means of initiating interfacial chemical reactions via charge transfer. Fluorinated ethylene propylene (FEP) and polytetrafluoroethylene (PTFE) are frequently employed as solid dielectrics owing to their fluorine-rich surfaces, which exhibit strong electron-withdrawing characteristics. However, their high environmental cost and poor surface modifiability hinder the broader adoption of contact-electro-chemistry (CE-Chemistry). Here, we report a low-cost and tunable dielectric alternative based on silicon powder, surface-functionalized with fluorinated alkyl chains to mimic the interfacial properties of conventional fluoropolymers. Fluorinated silicon powders (F-Si) were synthesized via a mild self-assembly approach using 1H,1H,2H,2H-perfluorodecyltriethoxysilane. The resulting F-Si powders exhibited a 30-fold enhancement in methyl orange degradation efficiency compared to unmodified silicon, and a 4-fold improvement in phenol degradation relative to size-matched FEP powder. In contrast, aggressive fluorination via piranha-assisted pretreatment (P-F-Si) induced particle aggregation and loss of CE reactivity, highlighting the importance of controlled surface engineering. Furthermore, CE-Chemistry enabled the first noble-metal-free oxidation of I- to I3 -, establishing a low-energy, cost-effective paradigm for catalytic iodine conversion. Together, these advances provide a sustainable materials design framework for CE-Chemistry, with broad implications for scalable, green chemical transformation technologies.

Abstract Solid–liquid contact electrification (CE) has recently emerged as a powerful means of initiating interfacial chemical reactions via charge transfer. Fluorinated ethylene propylene (FEP) and polytetrafluoroethylene (PTFE) are frequently employed as solid dielectrics owing to their fluorine‐rich surfaces, which exhibit strong electron‐withdrawing characteristics. However, their high environmental cost and poor surface modifiability hinder the broader adoption of contact‐electro‐chemistry (CE‐Chemistry). Here, we report a low‐cost and tunable dielectric alternative based on silicon powder, surface‐functionalized with fluorinated alkyl chains to mimic the interfacial properties of conventional fluoropolymers. Fluorinated silicon powders (F‐Si) were synthesized via a mild self‐assembly approach using 1H,1H,2H,2H‐perfluorodecyltriethoxysilane. The resulting F‐Si powders exhibited a 30‐fold enhancement in methyl orange degradation efficiency compared to unmodified silicon, and a 4‐fold improvement in phenol degradation relative to size‐matched FEP powder. In contrast, aggressive fluorination via piranha‐assisted pretreatment (P‐F‐Si) induced particle aggregation and loss of CE reactivity, highlighting the importance of controlled surface engineering. Furthermore, CE‐Chemistry enabled the first noble‐metal‐free oxidation of I − to I 3 − , establishing a low‐energy, cost‐effective paradigm for catalytic iodine conversion. Together, these advances provide a sustainable materials design framework for CE‐Chemistry, with broad implications for scalable, green chemical transformation technologies.

In high-humidity environments, the epoxy resin solid insulation materials of high-frequency transformers are prone to aging, resulting in varying degrees of deterioration in the material’s dielectric properties and other aspects. To enhance the adaptability of epoxy resin in high humidity environments, this paper, based on the molecular dynamics simulation method, establishes epoxy resin-based nanocomposites with doped nanofillers: a pure epoxy resin model and three epoxy resin models, respectively, doped with carbon nanotubes, graphene(GR), and SiO2. Based on the above models, using LAMMPS-17Apr2024, the thermal diffusion coefficients (thermal conductivity and specific heat capacity), glass transition temperatures, and dielectric constants under different moisture contents are calculated. The results show that the various properties of the epoxy resin nanocomposites doped with nanofillers have been improved to varying degrees. Among them, the GR/epoxy resin composite model shows the most significant improvements in thermal conductivity, thermal diffusivity, and glass transition temperature, and the SiO2/epoxy resin composite model has the best dielectric properties. Considering the high-temperature operation conditions and heat dissipation requirements of the high-frequency transformer, the GR-enhanced epoxy resin becomes the optimal filler choice.

In the context of an ultrafast laser interacting with solids, temperature plays a special role in the transformation processes. Some of these processes can be thermally activated, while others can be either solely driven or constrained by temperature—such as refractive index change (fictive temperature), nanopore erasure, micro-bubble formation, and phase transition-like crystallization. The objective of this paper is to use a recently developed analytic approximation to understand the limitations imposed by the spatial temperature distribution and its evolution over the writing time, based on the key laser parameter combinations, and subsequently determine the boundary conditions of these parameters.

Furfural (FF), anintermediate aldehydecompound, can serve asan indicator of the extent of the Maillard reaction on heat-inducedfood processing and storage, as well as for the aging assessment ofthe solid insulation of oil-immersed transformers because it is formedby the degradation of cellulosic insulation. By considering the conceptsof green analytical chemistry, a new furfural–bis­(4-aminophenyl)disulfide (APDS) colorimetric chemosensory assay, based on the Stenhousereaction between furfural and APDS, was developed for the quantificationof furfural by utilizing UV spectroscopy and colorimetric analyses.A strong correlation between UV–vis absorbance and furfuralconcentrations was observed, which confirmed the high sensitivity(0.00024 mM furfural) of the reaction system. The color change at0.005 mM of furfural was noted by the naked eye. This was a uniqueand highly selective phenomenon because only furfural shows UV absorbanceand color change within 450–600 nm of UV radiation, unlikeother aromatic and aliphatic aldehydes. The highly sensitive methodwas applied for the qualification of 0–0.01 mM (0–1ppm) of furfural in the power transformer insulating fluid. An APDSstrip formulated with polyethylene glycol was used as the chromatographypaper. This study demonstrates the successful surface Stenhouse couplingbetween furfural and APDS, as confirmed by X-ray photoelectron spectroscopyanalysis. Therefore, this liquid- and solid-based assay is a novel,green analytical method as it uses safer solid APDS instead of toxicliquid aniline that is generally used in conventional methods. Inaddition, the method is simpler, which makes the on-site analysispossible.