High-voltage Electrical Equipment Research Articles

Innovative Approach for Detecting Early-Stage Partial Discharges in Instrument Transformers via Ultrasound and Random Forest Analysis

This article introduces a novel technique for detecting and classifying Partial Discharges in Instrument Transformers, addressing the gradual breakdown of external insulation in high-voltage electrical equipment through ultrasound measurements. The use of hand-held probe-microphones for ultrasonic sensing gains prominence for its versatility and online diagnostic capabilities. The proposed method combines insights into partial discharge types and the pollution level within the equipment, thereby transforming ultrasonic readings into useful information and facilitating informed decision-making. Laboratory tests simulate real-world conditions to which current and voltage transformers of 145 kV and 245 kV are subjected. These tests result in ultrasonic and apparent charge measurements, also known as Phase-Resolved Partial Discharges (PRPD). A random forest model achieves over 92 % accuracy in classifying ultrasonic signals into eight class: normal, light partial discharge, light corona, corona, light superficial, light saline pollution, moderate saline pollution and heavy saline pollution; enhancing the understanding and predictive maintenance of instrument transformers.

The design of a linear voltage divider based on metal oxide arresters.

In recent years, linearization technology for nonlinear devices has become a hot topic in many fields. In this study, a linear voltage divider based on metal oxide arresters was designed by combining linearization technology and electrical measurement technology to solve the objective problems of online voltage monitoring. These problems include high difficulty in equipment installation, low measurement accuracy, and poor economic benefits. Based on a summary of linearization theory, the sufficient and necessary conditions for the linearization of the voltage divider were deduced in detail. The relevant circuit simulations were conducted, along with voltage divider experiments under power frequency AC voltage, operating overvoltage, and lightning overvoltage. The results revealed that the voltage divider was able to realize linearized measurements and meet the relevant standards of online voltage monitoring. The measurement errors were concentrated in the transition region between the pre-breakdown region (small current region) and the breakdown region (nonlinear region) in the volt-ampere characteristic curve. The main influencing factor of errors was the consistency of the nonlinear characteristics of the high- and low-voltage arms of the voltage divider. The voltage divider designed in this study can be applied in many scenarios, such as power plants, substations, high-voltage electrical equipment manufacturing plants, and high-voltage laboratories.

FPGA-Based VFF-RLS Algorithm for Battery Insulation Detection in Electric Vehicles

As the adoption of electric vehicles (EVs) continues to rise, attention has switched to ensuring the safety of EV operations. The exponential growth in battery technology over the past several years has changed the face of energy storage and sparked a revolution in several industries. The degradation of battery insulation during regular use is a significant concern. The high voltage (HV) and current levels in HV electric vehicles pose a significant electrical threat.The advancement of electric vehicle technology has led to an increasing presence of HV electric equipment throughout the vehicle. The insulation strength and early health status detection of the batteries are essential in ensuring safety in EVs. This paper studies the different insulation detection techniques and the development of adaptive filter (AF) algorithms based on field-programmable gate arrays (FPGAs) for insulation detection. FPGAs are amongst the most accurate and fast detection techniques among all the insulation detection techniques used so far in electric vehicles. This study proposes an FPGA-based VFF-RLS algorithm for effectively implementing insulation detection in EVs. The experimental test results using FPGAs demonstrate that the proposed method can rapidly monitor changes in insulation resistance (IR). The VFFRLS-based FPGA technique works sufficiently well to reduce errors when dealing with variations in voltage and resistance conditions at the battery terminals.

Robust approximation rules for critical electric field of dielectric gas mixtures

A semi-analytic method for quickly approximating the density-reduced critical electric field for arbitrary mixtures of gases is proposed and validated. Determination of this critical electric field is crucial for designing and testing alternatives to SF6 for insulating high voltage electrical equipment. We outline the theoretical basis of the approximation formula from electron fluid conservation equations, and demonstrate how for binary mixtures the critical electric field can be computed from the transport data of electrons in the pure gases. We demonstrate validity of the method in mixtures of N2 and O2, and SF6 and O2. We conclude with an application of the method to approximate the critical electric field for mixtures of SF6 and HFO1234ze(E), which is a high interest mixture being actively studied for high voltage insulation applications.

A High-Voltage-Specialized Direct-Current Triboelectric Nanogenerator for Air Purification.

Human health and the environment face significant challenges of air pollution, which is predominantly caused by PM2.5 or PM10 particles. Existing control methods often require elevated energy consumption or bulky high-voltage electrical equipment. To overcome these limitations, a self-powered, convenient, and compact direct current high-voltage triboelectric nanogenerator based on triboelectrification and electrostatic breakdown effects is proposed. By optimizing the structure-design of the direct current triboelectric nanogenerator and corresponding output voltage, it can easily achieve an output voltage of over 3kV with a high charge density of 320 µC m-2 . A power management circuit is designed to overcome the influence of third domain self-breakdown, optimize 92.5% amplitude of voltage shake, and raise 5% charge utilization ratio. With a device size as tiny as 2.25 cm3 , it can continuously drive carbon nanowires to generate negative ions that settle dust within 300 s. This compact, simple, efficient, and safe high-voltage direct current triboelectric nanogenerator represents a promising sustainable solution. It offers efficient dust mitigation, fostering cleaner environments, and enhancing overall health.

Seismic Assessment of Electrical Equipment in Power Substations: A Case Study for Circuit Breakers

Electric power is essential in post-earthquake periods for the continuous functionality of disaster management and emergency services. In addition, interruption of electric power can cause significant economic losses due to downtime of critical facilities. Therefore, it is very important to maintain seismic safety of electric power systems and components. There are existing seismic regulations and standards regarding electric power systems, especially in the United States of America (USA) and Europe. A similar regulation has been prepared recently in Türkiye, which is a country in a seismically active region. This study focuses on the current state of practice regarding the seismic assessment of electrical equipment in power stations and implementation of the regulations on seismic qualification of these systems. Among many electrical equipment, circuit breakers have been selected for case study. The seismic assessment of the selected high voltage equipment has been performed according to the new regulation under the seismic hazard specifically defined for Türkiye. The case study experiment presents the new methodology in evaluating and classifying the seismic response of high voltage electrical equipment and provides insight to the expected behaviour of circuit breakers under earthquake induced action.

High-temperature properties of dry air used as arc quenching medium and its mixture with vaporized C2F4 : reaction products and critical reduced electric field strength at 300–3000 K

Recently, electric power equipment manufacturers released a joint statement with the aim of developing high-voltage electrical equipment completely free of fluorinated gases such as fluoroketones and fluoronitriles, which are considered as alternatives to SF6 and artificially produced compounds of F. This paper considers air as a typical gas present naturally in the environment to investigate its high-temperature properties, including an air mixture with C2F4 vapor injected from a polytetrafluoroethylene nozzle, for application as an arc-quenching medium in a high-voltage circuit breaker equipped with a nozzle. Chemical composition results for the reaction products at 300–3000 K show that the admixture of C2F4 vapor causes a decrease in the molar number of O2 contained in the air, owing to the production of O-containing compounds such as CO2 and CO . Additionally, the results reveal that the admixture of C2F4 vapor lead to the production of CF4 as the predominant F-containing compound. Furthermore, the boundary condition for O2 production in terms of O2 molar number XO2 and C2F4 molar number XC2F4 is formulated. Such evaluation of the mixture composition enables the determination of a reduced effective collision ionization coefficient αˉ/N and a critical reduced electric field strength Ecr/N , resulting in αˉ/N = 0. The strength Ecr/N for the mixture with 30%–100% C2F4 molar fraction rises to approximately 150 Td (1 Td = 1 ×10−21 V m2) over 300–3000 K, which is 20–50 Td higher than that for high-temperature air unmixed with C2F4 vapor. The variation in Ecr/N is discussed in terms of predominant electron impact processes and the electron energy distribution function in the mixture.

Assessment of the Arc Resistance of 3D-Printed Insulation Materials for Outdoor High-Voltage Applications

High-voltage electrical equipment insulation often uses composite materials like epoxy resin, cross-linked polyethylene, polyurethane, and silicone rubber as encapsulation. 3D printing technology offers a more efficient and cost-effective solution, producing intricate elements without cutting and casting. Research shows that 3D printed materials have comparable properties to polymer-based insulation, but further testing is needed to evaluate their resistance to harsh environmental conditions. This research investigates the arc resistance properties of 3D printed insulation materials for outdoor high-voltage applications, assessing their suitability for outdoor applications. The wet and dry arc resistance tests were performed in accordance with ASTM D495-99 and IEC-60587. The present work investigated three varieties of samples: polylactic acid, epoxy resin, and silicone rubber. The results of the tests reveal that polylactic acid test samples have average wet and dry arc resistance times of 2.5 hours and 1.4 seconds, which is less than silicone rubber and epoxy resin. Additional research is required to comprehend the behavior of arc formation in polylactic acid insulation materials for high-voltage 3D printing applications.

Significantly Improve the Thermal Conductivity and Dielectric Performance of Epoxy Composite by Introducing Boron Nitride and POSS.

Dielectric materials with superb thermal and electrical properties are highly desired for high-voltage electrical equipment and advanced electronics. Here, we propose a novel strategy to improve the performance of epoxy composites by employing boron nitride nanosheets (BNNSs) and γ-glycidyl ether oxypropyl sesimoxane (G-POSS) as functional fillers. The resultant ternary epoxy composites exhibit high electrical resistivity (1.63 × 1013 Ω·cm) and low dielectric loss (<0.01) due to the ultra-low dielectric constants of cage-structure of G-POSS. In addition, a high thermal conductivity of 0.3969 W·m-1·K-1 is achieved for the epoxy composites, which is 114.66% higher than that of pure epoxy resin. This can be attributed to the high aspect ratio and excellent thermally conductive characteristics of BNNSs, promoting phonon propagation in the composites. Moreover, the epoxy composite simultaneously possesses remarkable dynamic mechanical properties and thermal stability. It is believed that this work provides a universal strategy for designing and fabricating multifunctional composites using a combination of different functional fillers.

Enhancing grid protection: The crucial role of resistive-type superconducting fault current limiters in transmission line current differential relays

Superconducting fault current limiters (SFCLs) offer an efficient means of limiting fault currents and supporting system reliability. However, they weaken the fault characteristics and reduce the sensitivity of traditional relay protection. The seamless integration of SFCLs with protective relays remains a complex and under-explored area, impeding their widespread industrial adoption. In parallel, current differential protective (CDP) relays are almost the primary protection for all high-voltage electrical equipment and are the cornerstone of global power system security. This paper fills a critical knowledge gap by researching the intricate interaction between resistive superconducting fault current limiters (R-SFCLs) and current differential protective relays. Our investigation commences with a comprehensive mathematical analysis, while researching the influence of R-SFCLs on CDP operation. Subsequently, we conduct a series of comparative experiments using the Matlab Simulink software platform. These tests evaluate the sensitivity, dependability, and security of CDPs in scenarios with and without R-SFCLs. The simulation results not only confirm the accuracy of our analytical framework but also shed light on the multifaceted relationship between R-SFCLs and CDPs. This research contributes to a deeper understanding of how R-SFCLs can be effectively integrated into power systems, offering a roadmap for enhancing grid protection.

Using copper-coated round rod electrodes at various depths in freshwater marshes

Purpose: High-voltage electrical equipment requires a grounding installation in order to protect lives in freshwater swamps with a hydrogen potential of 6.75. To build a grounding structure, it is required to know the resistance value and grounding materials, namely copper-coated rod electrodes at different depths.&#x0D; Research methodology: The research was conducted in a freshwater swamp close to the shampooing substation using field observations and direct measurement of soil resistance values, followed by a literature review and comparisons using COMSOL simulation and FEM Analysis.&#x0D; Results: The results of direct research and simulations indicate that in order to accomplish a grounding resistance value &lt; 5 ohms according to the PUIL 2011 standard for a single rod system made of copper, it is necessary to optimize the depth of the grounding electrode within a range of 10 meters, which differs from the simulation results of ground resistance measurement and the Comsol application. The percentage error is 1.05%.&#x0D; Limitations: This research analyzes the results of measurements and grounding analysis using Comsol Multiphysics at a depth of 1 meter for a particular type of copper-coated round rod electrode at depths of 1, 1.5, and 2 meters.&#x0D; Contributions: The results of the study offer information on the usefulness of grounding resistance in freshwater wetlands with a pH greater than 6, where several rod electrode types are utilized to compare future research.

A Denoising Method of Partial Discharge Signal Based on Improved SVD-VMD

A denoising method combined with singular value decomposition (SVD) and Variational mode decomposition (VMD) is proposed to eliminate noise in on-site partial discharge (PD) signals from high-voltage electrical equipment. In the Fourier transform power spectrum, periodic narrowband interference was eliminated after SVD was offered to determine the number of singular values of periodic narrowband interference. Then, the PD signal was decomposed into K intrinsic mode function components by VMD. The empirical mode decomposition method was used to determine the K value of white noise’s intrinsic mode function components. An improved 3σ criterion threshold method was proposed to eliminate the residual noise in the PD signal. The denoising method was compared with the other two methods to analyze the denoising effect on the simulation and experimental PD signal. This paper’s denoising method can eliminate periodic narrowband interference and white noise in different PD signals of cavity discharge, corona discharge, and those from the motors’ coil. The denoised PD pulse waveform has a higher signal-to-noise ratio and normalized correlation coefficient and a lower mean square error, indicating that the waveform’s original characteristic remains.

Characterization of Heat-Resistant Insulating Impregnating Varnish Based on Bismaleimide/Diamine Copolymer

With the development of high-voltage electrical equipment towards the direction of higher power density and higher voltage level, it will resulting in the temperature-resistant grade of insulating dip varnish. Bismaleimide (BMI) resin used as the matrix resin of dip varnish solution is widely applied due to its good aging resistance, mechanical properties and dielectric properties. Due to the imide ring structure in BMI resin structure, the bonding energy of chemical bonds in the molecule is higher. The resin reacts less at lower temperatures, resulting in the difficulty of forming and processing. The high crosslinking density of condensates results in unsatisfactory mechanical properties of BMI resin and presents a poor toughness. Therefore, this paper uses Michael addition reaction to prepare branched resin with large free volume from binary amine and BMI resin, and explores various properties of its cured products. The results show that: Using different kinds and different contents of binary amines, its insulation performance was further improved. MT-cured sample had the best comprehensive performance, with a minimum dielectric constant of 3.24. The minimum dielectric loss of BAPP cured sample was 0.00135. The maximum volume resistivity of FDA sample was 2.46×1015 Ω·m and the maximum breakdown field strength of BAPP sample was 29.83 kV/mm; The mechanical properties were significantly improved, and the maximum mechanical strength of the MT samples reached 174.63 MPa.

Research on the performance of green and environmentally friendly epoxy resin impregnated paper 110 kV current transformer

As an important high-voltage electrical equipment in the substation, the performance stability of high-voltage current transformers is directly related to the safe operation of the power grid. The insulating medium of the traditional oil-immersed current transformer is an oil-immersed paper structure. When the oil-immersed current transformer malfunctions, it is easy to cause fire and explosion, resulting in very serious consequences. If the transformer with the epoxy resin impregnated paper insulation medium is used, there is no oil and gas inside; thus, it has high reliability, which greatly reduces the risk of fire and explosion. Based on this, considering the application research on the high-voltage current transformers epoxy resin impregnated paper technology, this paper mainly analyzes some precautions for the application of epoxy resin impregnated paper technology to the high-voltage current transformers from three aspects: the research on the insulation performance of the epoxy resin impregnated paper transformers, the research on the mechanical properties, and the research on the relevant experimental methods of the epoxy resin impregnated paper technology application to the high-voltage current transformers.

Improvement of surface insulating performance for polytetrafluoroethylene film by atmospheric pressure plasma deposition

The surface flashover phenomenon across a vacuum-dielectric interface severely limits the service life and operational reliability of high voltage electrical equipment. Surface modification by atmospheric pressure plasma treatment is a promising method to improve the surface insulating performance of polymers. In order to explore the mechanism of plasma processing on the vacuum flashover characteristics of polymer materials, atmospheric pressure plasma deposition was used to treat polytetrafluoroethylene (PTFE) film. The surface parameters under different processing conditions, such as surface chemical composition, surface resistivity, surface charge decay and trap distribution, were tested and analyzed. The space charge distribution of PTFE and the flashover voltage in vacuum were measured. The results show that Si–O–Si and Si–OH groups are introduced on the surface of PTFE, and the characteristic peaks of PTFE are gradually weakened with the increase of processing time. The surface trap density increases and more traps with lower energy level arise with longer processing time. The plasma deposition changes the space charge distribution in PTFE body, and leads to positive charge accumulation inside the sample. The flashover field strength respectively increases by 15% and 70% in direct current (DC) voltage and microsecond pulse voltage after plasma deposition. The rapid dissipation of surface charge is the main reason for pulse flashover voltage enhancement, while the increase of surface leakage current due to lower surface resistivity and space charge accumulation in PTFE body make the DC flashover voltage reach the saturation point. Therefore the surface insulating and body performance of polymer materials after plasma modification processing should be considered comprehensively based on different applications.

Assessment of efficiency improvement reserves of maintenance and repair systems of high-voltage electrical equipment of industrial enterprises

The problems of choosing a strategy for the maintenance of the equipment of the power supply system of an industrial enterprise, taking into account the risk its failure and the problem of distributing the volume of the repair program in order to reduce maintenance costs and, accordingly, the cost of production, are considered. A method for assessing the magnitude of risk for the technological process of an industrial enterprise of the metallurgical industry, taking into account the power supply scheme of the electric receiver, is proposed. Special attention is paid to taking into account the influence of the power supply system of an industrial enterprise on the operation of final electrical receivers directly involved in the technological process. An example of using the proposed technique in a real power supply system with available statistical data on its failures is considered. The article formulates an approach to assessing the risk of failure of elements of the power supply network of an industrial enterprise, taking into account the operational scheme of power supply, and also shows the insufficiency of assessing the risk of power supply failures only from the failure of circuit elements through which electric power is directly transmitted to the electric receiver in question.

Review of the Digital Twin Technology Applications for Electrical Equipment Lifecycle Management

Digital twin is one of the emerging technologies for the digital transformation of the power industry. Many existing studies claim that the widespread application of digital twins will shift the industry to a principally new level of development. This article provides an extensive overview of the industrial application experience of digital twin technologies for solving the problems of modern power systems with a particular focus on the task of high-voltage power equipment lifecycle management. The latter task contours one of the most promising areas for the application of the digital twins in the power industry since it requires deep analysis of the technological processes dynamics and the development of physical, mathematical and computer models that cover all the potential benefits of the digital twin technology. At the moment, there is a lack of reliable data on the problems of assessing and predicting the technical state of high-voltage power equipment. The use of digital twin technology in modern power systems will allow for aggregating data from a variety of real objects and will allow the automatization of collecting and processing of big data by implementing artificial intelligence methods, which will ultimately make it possible to manage the life cycle of the power equipment. The article puts to scrutiny the industrial experience of digital twins creation, considering the technical solutions suggested by the largest manufacturers of electrical equipment. A classification of digital twins, examples and main features of their application in the power industry, including the problem of managing the life cycle of high-voltage electrical equipment, are considered and discussed.

The Influence of Antioxidants on the Resistance of Rapeseed Oil of High-Voltage Electrical Equipment to Oxidation

The Influence of Antioxidants on the Resistance of Rapeseed Oil of High-Voltage Electrical Equipment to Oxidation

Research on Key Technologies for Measuring the Recovery Rate and Gas Measurement of SF6 Gas On-site Maintenance Surface

Carrying out full lifecycle management of SF6 gas recovery, purification, and recycling, developing new digital control technologies, and eliminating SF6 gas emissions from the source are of great significance for achieving the “dual carbon” goal. Given the low level of digital control of SF6 gas at present, especially in the situation, the SF6 gas recovery rate, the effective volume of the gas chamber, and gas weight cannot be accurately measured at an on-site inspection surface, this paper carries out research on SF6 gas recovery rate measurement at on-site inspection surface and key technologies of gas measurement. An intelligent online monitoring device such as SF6 gas recovery rate and effective chamber volume of high voltage electrical equipment was developed, which can quickly identify SF6 gas density, recovery rate, effective chamber volume, weight, and other parameters in high voltage electrical equipment, and evaluate the detection methods such as gas recovery rate and effective chamber volume. The results show that when the recovery rate was about 96.5%, the maximum positive deviation between the recovery rate measured by the detection device and that measured by the weighing method was 0.32% and the maximum negative deviation was -0.24%, both of which are less than 0.50%. When the container to be tested was 1000 L, the maximum indication error was -1.51%, which can meet the requirements of digital control in the SF6 gas recycling and reuse process of high-voltage electrical equipment.

Electrodynamic withstand and effects of short-circuit currents on high-voltage electrical equipment

The analysis of simplified expressions allows us to estimate the electrodynamic effects of short-circuit currents on the main elements of a power electrical station and substation, which include busbars, high voltage circuit-breakers, disconnectors, electrical machines and transformers. Examples of calculations of magnetic field induction, mechanical forces and pressures that determine the electrodynamic withstand of electrical equipment are given. Simplified qualitative calculations allow us to assess the impact of key parameters on the selection of appropriate elements and the possible range of their changes during the design, operation and modernization at the preliminary design stage.