High Voltage Transformer Research Articles

Lightning impulse breakdown behavior of natural ester and modified natural ester under long oil gap: An experiment and first-principles simulation analysis

The investigation of lightning impulse (LI) breakdown characteristics in long oil gaps with insulating liquids is of utmost importance for the design of high-voltage, large-capacity transformers. This study focuses on analyzing the negative LI breakdown characteristics of two types of insulating oils, namely high viscosity natural ester soybean oil (SO) and low viscosity modified natural ester palm fatty acid ester (PFAE), under long oil gap conditions. The research includes testing and analyzing the voltage and current waveforms, LI breakdown voltage, and streamer discharge development speed of these liquids across oil gaps ranging from 25 mm to 105 mm. The findings demonstrate that the breakdown voltage of both insulating oils tends to increase as the oil gap distance widens. At a 25 mm gap, the average breakdown voltage of PFAE is not significantly different from that of SO. However, at a 105 mm gap, the average breakdown voltage of PFAE surpasses that of SO by 46.29%. Weibull distribution analysis is applied to the LI breakdown voltage data of the two insulating liquids, resulting in empirical formulas for breakdown voltage as a function of oil gap width at failure probabilities of 1%, 50%, and 90%. The discharge development rate of PFAE is lower than that of SO, especially in the oil gap of 105 mm. With the increase of the oil gap, the streamer development rate of the two insulating oils showed a trend of increasing. Using density functional theory based on first principles, the study investigates changes and discrepancies in parameters such as ionization potential, electron affinity, softness, excitation energy, and molecular surface electrostatic potential of the two insulating liquids with varying electric field strengths. The atomic and molecular scale analysis reveals the primary factors contributing to the contrasting macroscopic lightning shock breakdown characteristics of SO and PFAE. The comprehensive combination of experimental and simulation results suggests that PFAE exhibits greater potential for implementation in high-voltage, large-capacity transformers compared to SO. This study aims to bridge the gap in knowledge regarding the LI breakdown characteristics of different natural esters in long oil gaps. The experimental and theoretical findings presented in this paper provide a foundation for the practical application of natural esters and modified natural esters in high-voltage and large-capacity transformers.

Effect of an electromagnetic field generated by power infrastructure on the spatial orientation of developing sea trout embryos Salmo trutta Linnaeus, 1758

In recent decades, rapid technological advancements have led to a growing influence of anthropogenic electromagnetic fields on aquatic ecosystems. These fields predominantly stem from energy infrastructure facilities such as wind farms, high-voltage lines, underwater transmission cables, and power plants. As a result, there has been increasing interest in understanding the effects of heightened electromagnetic fields on aquatic ecosystems and their inhabitants, including developing fertilized eggs. This study focused on examining the effects of electromagnetic fields generated by high-voltage lines and power transformers, which are integral to transmission nodes and power plants, on the directional axis of symmetry in sea trout Salmo trutta (Linnaeus, 1758) embryos and their survival rates. The research was carried out at “PGE Dolna Odra in Nowy Czarnów”, one of Poland’s largest power plants (53°12′34′′ N, 014°28′16′′ E). Two experimental sites were selected, with electromagnetic field values ranging from 1.36 to 5.28 μT at the first site and 8.97 to 14.18 μT at the second site. A control sample was also established in an area unaffected by anthropogenic electromagnetic fields. The study findings revealed that electromagnetic fields originating from energy infrastructure facilities significantly affect the spatial orientation of sea trout embryos. The embryos’ response was influenced to be influenced by both the strength and direction of the electromagnetic fields. At the first test site, lower field values caused deviations from the natural alignment axis in the geomagnetic field (north-south), resulting in a shift towards the primary field source. In contrast, the second test site, with higher electromagnetic field values, showed no significant spatial orientation in embryo alignment. Additionally, the study highlighted that higher electromagnetic field values accelerated the rate of embryogenesis but also led to an increased mortality rate among sea trout embryos.

Research on welding defect examination technique based on phased array ultrasonic for high voltage transformer oil tank welds

Oil tank of high voltage transformer plates. During welding and operation, defects such as incomplete fusion, incomplete penetration , air holes and cracks may be produced which influence the integrity and density of the welds and the whole tank. In order to test the integrity of the shell weld of high-pressure transformer box and ensure no leakage of transformer oil, the phased array testing technology is used to detect the defects of the butt weld of the transformer oil tank. The characteristics of weld defect detection under the condition of incomplete penetration were studied, and the sound beam accessibility, process selection principle and probe selection principle were theoretically analyzed. The test tests were carried out on the artificial samples of the butt weld of the transformer oil tank plate. The results show that the phased array can effectively detect the defects in the weld of transformer tank shell under the condition of incomplete welding, and the imaging results are intuitive and easy to judge, which can effectively evaluate the integrity of transformer tank weld. During the process selection, the probe-wedge combination with appropriate front distance and detection Angle should be selected according to the wall thickness, weld penetration depth and crown width of the transformer oil tank. During defects judgment, the interference of structure echo wave and incomplete penetration area should be considered. The assistant defect positioning analysis based on incomplete penetration is also suggested.

Enhancing microwave oven performance and transformer quality through efficient high voltage transformer cooling

This paper describes a method and device for effectively cooling a high voltage transformer inside a microwave oven, with the aim of swiftly removing heat generated during operation, hence improving both the microwave oven's and the transformer's performance and quality. The device incorporates corrugated tank surfaces, electrical connection lines with protrusions, and epoxy to prevent cooling oil leakage. The transformer is inserted into a designated tank and sealed to separate the coil and core from the outside environment, allowing for better cooling and protection against electrical shock. Additionally, an oil is injected to absorb heat generated by the high temperature of the core and coil. The effectiveness of this method is validated through the finite element method and computational fluid dynamics techniques. Numerical analysis revealed a significant decrease in the maximum temperature rise of the transformer by around 44.2?C. This finding suggests that transformer oil cooling is a more effective method for controlling temperature rise in microwave ovens compared to traditional cooling methods.

Numerical analysis of partial discharge ignition in H2 bubbles floating in dielectric oils, for High-Voltage Solid State Transformer applications

Numerical analysis of partial discharge ignition in H₂ bubbles floating in dielectric oils, for High-Voltage Solid State Transformer applications

Evaluation of thermal conductivity using nanofluids to improve the cooling of high voltage transformers

This paper was written to demonstrate the value of using nanofluids for cooling high power transformers while also providing current techniques for business and academia. A numerical analysis of the improvement caused by the cooling of a high voltage transformer using nanofluids has been done. A tank with a temperature source inside and a charge of mineral oil-barium titanate nanoparticles is used to study natural-convection. This study investigates the effects of variables on the thermal efficiency of the tank, including the thermal Rayleigh number and volume fraction. The results show that quenching varies with low and high Rayleigh thermal numbers and depends on the volume percentage of used nanoparticles. The effects were illustrated in thermal transfer rate representations as functions of the thermal Rayleigh number (Rat = 103 and 106) and the solid volume particle from the nanoparticles (0% ? ? < 10%). The findings showed that improving the solid volume particle of the nanoparticles by 10% causes the fluid being utilized to become more effectively conductive, which improves the rate of heat transfer by roughly 10% when compared to the case of the base fluid.

Calibration System for High-Voltage Transformers With Multiharmonic Distorted Waveforms

Calibration System for High-Voltage Transformers With Multiharmonic Distorted Waveforms

IMPROVEMENT OF THE METHOD OF DIAGNOSTICS OF HIGH-VOLTAGE TRANSFORMERS VOLTAGE BASED ON THE RESULTS OF CHROMATOGRAPHIC ANALYSES OF TRANSFORMER OILS

The relevance of the work is due to the need to improve methods for diagnosing high-voltage oil-filled voltage transformers with paper-oil electrical insulation, which makes it possible to solve the problems of monitoring the technical condition, finding the place and determining the causes of failure (malfunction), and predicting the technical condition of this equipment on the basis of appropriate diagnostic software. The aim of the work is to ensure the reliability of operation of high-voltage oil-filled voltage transformers with paper-oil electrical insulation by improving the method of their diagnosis based on the results of analyses of samples of mineral transformer oils by gas chromatography. In accordance with the research objective, the following tasks were solved: 1. Determine the content of such dissolved diagnostic components in samples of mineral transformer oils from high-voltage oil-filled voltage transformers of NKF-110, NKF-220, NKF-330 types as gases H2, CH4, C2H6, C2H4, C2H2, CO, CO2, O2, N2; additive "Ionol"; furan compounds (2-furyl alcohol; 2-furfural; 2-acetylfuran; 5-methyl-2-furfural) and the sum of their concentrations. 2. The basic procedures for diagnosing high-voltage oil-filled voltage transformers based on the results of analyses of mineral transformer oil samples with the determination of the content of dissolved diagnostic components in them were improved. For the diagnosis of high-voltage oil-filled voltage transformers based on the results of gas chromatographic analyses of samples of mineral transformer oils from this equipment, it is recommended to use the following methods: "Limit level of concentrations", "Tabular method", "Graphic images of defects", "ETRA", "Duval triangle", "Visual inspection after disassembly of high-voltage oil-filled voltage transformers". To determine the degree of danger of the development of the identified probable defects, the method of determining the "Relative growth rate of dissolved gas concentrations" can be used. The prospect of practical application of the results of the work is to ensure the reliability of operation of high-voltage oil-filled voltage transformers by improving the method of their diagnosis based on the results of analyses of samples of mineral transformer oils with simultaneous determination of the content of dissolved gases, the additive "Ionol", furan compounds by gas chromatography.

Mathematical Model of the Unbalanced Monopole Feed. Part 3. Gain

An integro-differential operator is specified that determines the longitudinal component of the electric field strength on the surface of the emitter conductor of an Unbalanced Monopole with Shunt Feed, created by the Base Current (BC). Analytical expressions are obtained that determine the parameters of an equivalent eight pole, which is the internal resistance of equivalent BC generators. The influence of the length of the counterweight conductors and the upper load of the high-voltage transformer on the efficiency and gain was studied.

HIGH-VOLTAGE MODULATOR FOR ION LINAC INJECTOR WITH SMOOTH PULSE DURATION CONTROL

The ion linear accelerators stable operation essentially depends on the ion injector. To ensure maximum capture of the ion beam injected into the accelerating structure, the injector must be able to adjust the beam parameters. The paper describes the developed new injector power supply system, built on modern assemblies, which allows smoothly changing the modulator pulse duration in the range of 300…2000 µs. The analysis was carried out and the shortcomings of the previous systems were eliminated. The expected increase in the accelerated ion beam current is 15…20%. Related results include a decrease in the parasitic load capacitances of pulsed devices, a reduction in size, and the rejection of high-voltage isolation transformers, which increases the reliability of the accelerator.

Investigation of Novel Solid Dielectric Material for Transformer Windings.

Improvement techniques aimed at enhancing the dielectric strength and minimizing the dielectric loss of insulation materials have piqued the interest of many researchers. It is worth noting that the electrical breakdown traits of insulation material are determined by their electrochemical and mechanical performance. Possible good mechanical, electrical, and chemical properties of new materials are considered during the generation process. Thermoplastic polyurethane (TPU) is often used as a high-voltage insulator due to its favorable mechanical properties, high insulation resistance, lightweight qualities, recovery, large actuation strain, and cost-effectiveness. The elastomer structure of thermoplastic polyurethane (TPU) enables its application in a broad range of high-voltage (HV) insulation systems. This study aims to evaluate the feasibility of using TPU on transformer windings as a solid insulator instead of pressboards. The investigation conducted through experiments sheds light on the potential of TPU in expanding the range of insulating materials for HV transformers. Transformers play a crucial role in HV systems, hence the selection of suitable materials like cellulose and polyurethane is of utmost importance. This study involved the preparation of an experimental setup in the laboratory. Breakdown tests were conducted by generating a non-uniform electric field using a needle-plane electrode configuration in a test chamber filled with mineral oil. Various voltages ranging from 14.4 kV to 25.2 kV were applied to induce electric field stress with a step rise of 3.6 kV. The partial discharges and peak numbers were measured based on the predetermined threshold values. The study investigated and compared the behaviors of two solid insulating materials under differing non-electric field stress conditions. Harmonic component analysis was utilized to observe the differences between the two materials. Notably, at 21.6 kV and 25.2 kV, polyurethane demonstrated superior performance compared to pressboard with regards to the threshold value of leakage current.

Multi-functional phase for precision sampling resistors for HVDC voltage transformer and efficient microwave absorption

Precision resistor performance has a direct impact on the detection accuracy of DC voltage transformers since it is a crucial component for signal sampling in high-voltage DC (HVDC) voltage transformers. The accuracy of the resistance is directly related to the performance of the slurry, which is sintered to produce the resistance. In this article, two different kinds of conductive fillers carbon-based and metal-based were created using the hydrothermal technique and high-temperature carbonization, and the matching resistance slurry and thick film resistors were made by compounding glass powder and organic carriers. The findings demonstrate the resistance slurry prepared using copper nanopowder as a conductive filler can achieve lower square resistance values and can be adjusted within the range of 124 Ω/□ -1503 Ω/□ by changing the solid content, and the square resistance is less affected by temperature. It can be used as a precision resistor for preparing high-voltage DC voltage transformers. Furthermore, the prepared functional phase materials also exhibit satisfying microwave absorption performance. Typically, the copper nanopowder exhibits the RLmin of -23.77dB and the EABmax of 4.64GHz at 1.8mm. This work provides a reference for the application of functional phases in electronic slurry and microwave absorption fields.

Analysis of the Effect of Capacitor Placements at High and Low Voltage Transformer Sides as Voltage Profile and Total Cost in Distribution Systems

This study mentions the problem of determining optimal placements and sizes for capacitor banks by comparing different schemes that allow implemented buses at both high and low voltage side, only high voltage side or low voltage side of transformers in distribution systems. Criterions evaluated for each scheme are active and reactive power losses in whole system, voltage value at all buses, installation and operation cost and accumulative profit saving. Standard with and without transformer branches in distribution systems and Newton-Raphson method are introduced to make clear about the way to analyze power flows in whole system. Optimal placements and sizes for capacitor banks are determined by using a proposed algorithm and optimal capacitor placement tool in ETAP software. Simulation results can help to show the comparisons, evaluations and make decision about optimal capacitor placements and sizes. The contribution shows the best scheme that install capacitors at low voltage side of transformers because it has the lowest implemented capacity, highest economic factors while voltage quality is always in allowable range. Achieved results can be applied in any distribution system, help managers have overall review and decide optimal placements and sizes for capacitor banks. Keywords: Capacitor bank, OCP Tool, ETAP software, Optimal placement, Optimal size, Voltage quality, Optimal cost.

Dielectric response of vegetable oil-based nanofluid and impregnated Kraft paper for high voltage transformer insulation

Methyl ester from vegetable oil has been considered a potential replacement for mineral oil used for power transformer cooling and insulating applications. However, some pertinent properties in making this liquid a better transformer oil based on the laydown standards need to be enhanced to maximize the use of this insulating liquid. Technology involving nano-modification can enhance the properties of these ester liquids placing them in a better position as a good alternative. In this study, we aim to investigate the performance of methyl ester liquid from neem seed oil, a non-food grade oil, when modified with SiO2 insulating nanoparticles at several concentrations. Furthermore, Kraft paper compatibility has also been analyzed to observe their compatibility after impregnation. The breakdown strength, temperature-dependent dissipation loss factor, dielectric constant, and viscosity of both pure and nanofluid samples of neem ester liquid have been measured per standard methods. The nanofluid's dielectric performance has been significantly enhanced by the presence of SiO2 nanoparticles according to results obtained from the experiment. For instance, the dielectric dissipation factor at an operating frequency of 60 Hz has been improved by 96%, 89%, and 79% at 30 °C, 50 °C, and 70 °C respectively relative to the base neem liquid. This remarkable improvement has been attributed to the SiO2 nanoparticle's ability to polarize, trap, and de-trap mobile electrons develop in nanofluid when an electric field is applied.

Design a microwave transmitter using magnetron and two layers waveguides

A magnetron is a power oscillator device used in several radar transmitters for generating the electromagnetic wave (EMW) with a constructive and fixed frequency. In this work, a radar transmitter has been carried out using magnetron operates at 2,458 MHz and two conducting layers waveguides to achieve minimum loss of the signal due to the increased temperature. The magnetron is connected with the high voltage capacitor (1.0 μF) in order to store the alternating current (AC) signal delivered from the high voltage transformer. A waveguide parts have been used as transmission lines in view of connecting the magnetron to the antenna. These parts include two metal layers, the upper layer (outer) is advanced audio coding (AAC) 1350 aluminum conductor and the lower (inner) is copper. The waveguide dimension should be suitable to flow frequency from 2.2 GHz to 3.3 GHz. To measure the operating frequency, a waveguide adapter and a coaxial cable which combined with n-female connector have been connected to magnetron. The wave is delivering to the frequency counter by Bayonet Neill–Concelman (BNC) to n-female connectors. The promising results of the proposed work have been achieved with a maximum power, efficient return loss, acceptable voltage standing wave ratio (VSWR) and low-cost manufacturing.

Development of a Self-Coupling High-Voltage Square Waveform Pulse Transformer

Development of a Self-Coupling High-Voltage Square Waveform Pulse Transformer

GMD impacts on Hydro-Québec system

Geomagnetic disturbances (GMD) affect power systems by causing transformer saturation. The primary impacts of transformer saturation are increased harmonic current injections and var losses, which may lead to damage of high-voltage transformers and/or voltage collapse. The investigation of GMD risks and mitigation strategies requires accurate modeling of a GMD. This paper firstly presents the requirements in terms of modeling components to correctly simulate GMD in EMTP, and secondly the impacts of GMD on Hydro-Québec transmission system, which is fully represented in EMTP, a GMD-EMT simulation world premiere.

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.

Investigation of the dielectric properties and mechanical stability of lignocellulosic biomass based electrical insulation material for high voltage applications

The laminated insulation pressboards are used in electrical transformers and they are made from pure wood cellulose fibre. It is used in high-voltage transformers for electrical insulation due to its superior electrical and mechanical properties. Many researchers are searching for alternatives to wood raw materials to reduce deforestation. The banana is one of the lignocellulose-based raw materials; the banana fibre contains 48% cellulose. In this work, different frequencies and temperatures are used to investigate the electrical characteristics of epoxy resin composites reinforced with banana leaf fibres, including their dielectric constant, dissipation factor, and loss factor. At frequencies ranging from 1 to 10 kHz and temperatures ranging from 30 to 150 °C, the dielectric properties of several composites containing banana leaf fibre are studied. The composite’s dielectric properties gradually increased with temperature and decreased with frequency. Correspondingly, the mechanical tests involving a banana leaf fibre epoxy composite are conducted for tensile, bending, impact, and water absorption. The banana leaf fibre has been treated with a 5% sodium hydroxide (NaOH) solution to increase its dielectric and mechanical strength. According to this study, the mechanical strength of biocomposites containing up to 60% treated banana leaf fibre epoxy (TBLFE) composites is greater than that of pure epoxy. A thermogravimetric investigation of composites reinforced with banana fibres has revealed remarkable thermal stability up to 220 °C. In a composite made from chemically treated banana fibre pressboard, there is a good bond between the fibres and the matrix. The FESEM surface analysis shows that treated banana leaf fibril insulation boards have a better texture than composites that have not been treated. The testing results depict that banana leaf fibre is one of the good alternatives to wood cellulose for electrical insulation on pressboard for high-voltage applications.

Research on suppression effectiveness of compressed air foam for oil-immersed transformer hot oil fire

Transformers, being the largest oil-bearing equipment, are susceptible to high-temperature hot oil fires and large-area flowing fires that can be challenging to extinguish. To investigate the effectiveness of compressed air foams (CAFs) agents in extinguishing fires in ultra-high voltage (UHV) converter transformers, this work examines the fire suppression capabilities of three typical CAFs agents. A test model of a hot oil fire in a transformer with a burning area of 1 m2 was constructed for this purpose. The fire test was conducted by heating the transformer oil using an electric heating system, and the test process was monitored using an unmanned aerial vehicle. The results indicate that three CAFs agents used in the tests are capable of extinguishing a 1 m2 transformer hot oil fire without causing boiling over phenomenon. 1% MJBP CAFs is the fastest with a fire extinguishing time of 168 s, and is even more efficient when the gas to liquid ratio is 9:1. CAFs have the advantage of uniformity and stability, making it suitable for extinguishing hot oil fires in extra high voltage transformers as it does not cause boiling fires during firefighting.