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High voltage power capacitors employ the oil-impregnated polypropylene film as the insulation. The swelling phenomenon might drive the antioxidants and small molecules within the film to migrate into the oil. It is necessary to comprehensively investigate the physical migration mechanism of antioxidants and their impact on the electrical performance of the oil-film combination insulation system and, consequently, formulate the proper selective prescription of antioxidants. Theoretical elucidation of the competitive interaction mechanism between the film and the oil in attracting antioxidant molecules was achieved through the calculation of inter-molecular binding energy, and the migration coefficient ηm was introduced to quantify the migration characteristics of antioxidants. Experimentally, the effects of antioxidants on the space charge distribution of the film, the dielectric properties of the oil, and the breakdown characteristics of both the film and oil were investigated. The experimental conclusions are consistent with theoretical analysis. The lamellar structure antioxidant molecules with ηm > 1 tend to migrate from the film to the oil, which results in increased dielectric loss and decreased breakdown strength of the insulating oil. In addition, the presence of phosphorus atoms in phosphite antioxidants contributes to a reduction in the breakdown strength of the film. For capacitor grade polypropylene film, in addition to the synergistic effect between different types of antioxidants on the thermo-oxidative stability, the structure of the antioxidant molecules and its influence on the electrical performance of the oil–film systems should also be taken into account. [ABSTRACT FROM AUTHOR]

Fly ash cenospheres serve as an inexpensive filler for various composites. Coating their surface with metal significantly alters the properties of the resulting composites. In this study, aluminosilicate cenospheres receive a copper coating using a plasma method with magnetron sputtering. Based on these copper-coated cenospheres, composites are created, and their dielectric properties are investigated in a parallel plate capacitor cell under isotropic pressures ranging from 1 to 75 atm. Composites based on pure fly ash cenospheres exhibit pressure-invariant properties, including the dielectric constant and loss factor. However, for composites based on copper-coated fly ash cenospheres, an abrupt increase in electrical conductivity is observed as the pressure increases. Interestingly, significant changes in electrodynamics characteristics are not detected under the influence of anisotropic stress. The methodology tested in this work can be utilized for creating smart materials based on cenospheres. [ABSTRACT FROM AUTHOR]

This research aims to analyze the implementation of a fuzzy logic-based approach in improving the diagnosis of power transformer oil deterioration, which is critical for maintaining the efficient performance and operational life of transformers. Traditional diagnoses are based on strict measurements that do not account for the factors of variability and uncertainty of the actual data. In this article, we perform six different types of tests in this regard, and data have been collected during the period of 2021 to 2022 of 188 power transformer failures in the New KotLakhpat Lahore unit, whose voltage range is 132/66 kv and rating capacity is 40/50 MVA. In this case, a fuzzy logic-based scheme is developed based upon the membership function, a rule-based and defuzzification method that works with imprecision and the implementation of uncertainty in assessing the condition of transformer oils. Moisture, acidity, and a dissolved gas analysis indicator, along with other indication approaches such as interfacial tension, viscosity, and tangent delta measurement, are used to analyze the deterioration process in transformer oils. In the visual representation, oil samples with the following properties were first fuzzified: 19.9 mm2/s of viscosity, 0.453 mgKOH/g of acidity, 695 ppm of DGA, 20.8 mg/kg of moisture, 19.98 of IFT, and 4.35 × 100.14 of tangent delta. The output that was generated by software using the values entered into the parameters (HI and Age) after defuzzification is 45. Fuzzy logic serves as a concrete framework for transforming the diagnostics system and deterring the threats to the entire transformer's health and reliability in the future. By using this technique, various faults were hypothetically and practically analyzed in a transformer to implement early detection technologies with the possibility to reduce maintenance costs and extend operational life up to 45 years. Various case studies indicate the effectiveness of fuzzy logic in comparison to traditional diagnostics. [ABSTRACT FROM AUTHOR]

Characterized by its exceptional electrical, physical, and chemical properties, 1-phenyl-1-xylylethane (PXE) insulating oil finds extensive application in the realm of power capacitor insulation. In this study, molecular simulation is employed to investigate the reactivity of PXE insulating oil molecules and the impact of temperature on water diffusion behavior in PXE insulating oil, as well as its solubility. The findings demonstrate a higher propensity for hydrogen atoms in nucleophilic and electrophilic positions within PXE insulating oil molecules to interact with water molecules. The inclusion of a temperature field enhances the Brownian motion of water molecules and improves their diffusion ability within the oil. Furthermore, the temperature field diminishes the interaction force between water molecules and the oil medium. Under the influence of this temperature field, there is an increase in the free volume fraction of PXE insulating oil, leading to a weakening effect on hydrogen bonds between oxygen and hydrogen atoms within PXE insulating oil. Additionally, with increasing temperature, there is an elevation in moisture solubility within insulating oil, resulting in a transition from a suspended state to a dissolved state. [ABSTRACT FROM AUTHOR]

The search for alternative, more environmentally friendly coolants to replace mineral oils in power transformers represents a relevant challenge for the power industry. In this frame, a CFD analysis is carried out by means of an open-source, conjugate heat transfer Finite Volume solver to assess the heat transfer performance of different coolants in a disc-type winding of an oil-immersed power transformer, whose geometry is taken from a reference case in the literature. Four different oils are considered: two mineral oils widely established among power transformer manufacturers, a synthetic ester and a natural ester. The latter two represent environmentally friendly alternatives to mineral oils, of great interest for the specific sector. The influence of temperature-dependent thermophysical properties on the overall flow and on the location and value of the hot spots in the copper conductors is discussed, highlighting the strength and weaknesses of the four oils as transformer coolants. In particular, the natural ester exhibits the best heat transfer performance, whereas high hot-spot temperatures and strong fluctuations are found for both mineral oils and the synthetic ester. [ABSTRACT FROM AUTHOR]

This paper proposes a novel fault diagnosis methodology for oil-immersed transformers to improve the diagnostic accuracy influenced by gas components in power transformer oil. Firstly, the Random Forest (RF) algorithm is utilized to evaluate and filter the raw data features, solving the problem of determining significant features in the dataset. Secondly, a multi-strategy Improved Particle Swarm Optimization (IPSO) is applied to optimize a double-hidden layer backpropagation neural network (BPNN), which overcomes the challenge of determining hyperparameters in the model. Four enhancement strategies, including SPM chaos mapping based on opposition-based learning, adaptive weight, spiral flight search, and crisscross strategies, are introduced based on traditional Particle Swarm Optimization (PSO) to enhance the model's optimization capabilities. Lastly, AdaBoost is integrated to fortify the resilience of the IPSO-BP network. Ablation experiments demonstrate an enhanced convergence rate and model accuracy of IPSO. Case analysis using Dissolved Gas Analysis (DGA) samples compares the proposed IPSO–BP–AdaBoost model with other swarm intelligence optimization algorithms integrated with BPNN. The experimental findings highlight the superior diagnostic accuracy and classification performance of the IPSO–BP–AdaBoost model. [ABSTRACT FROM AUTHOR]

Liquid jet fire was one of the typical fires that endangered industrial safety. Especially, the oil-filled equipment of the substation was subjected to an external thermal load, which caused liquid jet fire. However, less literature was available for the formation mechanism of liquid jet flame. Thus, this paper conducted a systematic experiment to reveal the formation mechanism of transformer oil jet fire with various heat release rates (33 kW, 73 kW, 132 kW, and 212 kW). In this paper, the formation mechanism of transformer oil jet fire was clarified. Experimental observation showed that the formation process of transformer oil jet fire can be divided into three stages. The gas–liquid two-phase flow occurred during the formation of transformer oil jet fire. The correlation between the overpressure peak and the heat release rate was established. The medium thermal response behavior can be divided into three stages. When the medium temperature reached the boiling point, the jet fire appeared. The thermal stratification model of a transformer oil jet was established. The correlation between the degree of liquid stratification and dimensionless heat release rate was established. The thermal convection and radiation determined the heat transfer mechanism of oil during the formation of jet fire. [ABSTRACT FROM AUTHOR]

The advances in the field of nanotechnology tends to improve the rate of heat extraction and transmission from foreseeable causes and has fascinated researchers and scientists. Furthermore, nanofluids are having a useful impact on various fields such as nuclear industries, powered lasers, chilling of microelectronic devices, solar energy capture, transformers oil cooling, and in cancer diagnosis. Hence, magnetohydrodynamic (MHD) three-dimensional bioconvective flow of nanofluid accommodating gyrotactic microorganisms over a wedge surface with zero nanoparticles mass flux boundary conditions is studied, using large Reynolds number approximation. The additional novelty of the study is the implementation of the revised Buongiorno model, which deliberates the effects of thermo-migration and Brownian diffusion of nanoparticles, together with passive control of nanoparticles fraction on the wedge surface. The self-similar form of conservation equations of energy, nanoparticle fraction, gyrotactic microorganisms, and momentum are handled numerically. T The results of the Blasius and the Hiemenz flows are retrieved as special cases of the model. It was found that the temperature of the nanofluid increases considerably when considering the nonlinear thermal radiation compared to the linear radiant heat. Increasing the strength of the Brownian diffusion increases the heat transport but reduces the mass transport. [ABSTRACT FROM AUTHOR]

Superalloys, specifically Inconel 617 (IN617), have distinctive properties, yet it is extremely hard to machine through traditional processes. Electric discharge machining (EDM) has been considered a viable option considering the characteristics and shape intricacy required in the applications of the said alloy. However, EDM's low material removal rate (MRR) impedes its use. Therefore, the machining performance of five different transformer oil (TO) based modified dielectrics and cryogenically treated (CT) tools have been thoroughly investigated herein, which has never been examined so far. A total of 30 experiments were executed employing a full factorial design considering three kinds of electrodes and five different modified dielectrics. CT Cu (CuCT) electrode has given the highest magnitude of MRR (19.65 mm3/min) in the blend of tween 80 and TO, and minimum surface roughness (Rz) 11.0 µm in pure TO. The maximum MRR obtained with the CT electrode is 28% greater in comparison to that recorded for non-treated (NT) electrodes. Among the different electrodes, the CuCT tool performed well in TO-based dielectrics by giving the high MRR compared to the other NT and CT electrodes. CT electrodes yield higher MRR in TO-based dielectrics than kerosene oil (KO) based ones. The highest value of MRR noticed with TO-based dielectric is 20.3% than the maximum MRR noted for the KO-based dielectric. A significant amount of improvement in the MRR (98.56%) and Rz (78.88%) has been observed when the mono-objective optimization is utilized to obtain the optimal set of input variables. Finally, an artificial neural network (ANN) has been modelled to accurately forecast the MRR and Rz value for various input conditions, obviating the necessity for tests, effectively modelling the complicated and nonlinear phenomenon of MRR and Rz. [ABSTRACT FROM AUTHOR]

The study determines the frequency–temperature dependence of the conductivity of a moist solid insulation component of power transformers, impregnated with the innovative bio-oil NYTRO® BIO 300X, manufactured from plant-based raw materials. The research was conducted for six moisture levels ranging from 0.6% to 5% by weight, within a frequency range from 10−4 Hz to 5 · 103 Hz and measurement temperatures from 20 °C to 70 °C, with a 10 °C step. The conduction model for both DC and AC, based on the quantum mechanical phenomenon of electron tunneling between water nanodroplets, was used to analyze the obtained results. It was determined that the frequency dependence of the conductivity of pressboard-bio-oil-moisture composites is influenced by two factors as follows: the activation energy of conductivity and the activation energy of relaxation time. For each moisture content, 16 values of the activation energy of the relaxation time and 16 values of the activation energy of conductivity were determined. It was found that the values of activation energy of conductivity and relaxation time are equal and independent of moisture content, frequency, and temperature. Based on 192 residual activation energy values, the mean generalized activation energy value for the relaxation time and conductivity was calculated with high precision, resulting in ΔE ≈ (1.02627 ± 0.01606) eV. The uncertainty of its determination was only ±1.6%. This indicates that electron tunneling from the first nanodroplet to the second, causing AC conductivity, and their return from the second nanodroplet to the first, determining the relaxation time, occur between the same energy states belonging to the water nanodroplets located in the pressboard impregnated with bio-oil. For each moisture content, the curves obtained for different measurement temperatures were recalculated to a reference temperature of 20 °C using the generalized activation energy. It was found that the shifted curves obtained for different temperatures perfectly overlap. Increased moisture content shifts the recalculated curves toward higher conductivity values. It was established that for all moisture contents in the lowest frequency range, conductivity is constant (DC conductivity). A further increase in frequency causes a rapid rise in conductivity. The increasing period can be divided into two stages. The first stage occurs up to about 100 Hz–101 Hz, depending on the moisture content. In the second stage, the rate of conductivity increase is higher, and its value depends on moisture content. The lower the moisture content, the faster the conductivity increases. Recalculation using the generalized activation energy eliminated the effect of temperature on the curves. It was found that the shapes of the recalculated curves and their position relative to the coordinates depend only on the moisture content in the composite. The equality of the activation energy of the relaxation time and conductivity established in the study, as well as their independence from frequency and moisture content in the pressboard impregnated with NYTRO® BIO 300X bio-oil, allows for recalculating the curves of electrical parameters determined at any operating temperatures of the transformer to a reference temperature, for example, 20 °C. Comparing the curve obtained for the transformer, recalculated to the reference temperature, with reference curves determined by us in the laboratory for different moisture contents, will allow for the precise determination of the moisture content of the solid insulation component impregnated with NYTRO® BIO 300X bio-oil. This will contribute to the early detection of approaching critical moisture content, threatening catastrophic transformer failure. [ABSTRACT FROM AUTHOR]

The paper presents experimental findings on the atomization characteristics of coal–water slurries with and without petrochemicals. The fuels were based on flame coal filter cake (slime), which is a typical coal processing waste, flame coal of different particle sizes, wood biomass (sawdust), used transformer oil, and water. The atomized flow characteristics—droplet size and velocity as well as jet angle—were found to depend on the atomizer dimensions and slurry rheology. The experimental data were used to calculate the slurry atomization efficiency factor. The findings were generalized to provide a mathematical description of how the slurry composition and atomizer geometry affect the slurry atomization behavior. Approximations were obtained for atomization characteristics that can be used to predict the jet angle as well as droplet radii and velocities. The developed mathematical tool can be employed to calculate the spraying characteristics when using devices like external-mix twin-fluid atomizers. The approach proposed for data generalization can be applied to adapt the set of approximation equations to other types of nozzles. [ABSTRACT FROM AUTHOR]

The operational stability of the power transformer is essential for maintaining the symmetry, balance, and security of power systems. Once the power transformer fails, it will lead to heightened instability within grid operations. Accurate prediction of oil temperature is crucial for efficient transformer operation. To address challenges such as the difficulty in selecting model hyperparameters and incomplete consideration of temporal information in transformer oil temperature prediction, a novel model is constructed based on the improved whale optimization algorithm (IWOA) and long short-term memory (LSTM) neural network with self-attention (SA) mechanism. To incorporate holistic and local information, the SA is integrated with the LSTM model. Furthermore, the IWOA is employed in the optimization of the hyper-parameters for the LSTM-SA model. The standard IWOA is improved by incorporating adaptive parameters, thresholds, and a Latin hypercube sampling initialization strategy. The proposed method was applied and tested using real operational data from two transformers within a practical power grid. The results of the single-step prediction experiments demonstrate that the proposed method significantly improves the accuracy of oil temperature prediction for power transformers, with enhancements ranging from 1.06% to 18.85% compared to benchmark models. Additionally, the proposed model performs effectively across various prediction steps, consistently outperforming benchmark models. [ABSTRACT FROM AUTHOR]

Defining the copper-based catalysts that are responsible for the catalytic behaviour of oil-paper insulation systems and implementing effective regulation are of great significance. Accelerated ageing experiments were conducted to reveal variations in copper scales and deterioration in insulation properties. As ageing progressed, TEM images demonstrated that copper species were adsorbed and aggregated on the fibre surface in the form of nanoparticles (NPs). The scale of NPs exhibited a continuous increase, from 27.06 nm to 94.19 nm. Cu(I) and Cu(II) species were identified as the active sites for inducing intense free radical reactions, which significantly reduced the activation energy, making the insulating oil more susceptible to oxidation. The role of the antioxidant di-tert-butyl-p-cresol (DBPC) in extending the insulation life was regulated by determining the optimal addition time based on variations in the interfacial tension. After the second addition of DBPC, the ageing rates of the dissipation factor, acidity, micro-water and breakdown voltage in the Cu+DBPC group decreased by 28.8%, 43.2%, 52.9% and 46.7%, respectively, compared to the Cu group. This finding not only demonstrates the crucial role of DBPC in preventing the copper-based catalyst-induced oxidation of insulating oil, but also furnishes a vital foundation for enhancing the long-term stability of transformer insulation systems. [ABSTRACT FROM AUTHOR]

When a transformer is in a long-term heavy load operation state, the oil temperature reaches the alarm temperature; if a slight fault occurs inside the transformer, traditional inverse time current protection and other protections that react to phase current may not operate due to insufficient sensitivity or they may operate for too long. Based on this, this article proposes a new principle of accelerating inverse time overcurrent protection based on transformer oil temperature. The proposed method uses transformer oil temperature to accelerate the action time of traditional inverse-time overcurrent protection, then introduces the transformer oil temperature factor and acceleration index to optimize the inverse time characteristic curve, and establishes a mathematical model to optimize the adjustment for the complexity of adjustment of the protection action equation and the risk of mismatch of the protection after the acceleration of oil temperature. The existing theoretical analysis and simulation verification results show that the proposed new overcurrent protection scheme based on the transformer oil temperature acceleration inverse time can effectively improve the protection of the rapidity and sensitivity, providing a new research idea for the combination of non-electrical and electrical quantity protection. [ABSTRACT FROM AUTHOR]

Hydraulically amplified self‐healing electrostatic (HASEL) actuators generally consisting of dielectric elastomer (DE) and transformer oil have garnered interest in the realm of soft actuators. However, existing DE can hardly reconcile contradictions between high dielectric constants and low modulus, while traditional transformer oil demands a continuous power supply to sustain strain. Herein, by incorporating liquid metal (LM) featuring high dielectric constant and low modulus, with poly(ε‐caprolactone) (PCL) bearing low phase change temperature, a new concept of electric‐thermal dual‐responsive HASEL actuator is first proposed for solid–liquid bi‐stabilized smart switching. It is not only able to simultaneously deliver a tripled dielectric constant of DE from 3.1 to 9.7 (at 1 kHz) and a low modulus (0.12–0.15 MPa), thus achieving a strain of 9% and a specific power of 64.8 W kg−1; but also, PCL replaces the transformer oil, acting as a “temperature switch” for the HASEL actuator, i.e., when PCL solidifies, the HASEL actuator stabilizes the deformation, allowing it to continue working even without power supply. Exemplified by valve, the as‐prepared dual‐responsive HASEL actuator can independently control the flow rate of each valve unit. This electric‐thermal dual‐responsive HASEL actuator introduces an innovative strategy for developing the next generation of multifunctional smart switching. [ABSTRACT FROM AUTHOR]

In recent days, ester-based alternatives like natural and synthetic oils are preferred as an alternative to mineral oil by the power industry due to its higher bio-degradability, superior thermal conductivity, and fire resistance than mineral oil. In addition to this, blended oils are quite attractive because of its low dielectric loss and a low ratio of degradation. The present research deals with the experimental studies on different insulating oils like mineral oil, synthetic ester oil, coconut oil, blended oils, and nanofluids, which are developed from ZnO and TiO2 nanoparticle doped at 0.01 vol% in different insulating oils through ultrasonication process. In this experiment, the critical properties like electrical and physicochemical properties are examined according to International Electrotechnical Commission and American Society for Testing and Materials standards. Results show that ZnO and TiO2 nano-powder enhances the AC breakdown voltage (BDV), dielectric permittivity, and DC resistivity properties of different insulating oils with improved flash and fire resistance. Remarkably, it is found that mineral oil-based TiO2 nanofluid shows an enhancement of 55.8 % in AC BDV, 9.1 % in permittivity, and 15 % in flash resistance. Moreover, mineral oil based ZnO and TiO2 nanofluid results exhibit remarkable decrement in loss tangent with increased DC resistance property. Finally, it is observed that the influence of TiO2 nano-powder at 0.01 vol% remarkably enhances the electrical and physicochemical properties in different insulating oils compared to ZnO nanofluids. Hence, mineral oil and green insulating based synthetic ester oil (which is based on TiO2 nanofluids) have been considered as a potential candidate to make alternatives to traditional insulating oil for power transformer applications. The findings offer critical insights for the future of transformer insulation systems, guiding industry standards and fostering innovation in material science. [ABSTRACT FROM AUTHOR]

This paper presents the experimental findings on the effects of antioxidants on the corrosion of copper strips immersed in mineral oil (MO)-antioxidant samples. First, the uninhibited MO was mixed thoroughly with dibenzyl disulphide (DBDS) or 2,6-di-tert-butyl-p-cresol (DBPC) at different concentrations (5, 15, 25, 50, and 200 mg/kg) using a hot plate magnetic stirrer set at a temperature of 73 °C and stirring speed of 750 rpm for 15 min. Following this, the MO-antioxidant samples were poured into separate test vessels and copper strips were added into the vessels. Next, each MO-antioxidant sample was blanketed with nitrogen gas, sealed, and placed in a forced convection laboratory oven. The MO-antioxidant samples were then thermally aged at 150 °C for 48 h. The results showed that the acidity of the MO-antioxidant sample decreased with an increase in the antioxidant concentration, regardless whether the antioxidant was DBDS or DBPC. However, the corrosion of the copper strip worsened with an increase in the antioxidant concentration, where DBDS had a higher relative degree of corrositivity to copper compared with DBPC. In addition, the results showed that a DBPC concentration of 25 mg/kg reduced the the acidity of the MO-antioxidant sample and resulted in a moderate tarnish of the copper strip. [ABSTRACT FROM AUTHOR]

Despite the fact that doping nanoparticles into insulating transformer oil has proven to be an effective method of enhancing its dielectric and electrical properties, it remains unclear how different types and surface conditions of nanoparticles may affect their dielectric and electrical properties. Therefore, the effect of doping various types of BN nanoparticles (nanosphere, nanotube, and nanosheet) in insulating mineral oil (MO) on the diffusion properties of water molecules and electrical properties across the BN/MO interface was investigated using molecular dynamics (MD) and Density Functional Theory (DFT) simulations. Our results show that different surface morphology and grafted functional groups in different types of BN nanoparticles have a significant impact both on the water diffusion behavior and the interfacial potential barrier across the interface between BN and MO. In the MO system directly doped by BN nanospheres, water diffusion behavior is not significantly restricted. However, grafting -NH2 polar groups onto the BN nanoparticle surface may significantly limit the diffusion behavior of water due to the strong attraction between the -NH2 polar groups and water molecules; the most significant effect is with nanospheres, followed by nanotubes and nanosheets. In terms of electrical properties across the interface between BN and MO, the h-BN surface (derived from BN nanosheets and nanotubes) acts as a trap for electrons in MO (−0.59 eV), while the c-BN surface (derived from BN nanospheres) acts as a potential barrier for electrons in MO (1.45 eV), and it is noteworthy that the presence of water molecules near the interface between BN and MO has little impact on the potential barriers. Advancing a fundamental understanding of the electrical and water diffusion properties of MO in correlation with the surface morphology of different types of nanoparticles is key to improving the insulation properties of oil-impregnated power transformers. [ABSTRACT FROM AUTHOR]

Using first-principles theory, this work purposes Ru-doped Janus WSSe (Ru-WSSe) monolayer as a potential gas sensor for detection of three typical gas species (CO, C2H2, and C2H4), in order to evaluate the operation status of the oil-immersed transformers. The Ru-doping behavior on the WSSe surface is analyzed, giving rise to the preferred doping site by the replacement of a Se atom with the formation energy of 0.01 eV. The gas adsorption of three gas species onto the Ru-WSSe monolayer is conducted, and chemisorption is identified for all three gas systems with the adsorption energy following the order: CO (−2.22 eV) > C2H2 (−2.01 eV) > C2H4 (−1.70 eV). Also, the modulated electronic properties and the frontier molecular orbital are investigated to uncover the sensing mechanism of Ru-WSSe monolayer upon three typical gases. Results reveal that the sensing responses of the Ru-WSSe monolayer, based on the variation of energy gap, to CO, C2H2, and C2H4 molecules are calculated to be 1.67 × 106, 2.10 × 105, and 9.61 × 103, respectively. Finally, the impact of the existence of O2 molecule for gas adsorption and sensing is also analyzed to uncover the potential of Ru-WSSe monolayer for practical application in the air atmosphere. The obtained high electrical responses manifest strong potential as a resistive sensor for detection of three gases. The findings hold practical implications for the development of novel gas sensing materials based on Janus WSSe monolayer. We anticipate that our results will inspire further research in this domain, particularly for applications in electrical engineering where the reliable detection of fault gases is paramount for maintaining the integrity and safety of power systems. [ABSTRACT FROM AUTHOR]

The widespread prevalence of polychlorinated biphenyls (PCBs) in the environment has raised major concerns due to the associated risks to human health, wildlife, and ecological systems. Here, we investigated the degradation kinetics, Bayesian network (BN), quantitative structure–activity relationship-density functional theory (QSAR-DFT), artificial neural network (ANN), molecular docking (MD), and molecular dynamics stimulation (MS) of PCB biodegradation, i.e., PCB-10, PCB-28, PCB-52, PCB-138, PCB-153, and PCB-180 in the soil system using fungi isolated from the transformer oil–contaminated sites. Results revealed that the efficacy of PCB biodegradation best fits the first-order kinetics (R2 ≥ 0.93). The consortium treatment (29.44–74.49%) exhibited more efficient degradation of PCBs than those of Aspergillus tamarii sp. MN69 (27.09–71.25%), Corynespora cassiicola sp. MN69 (23.76–57.37%), and Corynespora cassiicola sp. MN70 (23.09–54.98%). 3′-Methoxy-2, 4, 4′-trichloro-biphenyl as an intermediate derivative was detected in the fungal consortium treatment. The BN analysis predicted that the biodegradation efficiency of PCBs ranged from 11.6 to 72.9%. The ANN approach showed the importance of chemical descriptors in decreasing order, i.e., LUMO > MW > IP > polarity no. > no. of chlorine > Wiener index > Zagreb index > HOMU > Pogliani index > APE in PCB removal. Furthermore, the QSAR-DFT model between the chemical descriptors and rate constant (log K) exhibited a high fit and good robustness of R2 = 99.12% in predicting ability. The MD and MS analyses showed the lowest binding energy through normal mode analysis (NMA), implying stability in the interactions of the docked complexes. These findings provide crucial insights for devising strategies focused on natural attenuation, holding substantial potential for mitigating PCB contamination within the environment. [ABSTRACT FROM AUTHOR]

Electric Power Research Institute of Guangdong Power Grid Co., Ltd., Guangzhou, China, 2Guangdong Power Grid Co., Ltd., Guangzhou, China, 3China Southern Power Grid Co., Ltd., Guangzhou, China To achieve load management optimization and timely failure warning for power transformers, as well as improve the reliability of the power network, this paper proposes a multiple time scale prediction method for top oil temperature (TOT) based on an adaptive extended Kalman filter (AEKF) algorithm. This method combines the Kalman filter (KF) algorithm and the D. Susa thermal model. The TOT, oil exponent and oil time constant are taken as state variables, while the ambient temperature and load current are used as input variables. The iterative optimization of the oil exponent and oil time constant is realized by comparing the estimated and observed TOT values. Moreover, the proposed method utilizes an adaptive noise estimator to correct the noise statistics parameters, which simplifies the initial noise setting and thus further improves the TOT prediction accuracy. A case study is conducted with two 110 kV transformers. The results show that comparing the thermal equivalent circuit model and the extended KF algorithm, the proposed method has a higher accuracy in the intraday ultra-short-term prediction on a 15-min time scale and day-ahead short-term prediction on a 24-h time scale for the TOT. [ABSTRACT FROM AUTHOR]

In order to solve the problem of remote oil level measurement for unmanned transformers, this paper proposes an online monitoring technology for transformer oil level based on ultrasonic sensors. Subsequently, a finite element model and experimental testing platform were constructed to analyse and verify the influencing factors of the transformer oil level sensors. The results indicated that there is a lower measurement error at 140 kHz in the ultrasonic frequency range of 20–320 kHz, which can be selected as the recommended frequency. The impurities in the oil and the thickness of the tank wall have a slight impact on the accuracy of oil level measurement, and can lead to a decrease in the signal‐to‐noise ratio of the echo. Furthermore, as the speed of sound increases by about 4 m/s, for every 1°C increase in oil temperature, it is necessary to calibrate the measurement results based on the oil temperature. The test results of actual experimental transformers showed that the designed online monitoring device can achieve high‐precision monitoring of transformer oil level, with a relative error generally less than 3%. [ABSTRACT FROM AUTHOR]

Transformers are crucial equipment in electrical distribution systems but have a significant potential for failure. Insulation materials, including transformer oil (TO), play a primary role in transformer failures. A fire involving the TO can lead to a large explosion, causing the main tank to rupture and resulting in extensive damage to the entire transformer and the surrounding area. Mineral oil (MO) is the most widely used type due to its availability and relatively low cost compared to other types of oil. However, MO has a critical disadvantage, which is its very low flash point. The low flash point makes MO highly flammable. When the oil fires in an enclosed space, such as a transformer tank, the pressure inside the tank increases, leading to a large explosion. Therefore, research on increasing the flash point of MO is highly necessary. The application of nanotechnology is a promising approach to increasing the flash point of base fluids. Research on the effect of nanoparticles (NPs) on flash points is very limited in the literature; thus, there is significant potential for further research in this field. The majority of studies indicate an increase in flash points with the addition of NPs to MO. There is only one study that shows a decrease in flash point, which is −1.33% compared to MO. From all the reviewed studies, it can be concluded that NPs are a potential solution to increase the flash point of MO. Despite their benefits, NPs require a thorough examination of health and environmental impacts, along with proper waste management, to ensure their advantages. [ABSTRACT FROM AUTHOR]

This study investigates the combustion characteristics of KI-25# transformer oil under varying radiation conditions using a cone calorimeter experiment. Parameters such as ignition time, mass loss rate, heat release rate, total heat release, fire performance index, fire growth index, and other relevant factors were analyzed. The aim was to evaluate combustion behavior under different external radiation levels and initial fuel thicknesses. The results indicate that ignition time decreases with increasing external radiation, while the impact of oil thickness on ignition time is minimal but shows an overall upward trend. The mass loss rate exhibits a linear increase with rising radiation flux and initial oil thickness. Additionally, total heat release increases proportionally with oil thickness. Consequently, the fire performance index decreases, and the fire growth index rises, indicating an elevated fire risk index level. This study provides valuable insights for transformer fire safety practices and is crucial for enhancing power system safety. [ABSTRACT FROM AUTHOR]

When using transformer insulation oil as a liquid dielectric, the oil is easily polluted by the solid particles generated in the operation of the transformer, and these metallic impurity particles have a significant impact on the insulation performance inside the power transformer. The force of the metal particles suspended in the flow insulation oil is multidimensional, which will lead to a change in the movement characteristics of the metal particles. Based on this, this study explored the motion rules of suspended metallic impurity particles in mobile insulating oil in different electric field environments and the influencing factors. A multiphysical field model of the solid–liquid two-phase flow of single-particle metallic impurity particles in mobile insulating oil was constructed using the dynamic analysis method, and the particles' motion characteristics in the oil in different electric field environments were simulated. The motion characteristics of metallic impurity particles under conditions of different particle sizes, oil flow velocities, and insulation oil qualities and influencing factors were analyzed to provide theoretical support for the detection of impurity particles in transformer insulation oil and enable accurate estimations of the location of equipment faults. Our results show that there are obvious differences in the trajectory of metallic impurity particles under different electric field distributions. The particles will move towards the region of high field intensity under an electric field, and the metallic impurity particles will not collide with the electrode under an AC field. When the electric field intensity and particle size increase, the trajectory of the metallic impurity particles between electrodes becomes denser, and the number of collisions between particles and electrodes and the motion speed both increase. Under the condition of a higher oil flow velocity, the number of collisions between metal particles and electrodes is reduced, which reduces the possibility of particle agglomeration. When the temperature of the insulation oil changes and the quality deteriorates, its dynamic viscosity changes. With a decrease in the dynamic viscosity of the insulation oil, the movement of the metallic impurity particles between the electrodes becomes denser, the collision times between the particles and electrodes increase, and the maximum motion speed of the particles increases. [ABSTRACT FROM AUTHOR]

Removing polychlorinated biphenyls (PCBs) from subsurface water, soils, and transformer oil is crucial to save the environment from these pollutant materials. Hydrodechlorination (HDC) of PCBs consists of numerous chemical reactions and the simple kinetic models may not provide details for the process. To gain more awareness of the reaction mechanism, in the proposed approach, the isoconversional methods of the Friedman were investigated paralleling other kinetic models of Langmuir‐Hinshelwood (L‐H), Eley‐Rideal (E‐R), pseudo‐first‐order, and pseudo‐second‐order methods. The analysis was validated by laboratory results of HDC of contaminated transformer oil in front of Pd/MWCNTs. The most reactivity was observed for biphenyls with a higher number of chlorines. Finding a suitable model, Akaike Information Criteria were applied. It was attained that Friedman model was the most suitable for monitoring of HDC of PCBs in front of catalyst. Besides, E‐R reaction was appropriate to elucidate the theoretical interpretations of the adsorption and desorption of reactants and chlorinated benzene. [ABSTRACT FROM AUTHOR]

Partial discharge is a fault that occurs at the site of insulation defects within a transformer. Dual instances of partial discharge origination discharging simultaneously embody a more intricate form of discharge, where the interaction between the discharge sources leads to more intricate and unpredictable insulation damage. Conventional piezoelectric transducers are magnetically affixed to the exterior metal tank of transformers. The ultrasonic signals emanating from partial discharge undergo deflection and reverberation upon traversing the windings, insulation paperboards, and the outer shell, resulting in signal attenuation and thus making it difficult to detect such faults. Furthermore, it is challenging to distinguish between simultaneous discharges from dual partial discharge sources and continuous discharges from a single source, often leading to missed detection and repairs of fault points, which increase the maintenance difficulty and cost of power equipment. With the advancement of MEMS (Micro-Electro-Mechanical System) technology, fiber-optic ultrasonic sensors have surfaced as an innovative technique for optically detecting partial discharges. These sensors are distinguished by their minute dimensions, heightened sensitivity, and robust immunity to electromagnetic disturbances. and excellent insulation properties, allowing for internal installation within power equipment for partial discharge monitoring. In this study, we developed an EFPI (Extrinsic Fabry Perot Interferometer) optical fiber ultrasonic sensor that can be installed inside transformers. Based on this sensor array, we also created a partial discharge ultrasonic detection system that estimates the directional information of single and dual partial discharge sources using the received signals from the sensor array. By utilizing the DOA (Direction of Arrival) as a feature recognition parameter, our system can effectively detect both simultaneous discharges from dual partial discharge sources and continuous discharges from a single source within transformer oil tanks, meeting practical application requirements. The detection methodology presented in this paper introduces an original strategy and resolution for pinpointing the types of partial discharges occurring under intricate conditions within power apparatus, effectively distinguishing between discharges from single and dual partial discharge sources. [ABSTRACT FROM AUTHOR]

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The utilization of waste transformer oil (WTO) for combustion applications can offer significant potential to generate thermal energy and reduce industrial waste disposal. This study focuses on the development of a burner system designed to utilize WTO as an alternative fuel blended with 30% biodiesel and 70% diesel (B30) to produce thermal energy for various applications in industrial processes. Moreover, the economic feasibility and performance test were explored to provide an overview of the economically designed burner system and inform that WTO blended with B30 is suitable for an environmentally friendly alternative fuel. The development combustor consists of a vertical metal tube cylinder supplied with pressurized air from a blower. Secondary air flow was also provided at the tip of the burner for complete combustion of the fuel. Various test scenarios were conducted to optimize combustion and emission performance. The combustion temperature of the fuel was measured at the tip of the burner, while the emissions gases were recorded at 150 cm above the burner tip. Based on the experimental results, it is shown that the developed burner system can effectively burn the WTO blended B30 to produce thermal with low emissions gases. The maximum combustion temperature reached by the burner is 979°C, achieved with a combustion mixture consisting of 30%:70% WTO/B30 (v/v). The economic feasibility of the developed burner system was very useful and inexpensive to be developed at household or industrial scales and emissions from the combustion process are relatively low, with no significant environmental or health risks. Future studies may explore different fuel blends, system improvements, and broader industrial applications. [ABSTRACT FROM AUTHOR]

Greenhouse gas CO2 has rarely been used as an insulating gas in cellulose/oil insulated energy devices since the benefits of it on dielectric properties of cellulose/oil have yet to be known. This work reveals that CO2 can be adsorbed by unaged and aged cellulose, improving the breakdown strength of cellulose/oil composite. The traps introduced by CO2 adsorption are proved to be the key factor. The adsorption of CO2 makes shallow traps shallower, while making deep traps deeper. These changes in traps hinder the charge accumulation on dielectric surfaces and enhance the electron capture ability in the dielectric bulk. Moreover, the charge mobility and electrical conductivity of cellulose/oil composite increase after adsorbing CO2, while the surface potential is reduced. Therefore, the collisional ionization is hindered and further electrical breakdown is improved. In the meantime, the energy level distribution models of cellulose–air and cellulose–CO2 composites were comparably studied. This work is conducive to understanding the changes in electrical properties after CO2 adsorption and the prospects of CO2 in cellulose/oil insulation. [ABSTRACT FROM AUTHOR]

Abstract This article deals with the improvement of the dielectric properties of TUK cellulose paper by impregnation. The experiment was carried out using a nanofluid based on vegetable oil esters and iron nanoparticles (FeO3). The insulating liquids used are palm kernel oil methyl ester (PKOME) and castor oil methyl ester (COME). The evaluation of the improvement is based on the analysis of the flashover voltage of the creeping discharges produced on the immersed paper. The tests were carried out under a positive lightning impulse voltage and for two electrode configurations. The concentrations of nanoparticles used in the experiment are 0.10 wt.%, 0.15 wt.% and 0.20 wt.%. The experimental results show that the 0.10 wt.% concentration gives the best improvement for the two electrode configurations used. The improvements are 53% for the inclined tip and 56.90% for the vertical tip in the case of COME + FeO3. For PKOME + FeO3, the results are 59.90% and 64.60%, respectively, for the two configurations.

The transformer mineral oil is generally hydrocarbon-based and is not environmentally friendly, so it holds a significant share in environmental pollution. As an alternative to conventional transformer oil, plant-based insulation oil has been investigated globally in the past few decades. Even though vegetable oils are considered an environmentally viable alternative to mineral oil, the extensive utilization of vegetable oils could create a threat to Indian food security. The present work focuses on using Pongamia Pinnata oil (PPO) as a significant alternative to conventional transformer oil (CTO) in distribution transformers. The effectiveness of the proposed PPO is experimentally verified using thermal studies and electrical studies through a low-level distribution transformer of 1 kVA. A comparative analysis was carried out between the proposed and conventional oil regarding physical, chemical, and thermal properties. Also, scanning electron microscopy (SEM) and Energy Dispersive X-ray spectroscopy analysis have been carried out for fibreglass cloth insulation material with PPO and CTO to ensure the intrinsic structural strength of the insulation material. The structural strength ensures the bonding and life span of the insulation in the transformer. The cost–benefit analysis is also favourable for the proposed oil as a better green liquid dielectric for transformers. [ABSTRACT FROM AUTHOR]

2-Furaldehyde (2-FAL) is one of the main by-products of the degradation of hemicellulose, which is the solid material of the oil–paper insulating system of oil-filled transformers. For this reason, it has been suggested as a marker of the degradation of the insulating system; sensing devices for 2-FAL analysis in a wide concentration range are of high interest in these systems. An optical sensor system is proposed; this consists of a chemical chip, able to capture 2-FAL from the insulating oil, coupled with a surface plasmon resonance (SPR) probe, both realized on multimode plastic optical fibers (POFs). The SPR platform exploits gold nanofilm or, alternatively, a double layer of gold and silicon oxide to modulate the sensor sensitivity. The capturing chip is always based on the same molecularly imprinted polymer (MIP) as a receptor specific for 2-FAL. The system with the SPR probe based on a gold nanolayer had a higher sensitivity and a lower detection limit of fractions of μg L−1. Instead, the SPR probe, based on a double layer (gold and silicon oxide), has a lower sensitivity with a worse detection limit, and it is suitable for the detection of 2-FAL at concentrations of 0.01–1 mg L−1. [ABSTRACT FROM AUTHOR]

The paper presents results of finite element modeling, development of and experiments with the measuring cell based on a symmetric stripline for measuring coarse-grained soil permittivity. The wave impedance of the measuring cell section intended for filling with soil, is about 80 Ω to expand the frequency range. This allows reducing the width of the central strip and increasing the critical frequency, which cause the higher-order modes. Cell sections with the transfer from SMA connectors to measuring section are filled with a solid dielectric. The distance between outer conductors and the central strip width in these sections, are linearly increased to the size of the measuring section to provide the wave impedance of 50 Ω. The wave impedance growth in the measuring section is considered in the soil complex permittivity calculations. The complex permittivity is measured for five calibration liquids with the static permittivity of 2.27 (transformer oil) to 78.5 (water) and three soil samples with different moisture. It is shown that acceptable values of measurement error can be obtained if the real part of the complex permittivity does not exceed 23–25 units at a frequency of ~1 GHz. [ABSTRACT FROM AUTHOR]

Based on the SOS + MCL approach (SOS—generator with output Semiconductor Opening Switch; MCL—Magnetic Compression Line), a high-power solid-state picosecond system has been developed. The SOS generator forms an initial pulse with a power of 8.5 GW (0.65 MV at a load of 50 Ω) and a duration of 7 ns, which is fed to the input of a magnetic compressor containing 4 lines MCL1–MCL4 connected in series. Structurally, each MCL is a coaxial line and contains ferrite rings placed on its inner conductor and magnetized by an external longitudinal magnetic field. The lines are filled with transformer oil at excess pressure. Each line compresses the pulse in time and increases its peak power. At the output of the last line, MCL4, the peak power increases to 100 GW (2.2 MV at 48 Ω load), and its duration decreases to 100 ps. Record high values of rise rates for voltage, current, and power have been achieved. At a 48 Ω load, the voltage rise rate reaches 27 MV/ns, and the power rise rate reaches 2 TW/ns. In a line with an impedance of 7 Ω, a current pulse with an amplitude of 100 kA and a rise rate of 1.18 MA/ns was obtained. It has been established that the duration of the pulse (full width at half maximum) generated in MCLs corresponds to the double transit time of an electromagnetic wave between the electrodes of the line in the transverse direction. Numerical models have been developed to study the operation of MCLs. Using the models, the internal structure of the process of power amplification in the line was studied, and an assessment was made on the influence of the processes of gyromagnetic precession on the operation of the lines. [ABSTRACT FROM AUTHOR]

The possible mechanisms of electrical breakdown of transformer oil at low voltage values at alternating voltage were investigated. The formation of streamers from the surface of bubbles into a liquid dielectric after partial discharge in a bubble was detected. This phenomenon has been observed for bubbles in pure transformer oil, in transformer oil with the addition of carbon nano-tubes, in oil after operation. At very low voltages, streamers in transformer oil were registered if a partial discharge in the bubble was stimulated by X-rays. Three possible mechanisms of electric breakdown of a gap filled with transformer oil were revealed at low values of electric field strength in the range from 13 to 51 kV/cm. The appearance of streamers from bubbles was preceded by deformation of the bubble due to one or more partial discharges in it. Streamers always appeared in pairs from the poles of the bubble except for the case of the transformer oil with carbon nanotubes. The results obtained are important for understanding the mechanisms of breakdown of transformer oil at very low voltage and can explain the causes of a number of accidents in high-voltage installations. [ABSTRACT FROM AUTHOR]

Partial discharge in oil paper insulation is an important reason for insulation breakdown. The study of partial discharge in transformer oil is of great significance for ensuring the reliability of transformers. In this paper, a comprehensive observation platform of partial discharge with needle plate electrode and oil-paper insulation is built, and the original shape image set of partial discharge is collected and established. Through multi-channel convolution processing of the true color image, gray level equivalent distribution of 3D section, segmentation stretching of threshold interval and binary neighborhood search, a general technical method suitable for processing a series of low brightness discharge images with background interference is finally obtained. [ABSTRACT FROM AUTHOR]

Coal is used in most of the power and chemical plants to meet energy needs which produce various waste ashes. Reuse of these ashes as electroactive materials has great importance for sustainable development. In this study, it was detected that the main components of coal fly (CFA) and bottom ashes (CBA) were oxides of silica (SiO2), iron (Fe2O3), aluminium (Al2O3), and magnesium (MgO), besides carbon. These are well-known electrorheological (ER) active materials. The aim of this study is to reveal dielectric and electroactive vibration damping capabilities of CFA and CBA. According to the dielectric and ER flow tests carried out in insulating silicone oil (SO), the optimum concentration of particles was determined to be 35 wt.% for both ashes. Higher ER yield stress (τy = 135 Pa), higher ER efficiency (32.8), and better viscoelastic properties (τc = 128 Pa, G' = 680 kPa) under 3.0 kV mm-1 applied electric field were obtained for 35CFA/SO suspension system compared to 35CBA/SO (τy = 125 Pa, EReff = 24.0, τc = 55 Pa, G' = 260 kPa). Although it was concluded that both ashes can be upcycled to sustainable and smart vibration damping alternative materials, better performance was observed for CFA particles. [ABSTRACT FROM AUTHOR]

Methyl ester is considered one of the alternative substitutes to mineral oil as an insulating liquid. This study investigates the dissolved gas analysis (DGA) of the methyl ester derived from palm oil, under low energy discharge faults. The aims are to understand the gas composition and evaluate the applicability of the well-established fault interpretation methods for mineral oil to the methyl ester. Experimental procedures were conducted based on the International Electrotechnical Commission (IEC) standards. It involved simulating electrical breakdowns in laboratory conditions as per IEC-156 standard and analyzing gas samples using gas chromatography based on IEC-567. Results show that methyl ester oils produce similar types of gases as mineral oils but at higher concentrations. The interpretation of DGA results using fault identification methods such as Duval Triangle, Duval Pentagon, and IEC ratio indicates an overestimation of fault severity in methyl ester oils, and categorizing the faults as high energy discharge. However, the key gas method correctly identifies the discharge in both methyl ester and mineral oils. These findings suggest the need for adjustments in existing DGA methods to account for the higher gas concentrations in methyl ester oils, for effective condition monitoring and maintenance of transformers if it was filled with methyl ester oil. [ABSTRACT FROM AUTHOR]

Copyright of Przegląd Elektrotechniczny is the property of Przeglad Elektrotechniczny and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Techno.com is the property of Universitas Dian Nuswantoro, Fakultas Ilmu Komputer and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Machine Tool & Hydraulics is the property of Guangzhou Mechanical Engineering Research Institute (GMERI) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This study aims to assess the compatibility of various e-thermal fluids for immersion cooling in battery electric vehicles through a copper wire resistance corrosion test. The tested fluids include a polyalphaolefin, diester, mineral oil API G-III, transformer oil, and a fully formulated dielectric coolant. The test was conducted at 130 °C for 336 h, and the resistance of the copper wires was monitored in vapor and oil phases. By comparing the resistance variation and analyzing portions of the wires through scanning electron microscopy, it was found that the vapor phase of PAO and diester in one of the tests exhibited significant corrosion, while the dielectric coolant showed minimal corrosive effects, implying better compatibility. These results provide insights into the corrosion behavior and compatibility of the fluids with copper, which are essential for selecting suitable dielectric fluids for immersion cooling applications in electric vehicles. [ABSTRACT FROM AUTHOR]

Fractional calculus expands the idea of differentiation to fractional/non‐integer orders of the derivatives. It includes the memory‐dependent and non‐local system's behaviors while fractal–fractional derivatives is the generalization of fractional‐order derivatives which refers to a combination of fractional calculus and fractal geometry. In this article, we have considered the magnetohydrodynamic (MHD) flow of Casson hybrid nanofluid through a vertical open channel with the effect of viscous dissipation and Newtonian heating. The problem is modeled in terms of non‐linear and coupled integer‐order PDEs which is further generalized through fractal–fractional derivative of power law kernel. Due to non‐linearity and complexities, we have adopted the numerical procedure as it is used when the analytical solutions of PDEs are frequently difficult or impossible for complicated situations. We have established the numerical algorithms for both the classical and fractal–fractional‐order model and compared the results. The existence and uniqueness of the model's solution has been shown theoretically. The effect of various embedded parameters on the heat transfer and fluid flow has been simulated and presented through various figures while skin friction and Nusselt number are tabulated. The effect of fractional and fractal parameter is also shown. As the present model is taken for the hybrid nanofluid flow and for the heat transfer applications, we have considered mineral transformer oil as a base fluid while titania and cadmium telluride nanoparticles are dispersed in it. From the results, it is observed that hybrid nanofluid have a better heat transfer enhancement up to 19.71% while the unitary nanofluids are only capable to enhance the heat transfer up to 9%. [ABSTRACT FROM AUTHOR]

The power transformer is one of the most crucial pieces of high-voltage equipment in the power system, and its stable operation is crucial to the reliability of power transmission. Partial discharge (PD) is a key factor leading to the degradation and failure of the insulation performance of power transformers. Therefore, online monitoring of partial discharge can not only obtain real-time information on the operating status of the equipment but also effectively predict the remaining service life of the transformer. Meanwhile, accurate localization of partial discharge sources can assist maintenance personnel in developing more precise and efficient maintenance plans, ensuring the stable operation of the power system. Dual partial discharge sources in transformer oil represent a more complex fault type, and piezoelectric transducers installed outside the transformer oil tank often fail to accurately capture such discharge waveforms. Additionally, the sensitivity of the built-in F-P sensors can decrease when installed deep within the oil tank due to the influence of oil pressure on its sensing diaphragm, resulting in an inability to accurately detect dual partial discharge sources in transformer oil. To address the impact of oil pressure on sensor sensitivity and achieve the detection of dual partial discharge sources under high-voltage conditions in transformers, this paper proposes an optical fiber ultrasonic sensor with a pressure-balancing structure. This sensor can adapt to changes in oil pressure environments inside transformers, has strong electromagnetic interference resistance, and can be installed deep within the oil tank to detect dual partial discharge sources. In this study, a dual PD detection system based on this sensor array is developed, employing a cross-positioning algorithm to achieve detection and localization of dual partial discharge sources in transformer oil. When applied to a 35 kV single-phase transformer for dual partial discharge source detection in different regions, the sensor array exhibits good sensitivity under high oil pressure conditions, enabling the detection and localization of dual partial discharge sources in oil and winding interturn without obstruction. For fault regions with obstructions, such as within the oil channel of the transformer winding, the sensor exhibits the capability to detect the discharge waveform stemming from dual partial discharge sources. Overall, the sensor demonstrates good sensitivity and directional clarity, providing effective detection of dual PD sources generated inside transformers. [ABSTRACT FROM AUTHOR]

Predicting the concentration of dissolved gases in transformer oil is a critical activity for the early detection of potential faults. To address the prevalent issue of data leakage in current prediction methods, this paper proposes a prediction method that completely avoids data leakage. First, the Hodrick Prescott (HP) filter is used for stepwise decomposition to obtain the long-term trend and high-frequency periodic component. The high-frequency periodic component is further decomposed using singular spectrum analysis (SSA) to extract periodic features. Dispersion entropy (DE) and fuzzy entropy (FE) are utilized alongside the HP and SSA methods to determine the optimal decomposition windows during the process, enhancing the ability of the model to acquire time series features. Then, variational mode decomposition (VMD) is applied to remove noise from the high-frequency component. Finally, the long short-term memory network (LSTM) is employed to predict each decomposed component, and the network parameters undergo optimization through the sparrow search optimization algorithm (SSOA). The two case studies in this work verify that the proposed model excels over other prediction means, providing strong support for subsequent fault prediction. [ABSTRACT FROM AUTHOR]

Vegetable insulating oil, with advantages such as high safety and environmental friendliness, is a good substitute for traditional mineral oil. However, thermal failure is one of the important factors affecting the safe operation of oil-immersed electrical equipment. This study focuses on soybean vegetable oil as the research subject and establishes a simulation model for soybean insulating oil to investigate the influence of thermal stress at different temperatures ranging from 1000 K to 2000 K on system decomposition and gas generation characteristics. The results indicate that, under elevated temperatures, the decomposition of soybean vegetable insulating oil predominantly occurs through decarboxylation reactions, leading to the generation of CO2 and hydrocarbon radicals. The hydrocarbon radicals further decompose and react with other species, resulting in the formation of characteristic gases. It was observed that CO2 and C2H4 serve as stable thermal decomposition by-products. Increasing temperatures significantly enhance the generation rates of various characteristic products and broaden the variety of such products. For instance, H2 and CH4 are characteristic gases produced at different temperature ranges. Studying the decomposition and gas generation characteristics of vegetable insulating oil under thermal stress holds crucial significance for transformer design and operation. [ABSTRACT FROM AUTHOR]

In the world, the waste of one situation is the perfect requirement for the other situation. The value addition of the waste can produce new products which contribute to different applications. The electrical grid system produced the transformer oil wastes based on their use and capacity. This waste can be converted into useful applications in the CI engine by pyrolysis at 480 °C. This Pyrolysed oil of transformer oil waste (POTOW) is blended with diesel as a 1:3 contribution by volume for improved fuel properties. But it produced lesser performance. Therefore, the nanoparticles of Titanium dioxide and Silicon dioxide are added to the blend to generate the nano fuel. Enhanced performance and emission reduction are tried with 2–6 lpm hydrogen induction with the nano fuel in a 5.2 kW CI engine. Even though nanofuel produced better results, hydrogen induction was used to increase performance with reduced engine emissions further. At full load, 6 lpm hydrogen induction with the nanofuel produced 10.4% higher brake thermal efficiency, nearly 40% drop in CO, 39% drop in the UHC, and 22.22% drop in the smoke emission but 28% higher NOx emission compared to the petroleum diesel. Therefore, this combination is recommended for the CI engine operation with higher performance with reduced emissions and the transformer oil waste reduction in the environment of this application. • The waste transformer oil biodiesel blend with titanium dioxide nano particle (nano fuel of waste transformer oil) with hydrogen induction in the CI engine is possible in all loads. • Waste transformer oil to biodiesel, Titanium dioxide nano particles used nano fuel and hydrogen premixing were involved here. • At 7.5 lpm of hydrogen induction with the of waste transformer oil have 37.30% of brake thermal efficiency with 15.33% reduced BSFC. • It has 27.09% reduction in CO, 37.50% reduction in UHC emission and 28.53% reduction in the smoke opacity when compared with the diesel. • For the better performance hydrogen premixing is suggested with the nano fuel of the waste transformer oil. [ABSTRACT FROM AUTHOR]