Search

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.)

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 utilization of viscoelastic fluid is prevalent in various industries such as medical sector, food, petrochemical, and polymer due to its ability to reduce turbulent drag, exhibit elastic turbulence, and other notable characteristics. This aspect has consistently captured the attention of researchers. In the present study, the aim is to report the results associated with the Couette flow of viscoelastic rotating dusty nanofluids between rotating porous plates. Furthermore, in the present study, transformer oil is used as a base fluid, because to its numerous applications in power engineering and industrial sciences. Transformers are one of the crucial elements that requires high-level condition monitoring to ensure continuous power supply. Therefore, an effort is made to improve the critical features of the transformer oil by suspending nanodiamond and aluminum oxide nanoparticles, because the creation of transformer oil with desirable dielectric and thermal properties is in high demand due to its essential role in development. The governing equations for the above flow regime is modeled and formulated in terms of partial differential equations. A definite method (Poincare Light-Hill technique) is then used to solve the non-dimensional partial differential equations. The impact of different parameters on the temperature and velocity profiles are shown graphically. Nusselt number and Skin friction are computed and tabulated. The nanofluid velocity is observed to decline with raising suction parameter and magnetic field. It is noteworthy that the transformer oil's heat transfer rate is improved by 27.58 % for A l 2 O 3 nanoparticles and 31.27 % for nanodiamond particles, when the A l 2 O 3 and nanodiamond nanoparticles volume fraction is raised from 0.01 to 0.04 . This study has a wide range of applications in industrial science and engineering. This study also provides that how the nanofluids are using as a cooling agent. [ABSTRACT FROM AUTHOR]

Transformer oil, crucial for transformer and power system safety, demands effective monitoring. Aiming to address the problems of expensive and bulky equipment, poor real-time performance, and single parameter detection of traditional measurement methods, this study proposes a quartz tuning fork-based simultaneous measurement system for online monitoring of the density, viscosity, and dielectric constant of transformer oil. Based on the Butterworth–Van Dyke quartz tuning fork equivalent circuit model, a working mechanism of transformer oil density, viscosity, and dielectric constant was analyzed, and a measurement model for oil samples was obtained. A miniaturized simultaneous measurement system was designed based on a dedicated chip for vector current-voltage impedance analysis for data acquisition and a Savitzky–Golay filter for data filtering. A transformer oil test platform was built to verify the simultaneous measurement system. The results showed that the system has good repeatability, and the measurement errors of density, viscosity, and dielectric constant are lower than 2.00%, 5.50%, and 3.20%, respectively. The online and offline results showed that the system meets the requirements of the condition maintenance system for online monitoring accuracy and real-time detection. [ABSTRACT FROM AUTHOR]

In order to evaluate the damage to tunnel cables caused by fire caused by leakage of transformer oil into a cable channel, the fire characteristics of different volumes of transformer oil flowing into a cable channel were analyzed by numerical simulation. The results show that when the total leakage of transformer oil is less than or equal to 3 L, the fire will end within 120 s, and when the total leakage is greater than or equal to 5 L, the fire duration will exceed 900 s. When the leakage amount is 1 L, the cable only burns slightly, and when the leakage amount is 3~12 L, the cable burns obviously. The combustion of the cable is mainly concentrated between 15 s and 75 s, and the overall combustion rate of the cable increases first and then decreases. When the total leakage is greater than or equal to 8 L, the damage distance of the middle and lower layer cable is the smallest. When the total leakage is less than or equal to 5 L, the damage distance of the lower layer cable is the smallest, and the damage distance of the lower layer cable, middle and lower layer cable, and middle and upper layer cable is less than half of the length of the cable channel. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Donghua University (Natural Science Edition) is the property of Journal of Donghua University (Natural Science) Editorial Office 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.)

Oil-immersed transformers are widely used in power systems. When an arc fault occurs inside a transformer, the surrounding oil is rapidly pyrolyzed. These high-temperature, flammable gases are compressed into a high-pressure bubble, which is likely to cause tank deformations, explosions, and fires. Currently, related simulations on tank internal pressure and transformer fires are based on a constant gas composition, a constant gas production rate of 0.1 L/kJ, and a constant bubble temperature of 2000 K. This paper deals with a case of a power-frequency arc (5 kA, 30 mm, 80 ms) in transformer oil. The time-varying characteristics of pyrolyzed gas production, composition, and temperature are experimentally investigated. The percentage of hydrogen changes considerably, decreasing from 85.2 % to 70 %. The overall gas production rate increases slowly from 0.0574 L/kJ in the first 2.5 ms to 0.0982 L/kJ in 80 ms. The local temperature inside the main bubble (30 mm from the arc) decreases gradually from 2200 K to 1400 K, while the average bubble temperature decreases from 2550 K to 550 K. This case and these results provide an experimental basis for the parameter selections in the simulations about transformer internal pressure and fire progression.

The health of a transformer is affected by several aspects, including water content in transformer oil. Researchers have introduced various techniques for measuring water content in transformer oil. In the case of acoustical measurement, researchers typically utilize two ultrasonic sensors to detect acoustical parameters. This study proposes a novel technique to characterize transformer oil based on its water content using a single ultrasonic sensor. This technique employs an indirect measurement approach, where a substrate separates the oil from the sensor. The echoes from measurements are observed and presented in terms of three acoustical parameters, i.e., the acoustic speed, acoustic impedance, and density. Based on measurement results, the acoustic speed of the samples is successfully calculated from the time of flight. and the thickness of the chamber. However, only four materials used as substrate 1, i.e., 3mm, 5mm, 8mm acrylic, and 3mm glass, successfully produce similar plots of acoustic impedance and density.

China Power Grid is actively building a new energy-based ultra-high voltage grid system. Therefore, the researches on fire safety of power grid are of great importance. This paper firstly investigates the fire accident characteristics in the substation system. With the focuses on the transformer oil fires, the early detection and early warning, modification, fire monitoring and extinguishing systems of transformer oil are reviewed. It is found that the researches on flowing and jet fires should be reinforced while modified oil and pyrolysis gas detection can be applied for reducing the fire probability. Secondly, the fire risks and characteristics of cables are summarized for the transmission and distribution lines, and the methods of early warning, fire prevention and rescue are analyzed. For the wildfire threatening the transmission and distribution cables, the characteristics of wildfire and corresponding firefighting methods are reviewed. The water mist and liquid nitrogen are identified as the most effective ways of extinguishing cable fires and advanced fire detection and long-range drone fire extinguishing technologies should be improved for wildfires. Finally, the thermal runaway mechanism and fire characteristics of LIB in the energy storage system are summarized, and the difficulties in fire extinguishing are discussed. The application of the existing fire detection system in the field of LIB is proposed, and the early warning indicators for intelligent fire protection are introduced. In the future, the intelligent fire protection systems will improve the safety of energy storage systems, and efficient test platforms and reliable test standards will continue to be demanded to reduce the likelihood of thermal runaway and fire severity. [ABSTRACT FROM AUTHOR]

Transformer oil plays a critical role in ensuring the insulation and normal operation of power transformers. However, during operation, the transformer oil would undergo oxidation and degradation, leading to the formation of acids and polar compounds that increase its acidity and degrade its performance. Hence, the recycling and regeneration of aged transformer oil is an essential practice in transformer maintenance, contributing significantly to the extension of a transformer's operational lifespan and the reduction of potential risks. Adsorption separation is a preferred method for regeneration, offering simplicity and high efficiency. This study focuses on impregnated γ‐Al2O3 as an adsorbent for acidity removal in waste transformer oil. We conducted static adsorption experiments to investigate the optimal loading amount of the active component and the best calcination temperature for acid removal. XRD technique is employed to monitor the phase changes of the carrier during the calcination process. BET analysis is used to observe variations in the specific surface area and pore volume of the adsorbent during the modification process. DTG‐TGA is utilized to assess the weight loss during the calcination process. FTIR is employed to observe changes in functional groups during modification and adsorption processes. Along with these investigations, a study is also carried out to assess the dynamic acid removal performance of the acid‐removing adsorbent loaded into a fixed bed. The findings contribute to the development of sustainable methods for regenerating transformer oil, ensuring efficient and environmentally friendly operations. [ABSTRACT FROM AUTHOR]

In this study, we examine the effects of various shapes of nanoparticles in a steady flow of hybrid nanofluids between two stretchable rotating disks. The steady flow of hybrid nanofluids with transformer oil as the base fluid and Fe3O4+TiO2 as the hybrid nanofluid is considered. Several shapes of Fe3O4+TiO2 hybrid nanofluids, including sphere, brick, blade, cylinder, and platelet, are studied. Every shape exists in the same volume of a nanoparticle. The leading equations (partial differential equations (PDEs)) are transformed to the nonlinear ordinary differential equations (ODEs) with the help of similarity transformations. The system of equations takes the form of ODEs depending on the boundary conditions, whose solutions are computed numerically by the bvp4c MATLAB solver. The outputs are compared with the previous findings, and an intriguing pattern is discovered, such that the tangential velocity is increased for the rotation parameter, while it is decreased by the stretching values because of the lower disk. For the reaction rate parameter, the concentration boundary layer becomes shorter, and the activation energy component increases the rate at which mass transfers come to the higher disk but have the opposite effect on the bottom disk. The ranges of various parameters taken into account are Pr = 6.2, Re = 2, M = 1.0, ϕ1= ϕ2 = 0.03, K = 0.5, S = −0.1, Br = 0.3, Sc = 2.0, α1= 0.2, γ = 0.1, En = 2.0, and q = 1.0, and the rotation factor K is within the range of 0 to 1. [ABSTRACT FROM AUTHOR]

In this paper, an attempt to evaluate the effect of particles on the electrical conductivity of liquid dielectrics is made. For this purpose, a conductivity model is formulated taking into account the presence of relatively large charged microparticles in the dielectric. Based on calculations using the model, a comparative assessment of electrical conductivity was carried out. It is shown that in sufficient quantities, particles can significantly increase the electrical conductivity when forming double electric layers near their surface. [ABSTRACT FROM AUTHOR]

This study investigates the impact of incorporating TiO2 nanoparticles into two types of oils at different temperatures and with varying volume fractions: transformer oil (NYTRO LIBRA) and virgin coconut oil (manufactured by Govi Aruna Pvt. Ltd., Gampaha, Sri Lanka). The nanofluids were prepared using a two-step method by adding CTAB (cetyltrimethylammonium bromide) surfactant. To minimize nanoparticle agglomeration, this study employed relatively low-volume fractions. Thermal properties by means of thermal conductivity, thermal diffusivity, and volumetric heat capacity were measured in accordance with ASTM (American Society for Testing and Materials) standard methods using a multifunctional thermal conductivity meter (LAMBDA thermal conductivity meter). The measured thermal conductivity values were compared with theoretical models and previous research findings. It was confirmed that the modification of thermal properties was enhanced by doping TiO2 nanoparticles with different volume fractions. [ABSTRACT FROM AUTHOR]

This study is a numerical analysis of the transition process from the second to the third mode in transformer oil. In this study, it was determined how to change from the second to the third mode, which is thought to be a precursor to the process of electrical breakdown, which results in a significant loss of electrical energy and harm to electrical devices and equipment. The initiation time, length, rate of propagation velocity, and radius of the streamer discharge were determined. The transition from the second to the third mode during the electrical discharge process may lead to the occurrence of an electrical breakdown, which is one of the greatest challenges facing scientists and engineers who deal with the electrical power of transmission and generation devices. The model was designed by AutoCAD software, which included two electrodes: a needle, with a tip radius of (4μm), and a plate, with a gap of (1 mm) between them. The gap between the two electrodes was filled with transformer oil. The equations, which are Poisson's equation and the continuity equations for positive and negative ions and electrons, which are generated by applying an applied voltage (from 27 kV to within 278 kV), had been solved by a simulation process. All the schematics and drawings were extracted by the Comsol Multiphysics program. [ABSTRACT FROM AUTHOR]

The power transformer plays a crucial role in the power system’s network for distributing power. The efficient operation of power transformers is mainly based on the efficient liquid insulation used for cooling purposes. Mineral Oil (MO) derived from petroleum is traditionally used for insulation in power transformers. However, its lower thermal degradation and thermal conductivity may influence the performance of the transformer. The non-degradable property and low flash and fire points also affect environmental safety. The aforementioned attributes encouraged researchers to propose an alternative transformer oil for power transformers. In literature, various studies have been carried out to analyze Vegetable Oil (VO) as an alternative to petroleum-based MO; However, due to high viscosity, acidity may affect the performance of the transformer. Hence, this article proposes mixed MO with VO as an alternative for liquid insulation in power transformers. This study uses different ratios of coconut oil, palm oil and sunflower oil for investigation with MO. The experimental results show that the electrical, thermal, and physical properties of mixed transformer oil are better than those of MO and VOs. The results show that a higher proposition of VO has shown better performance. The thermal conductivity of mixed VOs with MO has increased by 6–10% compared to the MO. Both flash and fire points of mixed VO with MO increased by 50–70% compared to MO. The load has been performed to analyze the efficiency and operating temperature of the transformer; results show that the mixed VO with MO combination has 32.3% higher efficiency and 16°C lower operating temperature compared to MO. Further, the various aging characteristics of the transformer oil are also discussed in this study [ABSTRACT FROM AUTHOR]

This paper presents an experimental study of partial discharge activity in ferrofluids based on biodegradable transformer oil and iron oxide nanoparticles. Three ferrofluid samples with low, medium and high nanoparticle concentrations are employed in the research. The basic ferrofluid characterization is followed by a partial discharge experiment exposing the ferrofluids to a high voltage in a needle-plate electrode configuration. The analysis confirms that the apparent charge and number of discharges decrease with increasing nanoparticle concentration. These findings are interpreted with reference to the well-recognised electro-hydrodynamic streamer model. The charge trapping by nanoparticles hinders the ionization and discharge development. The study also focuses on the partial discharge activity in the ferrofluids under the action of a static magnetic field acting perpendicularly to the electric field. A decreasing trend in the number of discharges due to the magnetic field is revealed. A qualitative explanation is provided based on the field-induced cluster formation and charge mobility reduction. The presented experiment and the discussed findings may be valuable for practical application of the ferrofluid in high voltage equipment with a special need for partial discharge suppression.

The use of natural ester oils as electrically insulating fluids has gained significant attention from industries and electrical utilities as they aim to replace traditional mineral oils. However, most natural ester oils are derived from edible products, which has the potential to contribute to the food crisis. Therefore, nonedible green nanofluids made from cottonseed oil (CSO) have been targeted as a keen solution to this issue. However, Al2O3, TiO2, Fe2O3, SiO2, and graphene nanoparticles at (0.025, 0.05, and 0.075 wt/vol%) were used as additives, along with surfactant Olic Ac-id and Ethanol (1:5) due to their promising impact on the dielectric and thermal properties of the nanofluid. The nanofluid synthesis process was practically conducted in HV & Chemical Laboratories using one-step and two-step methods, and their breakdown voltage results and chemical properties (e.g., fire point, flash point, cloud point, pour point, viscosity, acidity, moisture content, resistivity, and dissipation factor) were compared. The physical mechanisms underlying these properties were also analyzed and tested. For the validation of the proposed vegetable oil the results have been compared with traditional mineral oil for high-voltage equipment's. The findings suggest that the proposed nonedible green nanofluids-based cottonseed oil (CSO) has a high potential to be used as electrically insulating fluids, providing a sustainable alternative to conventional mineral oils. Overall, this study provides insights into the use of non-edible green nanofluids as a solution to the potential contribution of natural ester oils to the food crisis. The findings highlight the importance of sustainable solutions in the energy industry and the need for further research in this area.

Transformers are one of the most important and expensive equipments in industries whose optimal performance has been influenced by various parameters such as weather conditions (temperature, humidity, etc.) and consumption patterns of the region. Transformer oils are one of the most vital materials used in this equipment. The oil of the transformer coils has been controlled by two factors: First, it acts as an electrical insulator between the coils and the body. Second, the heat created in the parts and the core of the transformer is transferred to the outside. In the electrical industry, many problems may be caused by transformers. Most of these cases have been affected by the performance of oils. In case of improper operation of the oil, it will cause disruption in electricity distribution and even damage and destruction. The oil should perform both tasks of cooling the transformer and insulating the body with electricity at the ideal level. However, due to the low thermal conductivity of such mineral oils, transformers cannot provide optimal performance. In this research by the simulation study, sufficient and acceptable information has been obtained to create the most optimal nano-oil in the operational range with comprehensive library reviews. On the other hand, according to the theoretical analysis, it has been presented that metal oxide nanoparticles, such as CuO, TiO2, Al2O3, SiO2, and MWCNT as hybrid NMs, have been used so far. The most important result of this study, in addition to the type of hybrid nanoparticles, is to find the best combination to increase thermal conductivity and the principles of electrical conductivity and standard indicators of transformer industries. To start the experimental design, the best and most optimal instruction is simulating the function of the transformer using different nano-oils by a computer. Then, in the next step, this simulation has been done by COMSOL software. So, first of all, precise prioritization for using different nanoparticles can be obtained.

Studying the breakdown characteristics of nano-modified transformer oil at low temperature is helpful to improve the breakdown voltage of transformer oil at low temperature. The breakdown characteristics of oil samples under different voltage forms, different temperatures and different water contents at-30 ∼30 °C were studied by using a relatively perfect test system. The results show that in the test temperature range, the breakdown voltage of the oil sample decreases first and then increases, and there is a minimum value. Under the three moisture contents of 26 ppm, 61 ppm and 85 ppm, the breakdown voltage of pure oil and nano-oil is the lowest when the moisture content is 85 ppm. The addition of nano-materials increases the breakdown voltage of oil samples, and the increase is small near zero degrees Celsius. When the water content is 26 ppm, the average increase rate is 8.57 %. The average increase rate is 14.35 %. The largest increase is above zero, with an average increase rate of 19.6 %. Nanomaterials reduce the dispersion of breakdown voltage of transformer oil. Compared with pure oil, the dispersion reduction rate is about 1.03.

As the focus tilts toward online detection methodologies for transformer oil aging, bypassing challenges associated with traditional offline methods, such as sample contamination and misinterpretation, fiber optic sensors are gaining traction due to their compact nature, cost-effectiveness, and resilience to electromagnetic disturbances that are typical in high-voltage environments. This study delves into the sensitivity analysis of intensity-modulated plastic optical fiber sensors. The investigation encompasses key determinants such as the influence of optical source wavelengths, noise response dynamics, ramifications of varying sensing lengths, and repeatability assessments. Our findings highlight that elongating sensing length detrimentally affects both linearity response and repeatability, largely attributed to a diminished resistance to noise. Additionally, the choice of the optical source wavelength proved to be a critical variable in assessing sensor sensitivity. [ABSTRACT FROM AUTHOR]

This paper proposes a method for recognising the fault type using a set of diagnostic criteria. Existing approaches to the interpretation of dissolved gas analysis (DGA) results usually rely on single diagnostic criteria. The proposed method solves the problems of incomplete use of diagnostic information and discrepancies in the norms and criteria for recognising the same fault inherent in the existing methods. The feature of the method is the analysis of the compliance of the DGA results of the diagnosed equipment with the ones of the equipment with a confirmed diagnosis from the fault database. This approach outperforms the existing methods in the number of faults recognised, allowing a wider range of faults to be detected, including combined faults. In addition, the method provides an opportunity to identify possible causes and localise the fault. This feature is unique and provides a significant advantage when interpreting DGA results. The proposed method demonstrates significantly higher accuracy (100%) in recognising various fault types, including combined faults, in comparison to existing methods (about 50%). The proposed method has a 60% success rate in determining the cause and location of a fault, but this figure depends on the database with faults of various types used. [ABSTRACT FROM AUTHOR]

Transformer oil is used to maintain the core and winding of the transformer. The main tasks of transformer oil as an industrial oil are insulation and cooling of a transformer. In the current study, the thermophysical and thermal properties of transformer oil nanofluid with volume percentages of 0.017% and 0.56% have been experimentally investigated which improves the performance of the base fluid due to the high thermal conductivity coefficient of carbon nanotubes compared to transformer oil. Ultrasonic baths and chemically functionalizing techniques were utilized in a two-step process to create nanofluids, which were stabilized by these techniques. In a double-tube carbon steel heat exchanger, the nanofluids were employed, and the thermal characteristics of the base fluid and nanofluids were evaluated. The findings indicated that the effective thermal conductivity improves with increasing temperature and CNT concentration, reaching its maximum value at a temperature of 45 °C in a volume fraction of 0.56. Observations showed that the heat transfer coefficient rose with rising Reynolds number and volume percentage, whereas the friction factor reduced when the hot fluid flowed at an intake temperature of 80 °C compared to the nanofluid in the outer tube. The flow rates for the nanofluids were calculated to be 0.2, 0.3, 0.4 lit/s, and 0.18 lit/s for the hot fluid, respectively. As a general conclusion, carbon nanotubes have a very high potential to improve the thermal performance of transformer oils, which is a serious challenge. [ABSTRACT FROM AUTHOR]

Geometrical inaccuracy is one of the electric discharge machining (EDM) errors and is mainly influenced by the dielectric being used during the operation. The non-conventional machining processes are opted over traditional machining operations due to the greater strength of Ni-based superalloy, specially, Inconel 617 (IN617). But still, there is a need to upgrade the dielectric fluid to minimize the overcut. Therefore, this study uses a combination of surfactant-added dielectrics of transformer oil and cryogenically treated (CT) electrodes (copper and brass). One of the exceptional benefits of applying the cryogenic treatment on the electrodes is that it refines the grain size of the electrode which helped in the regular sparking and reduced the dimensional inaccuracy throughout the EDM operation. A set of 20 experiments under the full factorial design technique was implemented. The experimental results have been explained with process physics, and along with simulation to explore the mechanism of machining with mathematical expressions. The machining capabilities of CT electrodes provided greater dimensional accuracy by an average of 17.1% compared to non-CT electrodes. CT brass provided the minimum dimensional inaccuracy (0.023 mm) in T-20. However, the non-CT copper electrode showed the lowest overcut (0.134 mm) obtained transformer oil without the addition of surfactant. The modeling was also performed to measure the crater sizes produced during the machining of Ni-based superalloy. The simulation results revealed that the mean absolute divergence between the current simulation findings and the ones provided in the literature was approximately equal to 5–7%. [ABSTRACT FROM AUTHOR]

It is known that in order to restrain the process of oxidation of transformer oil, and, accordingly, to extend its service life, an antioxidant additive ionol is added to it. Previously, specialists using the method of chromato-mass spectrometry established the fact of the formation of new phenolic compounds in oil along with the consumption of the inhibitory additive ionol, namely, 2,6-di-tert-butylphenol (2,6-DTBP) and 2, 6-di-tert-p-benzoquinone. These phenolic compounds, as well as ionol, belong to the class of sterically hindered phenols, which, in turn, are able to inhibit the oxidation of oil during its operation in oil-filled transformer equipment, in particular, power transformers and current transformers. This article presents results showing that as ionol is consumed, 2,6-di-tert-butylphenol accumulates in oil from transformers. To the greatest extent, this trend is noticeable for current transformers equipped with air-drying filters (the so-called "free breathing"). The formation of 2,6-DTBP in oil can serve as an indicator of accelerated aging of the oil as a result of its prolonged contact with atmospheric oxygen. Changes in additive concentrations during oil aging are controlled using a new technique developed by us, based on IR spectroscopy.

Transformer oil, crucial for transformer and power system safety, demands effective monitoring. Aiming to address the problems of expensive and bulky equipment, poor real-time performance, and single parameter detection of traditional measurement methods, this study proposes a quartz tuning fork-based simultaneous measurement system for online monitoring of the density, viscosity, and dielectric constant of transformer oil. Based on the Butterworth–Van Dyke quartz tuning fork equivalent circuit model, a working mechanism of transformer oil density, viscosity, and dielectric constant was analyzed, and a measurement model for oil samples was obtained. A miniaturized simultaneous measurement system was designed based on a dedicated chip for vector current-voltage impedance analysis for data acquisition and a Savitzky–Golay filter for data filtering. A transformer oil test platform was built to verify the simultaneous measurement system. The results showed that the system has good repeatability, and the measurement errors of density, viscosity, and dielectric constant are lower than 2.00%, 5.50%, and 3.20%, respectively. The online and offline results showed that the system meets the requirements of the condition maintenance system for online monitoring accuracy and real-time detection.

In order to evaluate the damage to tunnel cables caused by fire caused by leakage of transformer oil into a cable channel, the fire characteristics of different volumes of transformer oil flowing into a cable channel were analyzed by numerical simulation. The results show that when the total leakage of transformer oil is less than or equal to 3 L, the fire will end within 120 s, and when the total leakage is greater than or equal to 5 L, the fire duration will exceed 900 s. When the leakage amount is 1 L, the cable only burns slightly, and when the leakage amount is 3~12 L, the cable burns obviously. The combustion of the cable is mainly concentrated between 15 s and 75 s, and the overall combustion rate of the cable increases first and then decreases. When the total leakage is greater than or equal to 8 L, the damage distance of the middle and lower layer cable is the smallest. When the total leakage is less than or equal to 5 L, the damage distance of the lower layer cable is the smallest, and the damage distance of the lower layer cable, middle and lower layer cable, and middle and upper layer cable is less than half of the length of the cable channel.

Due to the aging of transformers during their service life, the dielectric resistance of transformer oils decreases. This dangerous situation, which may cause major power outages, needs to be analyzed well in detail. Transformer oils start to deteriorate due to the high electric field between the electrodes. The sharp points on the electrodes accelerate this deterioration process. Therefore, by correctly analyzing the effect of the electrodes on the oil, information about the insulation resistance of the liquid dielectric material can be obtained. In this study, electric fields and potential difference changes of transformer oil under uniform and non-uniform electric fields are investigated. Sphere-sphere electrode configurations were used to provide uniform field, sphere-rod, and rod-rod electrode configurations for non-uniform field effect. With the increase of the non-uniform field effect, higher electric field stress occurred in the transformer oil at the same voltage level. [ABSTRACT FROM AUTHOR]

This research presents a novel link between refractive index sensing and spectroscopy by designing a "photonic crystal fiber" based "refractive index ( RI )" sensor. The proposed sensor is based on the "surface plasmon resonance" phenomenon. The sensor monitors the transformer oil ( To ) moisture content as moisture depletes its quality. The change in the moisture content changes the RI of the transformer oil. Thus, the presented sensor can identify the minimal change in the RI of the To . The sensor is designed to operate in the RI range of 1.33 - 1.34 RIU , with a step size of 0.002. Using the wavelength interrogation method, the proposed sensor's wavelength sensitivity is 25,000 nm/RIU and 22,500 nm/RIU along X-polarization (X-pol.) and Y-polarization (Y-pol.), respectively. The amplitude interrogation technique is used to calculate the amplitude sensitivity obtained from the proposed sensor, which is 17080 RIU - 1 and 18690 RIU - 1 corresponding to X-pol. and -pol., respectively. The sensor resolution of the sensor is 4.00 × 10 - 6 RIU and 4.44 × 10 - 6 RIU corresponds to X-pol. and Y-pol., respectively. Full-width half maximum obtained from the proposed sensor is 73 nm and 55 nm for X- and Y-pol. , respectively. The figure of merit obtained from the presented sensor is 342.46 RIU - 1 and 409.09 RIU - 1 for X - and Y-pol., respectively. Thus, the prospective sensor can act as an ideal device for the quality assessment of To . [ABSTRACT FROM AUTHOR]

The interfacial tension is a crucial property of two-phase immiscible liquid. However, many researchers are not aware about the fact that its value is far from being constant for many pairs of liquids. The paper presents the measurements of interfacial tension time-dependencies for various oils against distilled water and assesses how it affects electrohydrodynamic processes in two-phase immiscible liquids. Primary results were obtained using an optical tensiometer (the pendant drop method). Further on, several computations of droplet electrodeformation were performed and compared to the relevant experimental data to independently check the reliability of the measurements. It was found that the decrease with time of the interfacial tension against water is specific for a lot of liquids, in particular, for many vegetable oils and even for transformer oils after it being used in power transformers. The change of the interfacial tension with time is shown to be a realistic cause for the emergence of the so-called cone-dimple mode of electrocoalescence, which was earlier reported in experimental studies. The paper includes experimentally measured properties (that need to be specified in numerical models) for many liquids. [ABSTRACT FROM AUTHOR]

Copyright of Electronic Processing of Materials / Elektronnaya Obrabotka Materialov is the property of Institute of Applied Physics 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.)

Polychlorinated Biphenyls (PCBs) are categorised as a type of persistent organic pollutants (POPs). In developing countries, transformer oils are the major sources of PCB release to the environment.. This study examined the pollution of PCBs from transformers of gas company cathodic protection stations in Qom province, during 2011. The PCBs were measured using the electrochemical method. According to the results, the PCBs concentration of transformers oil was ranged between 0 and 958 ppm. Most stations PCBs concentrations (over 60%) were higher than recommended level (50ppm) enacted by theDepartment of Environment (DOE) of Iran. The results showed that among all cathodic protection stations; 10.4% were in a safe level, 29.2% in precaution level, and 60.4% in dangerous level. ANOVA test presented the significant difference between levels of the PCBs in different stations (P < 0.05). It is recommended that proper and safe waste management strategies for the exposure, transportation, and storage for this type of waste be taken into account. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Chongqing University of Technology (Natural Science) is the property of Chongqing University of Technology 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.)

The detection of dissolved gas in transformer oil is of vital importance to diagnose the early fault and monitor the security and stability of power systems. In this work, distinct Pd/C, Pd/C-R and Pd/NC were synthesized and evaluated. XRD and XPS characterizations show that both Pd0 and PdII are presented over the surface of carbon host for Pd/C, while poor gas-sensitive properties were presented for Pd0 in H2-reduced Pd/C-R sample. High content of cationic PdII species are synthesized by nitrogen doping of the carbon surface for Pd/NC. The experimental results showed that the gas-sensitive performances of H2/CO/C2H2 gases is facilitated over the developed Pd/NC material. This study can provide reference for the rapid detection and fault diagnosis of faulty gases in transformers. [ABSTRACT FROM AUTHOR]

In this paper, a series of transformer oil jet fire experiments with different tanks of inner diameters (0.05 m/0.08 m/0.1 m), different filling rate (80%/100%) and different pool diameters (0.3 m/0.4 m) were carried out to study the radiation characteristics of transformer oil jet fire. The flame combustion characteristics such as the fire plume temperature, mass loss and radiant heat flux were measured and analyzed. The experimental results showed that: The shape of the transformer oil jet fire was approximately cylindrical. The radiant heat flux increased exponentially with the increased of flame height. And radiant heat flux decreased exponentially as the horizontal distance increased. The multi-point source model and the line source model performed well in the prediction of the fire radiant heat flux of the transformer oil jet. As the Froude number increased, the radiation fraction change could be divided into two stages. In the first stage, the radiation fraction maintained almost constant. In the second stage, the radiation fraction dropped significantly. The research results provided valuable data support for the fire protection design of substation equipment. In addition, it could effectively improve the fire prevention and control ability of substation personnel. [ABSTRACT FROM AUTHOR]