Transformer Oil Research Articles

Degradation Assessment of In-Service Transformer Oil Based on Electrical and Chemical Properties

In order to ensure the long-term reliability and safety of power transformers, it is important to continuously monitor the characteristics of insulating oil, which not only helps in understanding its behavior over time but also ensures the safety of the equipment. The current study analyzes in-service insulating oil with the aim of relating deterioration and changes in the oil with service aging. Insulating oil samples were collected from three power transformers, with a voltage level of 220 kV and 132 kV, installed at a 220 kV substation. Electrical and chemical characteristics were obtained, and the impact of service aging and the relationships among load variation, oil, and winding temperatures with the characteristics were evaluated. Variations in the dielectric dissipation factor and breakdown voltage with service aging were recorded for all transformers, while the moisture content increased with each service year. Among the concentrations of gases present in the insulating oil, carbon monoxide, oxygen, and nitrogen concentrations increased after each service year. The impact of load variation on the breakdown voltage of the 132 kV transformer oil was more prominent than for the 220 kV transformers. The analysis of gas ratios and moisture content identified the degradation of cellulose insulation in all transformers, which was due to the presence of electrical faults.

Data-Driven-Based Full Recovery Technology and System for Transformer Insulating Oil

This study aims to develop an efficient recovery solution for waste transformer insulating oil, addressing the challenge of incomplete separation of residual oil in existing recovery technologies. A multi-module integrated system is constructed, comprising a waste oil extraction module, a residual oil vaporization module, an exhaust gas treatment module, and an online monitoring module. By combining steps such as oil extraction, residual oil absorption, hot air circulation heating, and negative-pressure low-frequency induction heating, the complete recovery of waste oil is achieved. The recovery process incorporates oil–gas saturation monitoring and an oil–gas precipitation assessment algorithm based on neural networks to enable intelligent control, ensuring thorough recovery of residual oil from transformers. The proposed system and methods demonstrate excellent recovery efficiency and environmental protection effects during the pre-treatment of waste transformer oil. Experiments conducted on 50 discarded transformers showed an average recovery efficiency exceeding 99%, with 49 transformers exhibiting no damage to core components after the recovery process. From a theoretical perspective, this research introduces monitoring and control methods for transformer insulating oil recovery, providing significant support for the green processing and reutilization of discarded transformer insulating oil. From an application value perspective, the recovery process helps reduce environmental pollution and facilitates the disassembly of transformers. This enables better analysis of transformer operating characteristics, thereby enhancing the reliability and safety of power systems.

Novel gas sensing mechanisms of Pd and Rh-doped h-BN monolayers for detecting dissolved gases (H2、CH4、and C2H4) in transformer oil

Detecting dissolved gases in transformer oil is crucial for assessing the operational status of transformers. The gas composition in transformer oil can reflect the health status of the equipment and help identify potential failure risks in a timely manner. Based on density functional theory (DFT), Pd and Rh atoms were doped into the h-BN monolayer, and the most stable adsorption structures for each were first explored. Then, the sensing performance of the Pd-doped and Rh-doped h-BN monolayers for H2, CH4, and C2H4 gases was analyzed. The results indicate that Pd-BN and Rh-BN exhibit enhanced sensitivity to H2 and C2H4 gases compared to pristine h-BN. However, they show poor adsorption characteristics for CH4. Both Pd-BN and Rh-BN demonstrate strong chemisorption for H2 and C2H4. In contrast, CH4 adsorption is predominantly physisorbed. The desorption time of H2 from Pd-BN at 398 K is 164 s, reflecting its excellent desorption performance. Additionally, Pd-BN and Rh-BN monolayers exhibit exceptional C2H4 capture capabilities, with adsorption energies of −1.697 eV and −2.188 eV, respectively, indicating their potential as C2H4 gas adsorbents. These findings provide theoretical insights for selecting materials for dissolved gas detection in oil and lay the groundwork for the development of Pd-BN and Rh-BN-based gas sensors.

Proposal of a new method for interpreting the concentrations of gases dissolved in mineral transformer oil

Proposal of a new method for interpreting the concentrations of gases dissolved in mineral transformer oil

Rotating flow over a vertical Riga plate with ramped heating using transformer oil

Rotating flow over a vertical Riga plate with ramped heating using transformer oil

Titanium Dioxide Nanoparticle-Loaded Silica Gel Spheres: A Superior Adsorbent for the Elimination of Trace Water in Transformer Oil

Titanium Dioxide Nanoparticle-Loaded Silica Gel Spheres: A Superior Adsorbent for the Elimination of Trace Water in Transformer Oil

The Influence of Iron Particle Contamination on the Breakdown Characteristics of Circulating Mineral Oil under DC Voltage

The presence of metallic particles can lead to the degradation of transformer oil due to the intensification of the electric fields near the conductive components. The primary objective of this research was to investigate the impact of iron impurities on the electrical properties of Mineral Oil (MO), particularly under conditions of continuous flow. Five distinct samples with varying levels of contaminants were carefully prepared for analysis. A specialized chamber was designed to replicate the circulation conditions of oil within an operating transformer. The focus of the investigation was on the breakdown characteristics under DC voltages. The results indicated that higher concentrations of iron impurities were associated with a reduction in breakdown voltage although the circulation of oil exhibited a beneficial effect. To validate these findings, Finite Element Method (FEM)-based simulations were conducted. The analysis of the electric field distribution revealed that iron impurities amplified the electric field intensity, while circulation served to mitigate this effect. Furthermore, the simulations tracking the trajectory of iron particles demonstrated that circulation hindered the particles from reaching the electrodes, thereby diminishing discharge events and lowering the risk of dielectric failure. In conclusion, the circulation of MO enhanced its breakdown voltage, although the presence of iron contamination could still pose a risk under DC voltage conditions.

Detection and continuous monitoring of moisture content in transformer oil using fractal-based capacitive sensor

Detection and continuous monitoring of moisture content in transformer oil using fractal-based capacitive sensor

Assessing transformer health through analysis of dissolved gases in cooling oil

Gases can form within the insulation system for various reasons while a transformer is in operation. If these gases are not promptly and properly managed, they can negatively impact the transformer's performance. Using the dissolved gas analysis (DGA) method to identify and assess the type and quantity of dissolved gases in transformer oil can uncover potential issues within the transformer. This information is crucial for guiding preventive maintenance and necessary repairs. Dissolved gas analysis testing was conducted by extracting transformer oil samples to identify signs of disturbances in the transformer based on the dissolved gas content. This research was conducted at the Paiton plant operations and maintenance services division. The condition of transformers was assessed by analyzing dissolved gases using the Rogers ratio method. Results indicate that the transformer at Paiton 9 is in good condition but overheating has occurred and requires treatment. Conversely, the transformers at Paiton 1 and 2 are in poor condition, showing signs of electrical faults and excessive heat. Despite several attempts to add inhibitors and conduct frequent testing, the transformers remained in poor condition, necessitating their replacement or repair.

An Outlier Robust Detection Method for Online Monitoring Data of Dissolved Gases in Transformer Oils

An Outlier Robust Detection Method for Online Monitoring Data of Dissolved Gases in Transformer Oils

Oleogel formation based on natural insoluble soybean fiber using capillary force: A novel strategy and application

Insoluble dietary fibers can be used as oleogelators to form oleogels via molecular self-assembly following chemical modification. However, the limitations of traditional chemical modifications and oleogel preparation methods significantly restrict their practical application. This study proposed a novel method to directly form edible oleogels using natural soybean insoluble fiber particles as oil-forming agents and water as a secondary fluid via the capillary suspension force between particles. The results showed that when the particle fraction was 15 % and the secondary fluid content was 0.2, a strong capillary suspension force could be formed to maintain the oil holding capacity of oleogels. The sedimentation coefficient analysis showed that adding particles and secondary fluids significantly affected the oleogel stability. The polarity of the oils, as well as the ionic strength and pH of the secondary fluids, influenced the rheological properties of oleogels, which correlated with the interfacial tension between the secondary fluids and oils. Moreover, the stable oleogels showed their potential as excellent solid fat substitutes in the preparation of breads (specific volume = 2.029 ± 0.114 cm3/g, weight loss = 12.2 ± 2.6 %, and hardness = 3.321 ± 0.055 N). This study highlighted that insoluble dietary fiber can form oleogels via capillary suspension, which is a relatively rapid and simple strategy. Additionally, it provided a solid foundation for the comprehensive utilization of soybean processing byproducts and the transformation of traditional food-specific oils and fats.

Application of metal organic frameworks ZIF-8-based solid catalyst with hierarchical porous structure and Brønsted-Lewis dual acid sites ionic liquids for sustainable biodiesel production from acidic soybean oil

In order to alleviate the mass transfer limitation of triglyceride macromolecules on the solid catalyst surface during the catalytic oil transformation process, the utilization of hierarchical porous solid catalyst is a feasible method. For reaching this goal, the hierarchical porous support of H-ZIF-8 was initially prepared by incorporating the three-dimensional ordered macro and mesoporous into the ZIF-8 using polystyrene spheres (PS) as a hard template. Subsequently, the phosphotungstate anion PW12O403- (PW) decorated sulfonated 4,4'-dipyridinium ionic liquid with Keggin structure, namely [DPySO3H]1.5PW, was encapsulated in the H-ZIF-8 support, with the formation of the novel [DPySO3H]1.5PW@H-ZIF-8 catalyst. The so-synthesized solid catalysts featured with ordered hierarchical porous structure and dual Lewis and Brønsted acidic properties, with large BET surface area of 267.38 m2/g. This catalyst had high catalytic performances for the concurrent transformation of triglycerides and free fatty acids to biodiesel in a heterogeneous manner. Under the optimal reaction parameters (methanol/oil molar ratio: 30:1; catalyst dosage: 4 wt%; reaction time: 8 h; reaction temperature: 130 °C), the oil conversion level of 91.2% and entire conversion of free fatty acids could be attained by applying this [DPySO3H]1.5PW@H-ZIF-8 catalyst. The high catalytic activity of this catalyst was due primarily to the increased mass transfer efficiency and synergism of Lewis and Brønsted acid sites. Moreover, the good FFA and moisture-resistance capacity was also shown for this catalyst even in the case of moisture content of 5 % and FFA content of 40 % in the oil feedstock. This solid catalyst could be reused by simple filtration and displayed good reusability, still attaining over 80% oil conversion at the fourth reuse cycles thanks to the robust interactions between the acidic active centers and the hierarchical porous support. The kinetic analysis indicated that the activation energy Ea and Arrhenius constant A for this solid acid-catalyzed transesterification process were 56.0 kJ/mol and 7.8×104 min-1, respectively. This research would provide a new approach for the development of hierarchical porous solid catalysts, enabling the one-step transformation of low-grade acidic oils into biodiesel in a more sustainable and environmentally friendly way.

Highly Sensitive and Stable In Situ Acetylene Detection in Transformer Oil Using Polyimide-Embedded Carbon Nanotubes.

This study presents an acetylene gas sensor capable of in situ monitoring transformer oils. This sensor utilizes carbon nanotubes (CNTs) embedded in polyimide (PI) synthesized by floating catalyst chemical vapor deposition. Unlike conventional sensors that target hydrocarbon gases dissolved in oil and measure the gas extracted from the oil, the proposed CNT-PI sensor detects gas within the oil in real time. The PI embedding technique effectively anchors and shields the CNT network against fluidic damage, ensuring stable sensing performance over 6 months, even under friction stress caused by oil convection. Decorating CNTs with gold nanoparticles further enhances the sensitivity and response of the sensor. The sensor achieves a high response (10.5% at 30ppm) and fast response/recovery times (28 s/77 s), Furthermore, the sensor demonstrates good response (10.4% at 30ppm) and moderate response/recovery times (444 s/670 s) in an oil medium, which qualifies for industrial applications. Additionally, a CNT-PI-based heater is integrated into the sensor as a multilayer component, maintaining an optimal operating temperature of 90 °C. The CNT-PI sensor demonstrates consistent gas-sensing performance even after 10,000 bending cycles and exhibits superior characteristics, indicating its compatibility with various forms of transformers.

GWO-elman based composite detection of transformer oil flow temperature

This paper addresses the issue of nonlinear coupling error caused by cross-sensitivity of strain and temperature in the composite detection of flow rate and temperature in transformer oil using a Fiber Bragg Grating (FBG) sensor. This paper focuses on the FBG sensor as the research object, elucidating the underlying principles of composite detection. Subsequently, a composite detection experimental platform is established for the purpose of analyzing the coupling error of flow rate and temperature. Ultimately, a nonlinear decoupling algorithm based on the Grey Wolf Optimizer (GWO) is proposed to enhance the nonlinear decoupling algorithm of the Elman neural network (simple recurrent neural network, Elman). The findings demonstrate that within the flow rate range of 0–5 m/s and the temperature range of 30 °C–150 °C, the maximum error is reduced by 72.0 % and 81.3 %, and the average error is reduced by 74.4 % and 79.4 %. This significantly enhances the precision and reliability of the sensor’s detection capabilities.

Experimental Investigation to Study Impact of Low-Concentration Hybrid ZnO and TiO<sub>2</sub> Nanoparticles on Thermo-Physical Properties of Transformer Oil

Transformer oil (Naphthenic Oil) is vital for the safe and efficient operation of transformer systems. The current experimental investigation mainly concentrates on the impact of low-concentration TiO2 and ZnO hybrid nanoparticles of 0.001 and 0.005 vol. % concentrations on the thermophysical properties of Naphthenic oil (Transformer oil). This investigation separately determines the flash and fire point, viscosity, thermal conductivity, pH, breakdown voltage and strength, and zeta potential analysis for both fresh and used Naphthenic oil and adding hybrid nanoparticles. The addition of hybrid nanoparticles to fresh and used Naphthenic oil increases the flash and fire points, viscosity, thermal conductivity, and pH values but the breakdown strength of the fresh oil decreases and the used oil increases.

Trace Acetylene Gas Detection Based on a Miniaturized Y-Sphere Coupled Photoacoustic Sensor.

In this work, a miniaturized Y-sphere coupled photoacoustic (YSCPA) sensor is proposed for trace C2H2 gas detection. The cavity volume of the designed YSCPA sensor is about 0.7 mL. The finite element method (FEM) has been performed to analyze the comparative performance of the YSCPA sensor and T-type PA sensor, indicating that the first-order resonance frequency (FORF) of the newly proposed YSCPA sensor has been reduced by half while the PA signal has been improved by a factor of 3 compared to the T-type PA sensor. C2H2 is employed as a target gas to test the performance of the YSCPA sensor. The experimental test results show that the response time of the gas is 26 s. The minimum detection limit (MDL) reaches 189 ppb at a lock-in integration time of 1 s. By extending the lock-in integration time to 100 s, the MDL of the designed PA sensor is reduced to 18.1 ppb. The designed YSCPA sensor has the advantages of small size, low gas consumption, simple structure, and high sensitivity, which is expected to be an effective solution for rapid and real-time monitoring of dissolved C2H2 gas in transformer oil.

Evolution laws of charge mobility of transformer oil and pressboard material with temperature and electric field strength

Abstract Charge mobility, a pivotal parameter in the space charge analysis model for oil-pressboard insulation of converter transformer under DC electric fields, predominantly relies on theoretical or empirical data. The prevalent omission of empirical, measurement-based evaluations, combined with the neglect of temperature and electric field intensity effects, introduces uncertainties in the calculation of electric field and charge dynamics. Grounded on the principles of the electroacoustic pulse technique for space charge measurements, our investigation established a temperature-controlled platform to determine the charge-charge mobility in oil and pressboard insulation mediums. Utilizing diverse oil-pressboard insulation systems, this study identified the temporal patterns of both positive and negative charge mobilities and unravelled the mechanisms modulated by temperature and electric field intensity: (1) with increasing temperatures (from 20 °C to 80 °C) and intensifying electric field strengths (from 5kV mm−1 to 25kV mm−1), the charge mobility within transformer oil and pressboard exhibits a rising trend. Notably, temperature variations exert the most significant influence, yielding amplifications up to 24.8 times. (2) The intrinsic properties of different transformer oils and oil-impregnated pressboards result in pronounced differences in their charge transport behaviors. Specifically, naphthenic-based oil demonstrates enhanced charge mobility relative to its paraffin-based counterpart. In contrast, transformer oils with higher kinematic viscosities exhibit diminished charge mobility compared to those with lower viscosities. (3) A linear relationship is observed between the oil absorption rate and electrical conductivity, aligning closely with the insulating pressboard’s charge mobility. The evaluation of electric field and interface charge dynamics in oil-pressboard insulation under both DC and polarity-reversed conditions revealed that the electric field decay in naphthenic-based oil is more rapid than in paraffin-based oils. Moreover, both the magnitude and rate of interface charge accumulation in naphthenic-based oils exceed those in paraffin-based variants, further validating the accuracy of our charge mobility measurements and ensuing analysis.

Conceptual Examination of Pt Atom-Adorned WTe2 for Improved Adsorption and Identification of CO and C2H4 in Dissolved Gas Analysis.

The online monitoring of transformer insulation is crucial for ensuring power system stability and safety. Dissolved gas analysis (DGA), employing highly sensitive gas sensors to detect dissolved gas in transformer oil, offers a promising means to assess equipment insulation performance. Based on density functional theory (DFT), platinum modification of a WTe2 monolayer was studied and the adsorption behavior of CO and C2H4 on the Pt-WTe2 monolayer was simulated. The results showed that the Pt atom could be firmly anchored to the W atoms in the WTe2 monolayer, with a binding energy of -3.12 eV. The Pt-WTe2 monolayer showed a trend toward chemical adsorption to CO and C2H4 with adsorption energies of -2.46 and -1.88 eV, respectively, highlighting a stronger ability of Pt-WTe2 to adsorb CO compared with C2H4. Analyses of the band structure (BS) and density of states (DOS) revealed altered electronic properties in the Pt-WTe2 monolayer after gas adsorption. The bandgap decreased to 1.082 eV in the CO system and 1.084 eV in the C2H4 system, indicating a stronger interaction of Pt-WTe2 with CO, corroborated by the analysis of DOS. Moreover, the observed change in work function (WF) was more significant in CO systems, suggesting the potential of Pt-WTe2 as a WF-based gas sensor for CO detection. This study unveils the gas-sensing potential of the Pt-WTe2 monolayer for transformer status evaluation, paving the way for the development of gas sensor preparation for DGA.

Assessing remaining life of reclaimed transformer oil with magnesium oxide absorbent for biorefinery sustainability

Assessing remaining life of reclaimed transformer oil with magnesium oxide absorbent for biorefinery sustainability

Theoretical Calculation of Dissolved Gas in Transformer Oil Using the Gas Sensitive Properties of Sc- and Ti-Modified ZrS2.

To guarantee the secure functioning of the complete power system and minimize the risks associated with oil-filled transformers during their operation, it is greatly important to carry out gas sensing studies of dissolved gases in transformer research. Through the utilization of first-principles density functional theory calculations, the adsorption energy, electronic characteristics, and recuperation duration of ZrS2 modified with Sc and Ti were examined. The results show that compared to those of the initial ZrS2 material, the doping of TM atoms Sc and Ti significantly improved the adsorption properties of the material, and the adsorption of CO and C2H4 showed chemisorption. The adsorption capacity for gases decrease in the following order: C2H4 > CO > H2. The calculated recovery times indicate that Sc-ZrS2 and Ti-ZrS2 were ideal carbon monoxide sensing materials under the specific conditions. The results of this work can establish a fundamental rationale for the use of ZrS2 in sensing the conditions of oil-immersed transformers.