Synthetic Ester Oil Research Articles

Experimental studies on insulating oils for power transformer applications

Abstract 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.

Impact of silicon carbide, boron nitride, and zirconium dioxide nanoparticles on ester‐based dielectric fluids

AbstractThis research study investigates the influence of various nanoparticles on the dielectric breakdown voltage, oil dissipation factor, viscosity, and thermal conductivity of nanofluids. Nanofluids were prepared using synthetic ester oil as the base fluid, and three nanoparticles, silicon carbide (SiC), boron nitride (BN), and zirconium dioxide (ZrO2), were added at different concentrations (0.125 wt%, 0.250 wt%, and 0.375 wt%), which are basically the nano‐sized powder that can be blended in the oil. The dielectric breakdown voltage testing was conducted to evaluate the electrical performance of the nanofluids. Additionally, rheological measurements were performed to study the kinematic viscosity, while thermal conductivity was determined using appropriate techniques. The enhancements in each property were evaluated and compared for the different nanoparticle concentrations and types. Previous studies focused only on the investigation of the electrical properties of nanofluids. However, in the present study, the electrical as well as thermo‐physical characterisation of nanofluids is performed and analysed as they directly affect the cooling performance of transformers. The results provide dielectric and thermo‐physical characterisation that exhibit excellent insulation and cooling functionalities and valuable insights into the potential applications of nanofluids as dielectrics in various high‐voltage electrical equipment. ZrO2 and SiC nanoparticles exhibited a reduction in the oil dissipation factor. SiC consistently improved breakdown voltage (Bdv), while ZrO2 nanoparticles showed concentration‐dependent effects, enhancing Bdv at low concentrations but degrading it at higher ones. Unexpectedly, nanoparticle dispersion and lubrication effects can lead to viscosity reductions, countering conventional expectations. Surprisingly, at the highest concentration, the thermal conductivity decreases compared to the lower nano‐concentrations in synthetic ester oil.

Synthetic ester-based forced flow immersion cooling technique for fast discharging lithium-ion battery packs

Rapid advancements in Li-ion battery technology are being made to meet the growing demand for efficient energy storage solutions in electric vehicles and portable electronics. However, heat generation during rapid charging and discharging remains a significant challenge, as it can lead to overheating, fire, and explosion. To address this issue, battery thermal management systems require improvements in cooling strategies. This study aims to optimize the thermal performance of Li-ion battery packs during fast discharge operation by single-phase synthetic ester oil-based forced flow immersion cooling (FFIC) technique. The study analyzes the thermal performance of the FFIC of a 4S2P LIB pack based on various flow rates, pressure drops, and pump power consumption and compares it with various conventional cooling methods and dielectric fluids. The MSMD-based NTGK battery modeling approach is used to analyze the electrical and thermal characteristics of the battery pack at 3C discharge and environmental temperature of 25 °C. The simulation findings revealed that the synthetic ester oil has a superior cooling effect than mineral oil in the 4S2P Li-ion battery pack. The experimental results showed that the synthetic ester-based FFIC Li-ion battery pack achieves an optimal pack temperature of 31.3 °C and uniform temperature distribution at the flow rate of 5 L/min and pressure drop of 228.44 Pa. Moreover, FFIC reduces temperature rise by 51 % compared with natural air convection and 35 % compared with static flow immersion cooling (SFIC) in the 4S2P lithium-ion battery pack. Also, the practical significance of the SEO-based FFIC immersion cooling technique is assessed across extreme climate zones such as −10 °C and 40 °C and determined its superior performance in Li-ion batteries. Hence, this study proved that the FFIC technique is suitable for Li-ion batteries in electric vehicle applications in terms of optimal performance, reliability, and safety during high-current discharge operations.

Experimental and statistical investigation on the dielectric breakdown of magneto nanofluids for power applications

The insulating oil serves the dual purpose of providing insulation and cooling within transformers. This investigation aims to explore the impact of various nanoparticles on the dielectric breakdown voltage (BDV) of dielectric oils. The study examines the effect of the concentration of magnetic nanoparticles on the dielectric breakdown voltage of insulating oils. Nanoparticles such as iron (II, III) oxide (Fe3O4), cobalt (II, III) oxide (CO3O4), and ferrous phosphide (Fe3P) were utilized to create nanofluids with carrier mediums consisting of mineral oil and synthetic ester oil. BDV determination was conducted using a VDE and S–S electrode system according to IEC 60156 standards. Nanofluid were prepared using a two-step method, and their concentrations ranged from 0.01 g/L, 0.02 g/L, and 0.04 g/L in base oils. Twelve iterations were conducted for each prepared nanofluid, and breakdown voltage measurements were recorded. The results indicate a noteworthy enhancement in the breakdown voltage of nanofluids. The statistical analysis was performed on the dielectric property of nanofluid samples for better breakdown accuracy. The maximum enhancement at specific nanoparticle concentrations was shown by each nanofluid. The results show that under the S–S electrode configuration, the greatest overall enhancement was observed for Fe3P in mineral oil, with an enhancement of 70.05%, and Fe3O4 in synthetic ester oil, with an enhancement of 46.29%.

Surface reaction mechanisms research of Cun and Pdn (n=1–3) clusters modified MoSTe for fault gases in oil-immersed transformers

Efficient detection and timely resolution of internal faults within synthetic ester oil transformers are imperative for ensuring the stability of power systems. This paper proposes the utilization of MoSTe monolayer modified with Cun and Pdn (n=1–3) clusters for detecting internal fault gases (C2H2, C2H4, and CH4) in transformers. The adsorption mechanism and electronic properties of target gases on the modified substrate surface are systematically studied through density functional theory analysis of adsorption energy, density of states, and deformation charge density. The results indicate that TMn clusters possess the capability to enhance the reactivity of the MoSTe surface, leading to varying degrees of improvement in conductivity and adsorption capacity. Different target gases exhibit distinct adsorption characteristics, with the modified monolayer showing strong adsorption capabilities for C2H2 and C2H4. The calculation of work function and recovery time further reveal the promising potential of Pdn-MoSTe monolayer as resistive gas sensing materials for detecting C2H2 and C2H4, while Cun-MoSTe monolayer are also identified as high-quality candidates for C2H4 sensing materials. This study is expected to facilitate the practical application of MoSTe monolayer in the field of transformer operational state monitoring, providing new insights for exploring novel gas sensing materials.

Differential Low-Temperature AC Breakdown Between Synthetic Ester and Mineral Oils: Insights From Both Molecular Dynamics and Quantum Mechanics

Differential Low-Temperature AC Breakdown Between Synthetic Ester and Mineral Oils: Insights From Both Molecular Dynamics and Quantum Mechanics

A numerical study on effect of intra and inter spaced winding configuration on performance of oil forced transformer cooling system

The present work aims at investigating, numerically, the heat transfer characteristics of transformer cooling system under forced circulation for three different winding configurations. The purpose of a transformer cooling system is to keep the hot spot temperature within the critical value for a long life of transformer, which increases with enhanced cooling of transformer windings. Thus, two different winding configurations are modeled by providing space within the windings (an intra-space model) and in between the windings (an inter-space model) to improve the fluid-solid interaction. A conventional winding, without spacing, is also modeled for comparative study. A 315 kVA, 3-phase core type transformer is taken as the base model from which the winding and core specifications are obtained analytically. Parameters chosen to measure the influence of winding configuration are local temperature distribution in the windings and core and maximum transformer temperature. Results are obtained for all three models with varying space for various cooling mediums like naphthenic oil, silicon oil, and synthetic ester oil at flow velocities ranging from 0.72 m/s to 2.16 m/s. It is observed that the gap between the windings, interspacing, decreases the secondary winding temperatures, while it increases the core and primary winding temperatures. However, the intra spacing configuration finds a drop in local temperatures at all locations of the transformer windings and core. The enhanced heat dissipation to the cooling agent, with intra spacing winding configuration, reduces the maximum transformer temperature. Contrasting to the above, the inter-space model has an adverse effect on maximum temperature at all widths of space considered. Quantitatively, the space within the transformer reduces the maximum temperature by 5% in comparison with the space between the windings. The increased velocity of the cooling medium, Naphthenic oil, from 0.72 m/s to 2.16 m/s reduces the maximum temperature by 4.5 units. The study made to know the role of cooling medium discloses that the synthetic ester oil shows better performance for reducing temperature values due to its highly viscous nature.

High-performance protic ionic liquids as additives in lubricating oils with varying polarity

Although ionic liquids (ILs) have proven to be multifunctional and universal lubricant additives, their solubility in different polar lubricating oils varies greatly. This variability restrains their widespread use as general-purpose lubricating additives. To address this issue, three protic ionic liquids (PILs) with high solubility in lubricating oils with differing polarities were selected as additives, and their tribological performances in polyethylene glycol (PEG) and synthetic pentaerythritol carboxylic ester oil (5750) were systematically investigated. These findings were interesting, as PILs effectively improved the lubrication properties of PEG but impaired those of 5750. Additionally, a variety of surface analysis techniques and MD simulation were employed to further explore the lubrication mechanisms of PILs, and results indicated that they exhibited distinct tribological performance.

Comparative analysis of AC breakdown properties of Jatropha-based ester and other insulating oils: commercial natural ester, synthetic ester, and mineral oil

Comparative analysis of AC breakdown properties of Jatropha-based ester and other insulating oils: commercial natural ester, synthetic ester, and mineral oil

Investigation of CeO2 nanoparticles on the performance enhancement of insulating oils

Integrating nanotechnology in dielectric fluid significantly inhibits losses and boosts overall dielectric fluid performance. There has been research done on the effects of introducing various nanoparticles, such as titania, alumina, silica nanodiamonds, etc. In this paper, a novel nanoparticle, Ceria (CeO2), has been used, and its properties were examined using the FTIR (Fourier Transform Infrared) spectrum, the XRD (X-ray Diffraction) spectrum, the SEM (Scanning Electron Microscopy), and the TEM (Transmission Electron Microscopy). This paper illustrates an efficient dielectric fluid prepared by the successful dispersion of Cerium Oxide (CeO2) nanoparticles in various concentrations into four commercial oils, namely mineral oil, rapeseed oil, synthetic ester oil, and soybean oil, to enhance and improve their dielectric characteristics. The performance investigation emphasises breakdown strength enhancement and other dielectric properties of the colloidal solution comprising different nanoparticle (NP) concentrations. Various commercial oils are used as a base in nano-oil to diversify their applicability as dielectric fluids by measuring the correlation in dielectric parameters and statistically assessing their applicability with normal and Weibull distributions. The obtained experimental data sets were analyzed using the Statistics and Machine Learning Toolbox in MATLAB. The aging measurement has been done only on mineral oil, and results were matched using a predictive model of statistics and the Machine Learning Toolbox in MATLAB. Well-dispersed CeO2 NPs in the insulating oils lead to a significant increase in AC breakdown strength. The effect of ageing on the dielectric properties of nano oils yields better results than conventionally aged oil. It has been observed that the breakdown voltage is enhanced by up to 30% for mineral oil at an optimal concentration of 0.01 g/L, 9% for synthetic ester oil at 0.03 g/L, 18% for rapeseed oil at 0.02 g/L, and 19% for soybean oil at 0.03 g/L nanoparticle concentration. Following the dispersion of CeO2 nanoparticles, the dielectric constant of all insulating oils has also significantly improved.The overall experimental results are promising and show the potential of the CeO2 NPs-based nano oil as an efficient and highly performing dielectric oil for different power applications.

Comparison of negative streamer development in synthetic ester and mineral oil in a point-sphere gap divided by a pressboard barrier

This article presents the results of the studies on development of negative streamers in synthetic ester and mineral oil with electrode system using a pressboard barrier. The tests were performed at standard lightning impulse voltage in point-sphere electrode configuration as reference system and a 5 mm thick pressboard barrier placed in different locations between the point and the sphere. Introducing pressboard between the electrodes allowed to relate the observations to the real insulating systems where long oil gaps are divided on shorter by insulating barriers. It was done to show whether pressboard barrier changes the streamers behavior in the considered electrode gap distance what is important from the viewpoint of assessment of dielectric properties of alternative liquids versus mineral oils. The results showed that the pressboard barrier for both liquids tested prevents breakdown. In addition, the barrier causes reduction of the propagation velocity of the streamers in synthetic ester, which is benefit in relation to the results concerning free liquid gaps.

Influence of Mineral Oil-Based Nanofluids on the Temperature Distribution and Generated Heat Energy Inside Minimum Oil Circuit Breaker in Making Process.

The enhancement of the thermal properties of insulating oils has positively reflected on the performance of the electrical equipment that contains these oils. Nanomaterial science plays an influential role in enhancing the different properties of liquids, especially insulating oils. Although a minimum oil circuit breaker (MOCB) is one of the oldest circuit breakers in the electrical network, improving the insulating oil properties develops its performance to overcome some of its troubles. In this paper, 66 kV MOCB is modeled by COMSOL Multiphysics software. The internal temperature and the internally generated heat energy inside the MOCB during the making process of its contacts are simulated at different positions of the movable contact. This simulation is introduced for different modified insulating oils (mineral oil and synthetic ester oil) with different types of nanoparticles at different concentrations (0.0, 0.0025, 0.005, and 0.01 wt%). From the obtained results, it is noticed that the thermal stress on the MOCB can be reduced by the use of high thermal conductivity insulating oils. Nano/insulating oils decrease internal temperature and generate heat energy inside the MOCB by about 17.5%. The corresponding physical mechanisms are clarified considering the thermophoresis effect.

Molecular dynamics study on thermal decomposition characteristics of synthetic ester oil

The synthetic ester oil has great application potential in liquid insulation of traction transformer due to its excellent insulation performance. In this paper, molecular dynamics simulations were performed using the ReaxFF reaction force field to study the thermal decomposition mechanism and product distribution of synthetic ester oils. The results show that the initial decomposition reaction is ester bond cleavage, followed by the decarboxylation reaction and β-C bond cleavage; the main decomposition products are CO2, C2H4 and some C2 and C3 species; by studying the effect of temperature on the product distribution, it is found that CO2 and C2H4 are stable products of thermal decomposition, while some small molecular hydrocarbons such as CH4 and H2 are products at different temperatures. By studying the generation process of these dissolved gases, it is possible to provide a theoretical basis for the research on the DGA method of synthetic ester oil.

Effects of Thermal Aging on Blended Oil Characteristics in Comparison to Mineral Oil and Synthetic Esters

The paper aims to investigate the long-term behavior of insulating oil in high-voltage applications by analyzing and correlating the changes in its physicochemical properties over the high-temperature range. To comprehend the rate of oil degradation, uninhibited mineral oil (MO), blended oil (MSO), and synthetic ester (SE) have been exposed to enhanced thermal stresses in combination with solid insulation. In compliance with IEEE C57.100, a five-point aging mechanism for thermal aging was taken into account. Thermal stresses ranging from 100 to 195 °C were applied continuously for 168 hours with a temperature variation of 25 °C. The effects of thermal stress have been deliberated by analyzing changes in physicochemical properties, such as density, kinematic viscosity, acidity, flash point, and visual observation of the mineral oil, synthetic ester, and mixed oil. The results demonstrated that the inclusion of esters into mineral oil enhances its characteristics and functionality and accentuates its suitability for assessing the state of high-voltage transformers.

An Experimental Study and Statistical Analysis on the Electrical Properties of Synthetic Ester-Based Nanofluids

The rise in power demand today necessitates its generation and transmission at high voltages. The efficient transmission of electric power requires transformers with an insulation system that exhibits excellent dielectric properties. In this paper ZnO and CuO nanomaterials are utilized to investigate the dielectric characteristics of pure synthetic ester oil and its related nanofluids (NFs) from room temperature up to 60 °C at increments of 20 °C, including AC breakdown voltage, Dielectric Dissipation factor, and DC resistivity. The breakdown testing is carried out in accordance with experimental IEC-60156 requirements. The DC resistivity and dissipation factor of oils are measured using the Dissipation Factor meter, resistivity meter, and a heating chamber with an oil cell that follows IEC 60247 standard. The statistical analysis is performed on the breakdown voltages test values using the Weibull probability distribution model for better accuracy. From the results, it has been found that ZnO nanofluid possesses a higher breakdown voltage among all the tested liquids. Furthermore CuO nanofluid gives a minimum value of dissipation factor even at higher temperatures.

Modified Tamanu Plant-Based Oil From Pahang Malaysia as Biodegradable Metalworking Fluids

Metalworking fluid (MWF) is a cooling and lubrication agent for the machining process. It is used as a coolant for rapid heat removal and provides a lubrication mechanism at the cutting zone. However, commercial MWFs such as synthetic ester and mineral oil give negative effects on human health and the environment. Therefore, the manufacturing industry should substitute commercial oil with vegetable-based oil. Calophyllum Inophyllum or also known as Tamanu is one of the feasible plant that has abundant oil quantity. In this study, modified Tamanu based oil with Trimethylolpropane ester (MTO) and modified Tamanu based oil with Pentaerythritol ester (MTOP) have been prepared and tested for their physical and tribological properties. Two types of ionic liquids; Phosphonium-based ionic liquid (PIL) and Ammonium-based ionic liquid (AIL) were added to each Tamanu-based oil (MTO and MTOP) to enhance their physical and tribological properties. Physical tests and Fourier Transform Infrared spectrometry (FTIR) were performed on each lubricant samples. The obtained results have shown that there is high viscosity index in MTOP + PIL 1 % and a lower double bond value in MTOP oil. MTOP + PIL 1 % has shown improvement in its tribological properties and can be comparable with commercial oil. Thus, it is suitable to be used as a substitute for commercial metalworking fluid in corresponding to green manufacturing activity.

Study of chemical properties of insulation mixtures to be used in high-voltage equipment

Reliable operation of high-voltage oil-filled equipment directly depends on the condition of the insulation. One of the main components of the insulation system is transformer oil, which has been used for more than 120 years. However, in the light of modern requirements for insulating materials, oil is significantly inferior to synthetic esters in terms of such properties as chemical stability, environmental safety and high fire resistance. At present, the mixing of synthetic ester and transformer oil can be considered as one of the ways to improve the properties of the latter. A change in the chemical properties of an insulating liquid during its aging, and, consequently, the formation of various impurities and a change in the structure of its component composition will also affect the electrical insulating characteristics of the liquid dielectric. And the more the liquid is oxidized, the more significantly the electrophysical parameters worsen, including the main parameter — electrical strength (or breakdown voltage).This paper presents the results of a study of the chemical properties of mixtures of oil and synthetic ester during prolonged exposure to elevated temperatures. The assessment of the quality of insulating mixtures was carried out by changing such indicators as optical turbidity, acid value, ester value, peroxide value, surface tension and corrosiveness. Fluid testing results in this study indicate that blending of synthetic ester with aromatic oil at 10% and 20% (v/v) results in mixtures that show signs of a colloidal system. This is evidenced by atypical trends in the diagrams indicating the change in peroxide value, acid value and optical turbidity during their aging at a temperature of 110ºС with free access of air to the surface of the mixture. Increasing the proportion of ester in the mixture to 30% and above leads to stabilization or slowdown of chemical reactions occurring due to thermal-oxidative effects. Under thermal exposure (without air access), the addition of synthetic ester to the aromatic oil in a volume of 30% or more significantly reduces the likelihood of sediment formation due to the destruction and polycondensation of aromatic hydrocarbons in mineral oil.

Characterization of Ion Transport Properties in Synthetic Ester Oil by Polarization Current and Dielectric Spectroscopy

The accurate estimation of the charge carrier mobility in synthetic ester oil-based insulation systems is required for the reliable prediction of the electric field induced by dc voltages. Some discordance is observed in the literature, therefore, this quantity is investigated by two alternative methods. First, the mobility is estimated in a material sample by measuring the polarization current and the ion time-of- ight during a voltage polarity reversal test. Next, the mobility is derived from the frequency-dependent loss tangent measured by dielectric spectroscopy. The values obtained by the two methods are consistent, in the range of ≈ 2-4·10^-10 [m2/Vs] at 303 K.

Analysis of the Impregnation Process of Cellulose Materials by Using Ester-Based Liquids and Mineral Oil

Nowadays, new alternative of dielectric liquids with biodegradable characteristics has been considered to replace conventional mineral oil in both distribution and power transformer applications. However, there are some manufacturing processes that need to be modified to incorporate these ecological fluids, mainly in power transformers. Ester liquids, either natural or synthetic, show higher viscosity than mineral oil; therefore, a significant impact on the impregnation process of insulation materials is expected. In this work, the impregnation process of cellulose insulation is investigated by using three different liquids: natural ester (NE), synthetic ester (SE), and mineral oil. Laboratory tests were carried out using insulation blocks and pressboard samples to evaluate the influence of each fluid in the cellulose material. It is shown that the impregnation process with ester liquids is longer than mineral oil, at room temperature; however, it could be reduced by increasing the temperature of the ester liquid.

Preparation and performance evaluation of an ester‐bridged antioxidant used as multifunctional additive in ester oil

AbstractThis study aims to investigate a novel high‐efficient antioxidant for synthetic ester oils. An ester‐bridged antioxidant, phloroglucinol tris (3‐[3,5‐di‐tert‐butyl‐4‐hydroxyphenyl]) propionate (PTP), was successfully synthesised in high yield under relatively mild reaction conditions. Thermal stability and oxidation resistance of diisooctyl adipate (DOA) ester oil were determined and compared to the typical commercial phenol antioxidants, including its tribological properties. The results indicate that the prepared PTP antioxidant exhibits considerably higher thermal stability than commercial antioxidants, and it also improves the oxidation resistance of the synthetic ester oil more effectively. Moreover, the addition of PTP antioxidant enhanced the wear protection of DOA ester oil without deteriorating its lubricating performance. The ester‐bridged antioxidant can be used as a multifunctional additive, which not only exerts excellent thermal stability and oxidation resistance, but can also act as an efficient anti‐wear agent in synthetic ester oils.