Traditional Mineral Oil Research Articles

Comparative study on lubrication properties of biodiesel and bio-lubricant trans-esterified from desert seed oil with conventional lubricants

In recent years, there has been an increasing focus on renewable and biodegradable energy sources among lubricant manufacturers due to the environmental impacts and limited availability of fossil-based engine oils. Biomass sources present a cost-effective and eco-friendly alternative to traditional mineral oil sources. This study aims to produce and characterize biodiesel and biolubricant from desert date seed oil through transesterification. The result of the study was compared with the properties of conventional and commercial lubricants. The study employed transesterification to convert desert date seed oil into biodiesel and biolubricant. The produced biolubricant and biodiesel were characterized to determine their kinematic viscosity at 40°C, specific gravity, flash point, and pour point. These properties were then compared with those of other bio-lubricants and commercial base lubricants. For biodiesel, the yield was 56%, with a favorable acid value (0.98 mg KOH/g), iodine value (43.41 mg/g), and saponification value (197.4 mg KOH/g). Although, the specific gravity (1.876) was higher than ASTM standard. However, the flash point (112°C) and cloud point (11°C) were within acceptable ranges. The biolubricant produced from desert date oil showed promising results with a high kinematic viscosity of 67.54 mm2/s, a specific gravity of 1.876, a flash point of 120°C and a pour point (−5°C). These results obviously suggest the produced lubricant a suitable for automotive applications possessing good low-temperature performance. The flash point result and the physicochemical properties of the oil aligned well with industrial standards. The comparisons revealed that the produced biolubricant closely matched the properties of SAE VG 220 and SAE VG 40. The findings suggest that the biolubricant and biodiesel derived from desert date seed oil can serve as a viable substitute for petroleum-based lubricants in light gear applications and can be effectively used in two-stroke engines, providing a sustainable alternative to conventional lubricants.

Enhancement of Dielectric Properties of Echo-Friendly Cottonseed Oil-based Nanofluids for High Voltages

This study investigates the performance of nanofluid-based vegetable oil (VO) as an advanced dielectric medium for high-voltage equipment, with a specific focus on AC breakdown voltage (AC BDV). Nanofluids, comprising carefully selected nanoparticles (including Al2O3, TiO2, Fe2O3, SiO2, and Graphene) dispersed in cottonseed oil (CSO), offer a unique opportunity to enhance the dielectric properties of insulating fluids. Through a systematic experimental approach, AC BDV tests were conducted in Khwaja Fareed UEIT High Voltage Laboratory, and the results were compared to with traditional mineral oil (MO) for high-voltage equipment’s. The findings reveal significant improvements in the AC BDV of the nanofluid, demonstrating its enhanced electrical insulation capabilities. This study displays nanofluids based on VO as a promising alternative for enhancing high-voltage equipment's electrical performance while considering the environment. Implementing nanofluids effectively improves the dielectric properties of insulating fluids, contributing to advancements in high voltage equipment technology.

Analysing the Suitability of Using Different Biodegradable Fluids for Power Transformers with Thermally Upgraded Paper

Mineral oil has been used for many years in various electrical equipment, including transformers, as a cooling and insulation medium. However, its low biodegradability and poor performance in terms of fire protection have prompted the search for fluids to replace it, with vegetable oils being prominently considered. In this study, the dielectric, chemical, and physical properties of four vegetable oils obtained from different seeds (sunflower, rapeseed, soybean, and palm) and a biodegradable synthetic fluid are analysed throughout their lifespan in transformers. Their performances are compared with a traditional mineral oil to assess which one is more suitable for use in transformers employing this type of paper. To achieve this, the fluids were subjected to thermal ageing in combination with copper and a thermally upgraded kraft (TUK) paper, with its degradation controlled by measuring the degree of polymerisation. The results demonstrate that the origin of the vegetable oils affects their properties and degradation rates. It was found that most of the alternative fluids are suitable for use in transformers with the TUK paper and that they can increase their lifespan.

Up-gradation of the dielectric, physical & chemical properties of cottonseed-based, non-edible green nanofluids as sustainable alternatives for high-voltage equipment's insulation fluids

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.

Investigation of Vegetable Oil Blended with Mineral Oil

Oil-based commodities have long dominated the world's energy needs across a variety of industries.. Vegetable-based ester oil is provided as an environmentally friendly substitute for traditional mineral oil for fluid protection. In order to evaluate the essential characteristics of blended liquid as liquid insulation, various ratios of mineral and ester oil were combined in this study. Studies are being conducted on sunflower, safflower, and rice bran oils. Tests are carried out on viscosity, breakdown voltage, flash point, and pour point for different combinations in accordance with industry standards (IEC and ASTM). The study found that blended mixes exhibit quality fluctuations that suggest hopeful signs for mineral oil replacement.

Decomposition and gas production characteristics of vegetable insulating oil under thermal stress

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

Evaluation of palm kernel oil as lubricants in cylindrical turning of AISI 304 austenitic stainless steel using Taguchi-grey relational methodology

The disadvantages of the conventional cutting fluids such as mineral oil have prompted the search for eco-friendly cutting fluids. Vegetable oils have often been recommended as environmentally friendly substitutes for traditional mineral oil. The current study examined the performance of palm kernel oil (PKO) and its mineral oil during the turning of AISI 304 steel using the minimum quantity lubrication (MQL) technique. Six litres of crude PKO were extracted from palm kernel seeds through a mechanical extraction technique. Taguchi L9 (3)3 orthogonal array was considered for the experiment. The depth of cut (DC), feed rate (FR), and spindle speed (SS) are the cutting parameters while cutting temperature (CT) and surface roughness (SR) are the response characteristics. Experimental results showed that the mineral oil outperformed the PKO in terms of SR with an improvement of 48.2%. The improvement of PKO over mineral oil is approximately 0.89% in terms of cutting temperature. The highest turning temperature of mineral oil was 67.333 °C, while that of PKO was 67.8 °C. In general, the performance of PKO shows it can be a good replacement for mineral oil if produced industrially with adequate additives. The grey relational analysis (GRA) showed that the optimum DC, FR, and SS for palm kernel and mineral oils are 1.25 mm, 0.25 mm rev−1 and 870 rev min−1, and 1.25 mm, 0.10 mm rev−1, and 870 rev min−1, respectively. The results of this study demonstrated an experimental basis for the application of PKO minimal quantity lubrication turning and validated the efficacy of the integrated Taguchi-grey relational analysis (TGRA) optimization approach.

Experimental Study of the Electrical and Physiochemical Properties of Different Types of Crude Palm Oils as Dielectric Insulating Fluids in Transformers

This paper gives information on the electrical and physiochemical characteristics of six different types of palm oil compared with traditional mineral oil. We found that natural processed crude palm oil (PO-C) had a higher resistance to AC breakdown voltage than other types of palm oil, including traditional mineral oil. The results of the positive lightning impulse voltage test for PO-C were still the highest compared to other types of palm oil, including traditional mineral oil, at 58.26%. The summarised dissipation factors of all tested crude palm oils were significantly higher than those of mineral oils, which will make the palm oil less insulating, especially in PO-A palm oil (36.197%), where the values were higher than those of other oils, while mineral oil has a slightly increased dispersion factor. For relative permittivity, all palm oils were compared, and it was found that PO-C had a lower relative permittivity than the other oils. In terms of physical and chemical properties, in the moisture content test on all oils, PO-C had the percentile with the highest moisture content decrease of 58.74%. In the case of testing the surface tension value, it was found that traditional mineral oil had the highest value (48.46 m/Nm) when compared to palm oil. On the other hand, the acidity in traditional mineral oil is the lowest (0.03 mg KOH/g) compared to all palm oils. Results from studies demonstrate the possibility of using natural processed crude palm oil, or PO-C, as a replacement for traditional mineral oil. This is consistent with the results of electrical properties that show PO-C is higher than other types of palm oil and includes traditional mineral oil.

Dissolved gas analysis and dissipation factor measurement of mineral oil‐based nanofluids under thermal and electrical faults

AbstractMineral oil is the most frequent insulating liquid used in oil‐immersed transformers for electrical insulation and heat dissipation. However, oil‐based nanofluids are becoming more popular in scientific research as they have proved to have better dielectric and thermal characteristics. When applying these nanofluids into actual transformers, they would be exposed to thermal and electrical stresses. Thus, The aim of the authors is to investigate the generation pattern of dissolved gases in nanofluids under thermal and electrical faults and to assess the applicability of traditional Dissolved Gas Analysis (DGA) techniques if oil‐based nanofluids are used in transformers. Oil‐based nanofluid samples were prepared using a magnetic stirrer and an ultrasonic homogeniser and then subjected to simulated thermal and electrical faults in the laboratory using properly sealed test cells. Three types of metal oxides, Silicon dioxide, Titanium dioxide, and Aluminium oxide nanoparticles, have been used to prepare nanofluids with 0.02 g/L and 0.04 g/L concentrations. The gases released and dissolved into oil due to the simulated faults were analysed and compared to traditional mineral oil as a benchmark. The dielectric dissipation factor was obtained and analysed for all samples. According to the findings, the presence and concentration of nanoparticles were shown to influence the amount of gases produced. As a result, this research is crucial in guaranteeing that traditional DGA techniques can be employed in transformers that use oil‐based nanofluids.

Investigation of electrical properties of developed indigenous natural ester liquid used as alternate to transformer insulation

<p>The <span>performance of every electrical system depends on the different electrical devices especially transformers. Petroleum-based mineral oil is widely used for insulation and cooling purpose. The disadvantage of mineral oil is its low biodegradability and is a major threat to the ecosystem due to its poor oxidative stability. To remedy the drawbacks, focus on alternative fluids that can replace traditional mineral oil. Alternative liquids such as natural esters are used which do not panic the ecosystem. With the support of additives in natural esters liquids, the productivity of the oil can be increased, paving the path for the green conversion of liquids in high voltage applications. The purpose of this article is to analyze the electrical properties of the newly developed indigenous oil. The inhibited oil was insulating oil to which antioxidants were added such as 2,6-ditertiary-butylparacresol, butylated hydroxyl anisole and tertiary butyl hydro qunine to slow down the oxidation rate and to check the electrical properties. This article discusses the electrical properties of mineral oil, developed indigenous oil with and without antioxidants as per IEC62770 standards. A 1.1 kVA transformer was then designed in a laboratory for load tests and Indigenous oil performance under load was evaluated.</span></p>

Effect of Molecular Structure on the Difference of Lightning Impulse Discharge Between Mineral Oil and Natural Ester Using DFT Calculation

The lighting impulse breakdown performance of natural ester (NE) is lower than that of the traditional mineral oil, which is a key point that needs to be considered in high-voltage level and large capacity transformers. The micromolecular structures of NE and mineral oil are quite different, which leads to significant differences in macroperformance. Therefore, molecular models of two types of oil were constructed in this article, and density functional theory (DFT) was used to calculate molecular microscopic parameters, such as ionization potential (IP) and polarization properties under the action of electric fields (EFs) with different directions. The results show that the IP of the NE is smaller than mineral oil, and the IP of the two oils continues to decrease with the increasing EFs, which is mainly because the highest occupied molecular orbital (HOMO) energy level of NE is significantly higher than that of mineral oil under EFs. Therefore, the lightning impulse breakdown voltage of NE will be lower than that of mineral oil, and the electron density difference (EDD) and atomic force of NE are greater than mineral oil under the EF; thus, the electronic structure of NE is more susceptible to EF. The differences of electronic structure between NE and mineral oil cause the discharge threshold of NE lower than that of mineral oil, which makes the discharge streamers in NE tend to develop along the axial direction of the electrode.

A review on transformer condition monitoring with critical investigation of mineral oil and alternate dielectric fluids

Transformers are very critical elements of modern power system network and have evolved in many ways over its long history. Transformers are most significant apparatus in interconnected power systems with consideration of several aspects like reliability, efficiency, economy, wide applications and operation. However mineral oil also called transformer oil is attracting more attention from researchers and transformer industry due to environmental concerns, limited stock, high price of petroleum resources and its disposal issues after getting contaminated. Above issues have motivated researchers to turn their attention to biodegradable and/or renewable insulating oil. Multiple facets, such as environmental requirements, safety and economic considerations, availability of technology and raw material governs the development of new insulating liquid materials. In addition, the increased equipment efficacy and the adoption of more environment friendly alternate dielectric fluids for power system solutions is gaining popularity towards steps to reduce the carbon footprint and achieving net zero cum decarbonisation global policy. This article provides the detailed review of transformer condition monitoring and the critical investigation about environment friendly dielectric fluids. They claim excellent lifecycle of the insulation, better working compatibility and improved performance compared to the traditional mineral oil base fluids in adherence of compliance, standards and graphical abstracts. These alternate dielectric fluids are getting proved as superior transformer fluids. The diverse investigational work carried out is incorporated, providing an overview of research. In addition, the future scopes, challenges and environment friendliness of various fluids are studied and deliberately articulated.

Spectroscopic determination of the synergistic effect of natural antioxidants in Bio-Transformer oils

Considering the eventual depletion of fossil fuels from which mineral oil transformer fluids are derived in addition to the environmental footprint associated with the use of the latter, vegetable oils are increasingly becoming formidable alternatives both as environmentally benign lubricants and as dielectric fluids. However, their lower oxidative stability and higher viscosity compared to traditional mineral oils are their main shortfalls. To address the lower oxidative stability problem, addition of synthetic antioxidants to vegetable oil transformer fluids has been found technically feasible, but given that these natural esters already have organo-soluble antioxidants, information about the concentrations of these phytochemicals is essential for a systematic approach to boosting oxidative stability. The presence of some of these in natural esters can lead to a synergy in antioxidation processes. In this paper, we have used Ultraviolet–Visible Spectroscopy and Infrared Spectroscopy to demonstrate the occurrence of natural antioxidants, alfa-tocopherol and beta-carotene, in concentrations sufficient to offer a synergistic effect in samples of transformer fluids from a producer. One major role of beta-carotene is quenching of reactive singlet oxygen species in the oxidation reaction chain when a photosensitizer is present. Therefore, our findings in this paper is a useful guide to planning a cost-effective means of producing a quality transformer fluid where the cost involved in mitigating photoinduced degradation of oil is a problem. Accordingly, the findings shed light on the quality of bio-oils used by the producer of the transformer fluids used in this study.

Analysis of AC breakdown strength of vegetable oils and effect of mineral oil

• AC breakdown strength of coconut oil is studied as against commercial soybean oil. • Analyzed the effect of aging (120 °C, 2 weeks) and mineral oil on AC breakdown strength. • AC breakdown data are statistically analyzed using Normal and Weibull distributions. • Aging or mineral oil reduces the withstand voltage, but the effect is less intense in coconut oil. • Coconut oil can be a potential replacement for traditional mineral oils. The effect of residual mineral oil on the AC breakdown strength of vegetable oil is widely studied to understand vegetable oil's reliability and dielectric integrity in retro-fitting a mineral oil-filled transformer. This paper describes the analysis of experimental results on two types of vegetable oil, namely –refined, bleached, and deodorized (RBD) coconut oil and commercial vegetable oil (MIDEL eN1215) derived from soybean oil seeds. The latter is also to act as a benchmark in analyzing the breakdown performance of RBD coconut oil, which is recently studied as a potential alternative to replace mineral oil from transformers located in tropical countries. The AC breakdown voltage tests were conducted using ASTM D1816 method at normal ambient conditions for both fresh and aged oils and considering 10 and 30% mineral oil in these vegetable oils. It is found that the distributions of breakdown voltages in RBD coconut oil, especially the lowest AC breakdown voltage, are similar to those of commercial vegetable oil for transformers. Therefore, from the viewpoint of AC withstand voltage, RBD coconut oil is equivalent to commercial vegetable oil under new conditions and even better under aged conditions or when mixed with mineral oil.

Investigation on Molecular Dynamics Simulation for Predicting Kinematic Viscosity of Natural Ester Insulating Oil

Natural ester insulating oil not only has a biodegradation rate of almost 100% but also meets the carbon emission requirements of China’s “Carbon Peak and Carbon Neutrality” and the “European Green Deal” proposed by the European Union. It is considered to be a good substitute for mineral insulating oil. However, due to its higher kinematic viscosity than traditional mineral oil in low-temperature environments, it limits the safety promotion and application of transformers in cold regions. First, we design an experiment to test the kinematic viscosity and density of natural ester insulating oil. Under extremely harsh experimental conditions, we measure key experimental data such as kinematic viscosity. Second, the structure of the four main triglyceride molecules is optimized, and the molecular dynamics (MD) simulation technology is used to establish an MD model that can predict the kinematic viscosity of natural ester insulating oil (−20 °C to 20 °C). Finally, the model is further simplified by the free volume theory to better predict the kinematic viscosity of natural ester insulating oil. This study makes up for the lack of laboratory low-temperature testing of the kinematic viscosity of natural ester insulating oil and provides a convenient and reliable tool for predicting the kinematic viscosity of natural ester insulating oil. It can not only predict the natural ester insulating oil mixed in various proportions but also predict the kinematic viscosity of a certain natural ester molecule. Furthermore, it also provides a guiding direction for the improvement of low-temperature kinematic viscosity of natural ester insulating oil, as well as a strong reference for predicting other properties of other substances.

Research and optimization of thermophysical properties of sic oil-based nanofluids for data center immersion cooling

Thermal management of high-power density equipment in data center is a key obstacle to power densification, and submerged cooling considered as an effective mean. Considering operability and economic factors, mineral oil is selected as the research object. In this study, the insulating silicon carbide oil based nanofluids are used as a new type of immersion cooling working fluid to replace the traditional mineral oil. The thermophysical properties of silicon carbide oil based nanofluids with wide concentration range from 0.1–10.3 vol% are characterized, and the optimal concentration of nanofluids are selected by Ansys Computational Fluid Dynamics finite volume method. Moreover, the heat transfer performance at Reynolds number of 250–3000 is analyzed. As a result, compared with the basic mineral oil, the heat transfer is significantly enhanced by silicon carbide based nanofluids. In particular, the enhanced effect cannot improve monotonously as the concentration increase. When the nanofluids are in the range of 0.3vol % and 3.7vol %, the maximum enhancements are 11.4% and 11.7% towards the basic fluid respectively. Last but not least, the 0.3 vol% nanofluids have better heat dissipation effect at low Reynolds number while 3.7 vol% nanofluids perform better at high Reynolds number. These results indicate that silicon carbide oil based nanofluids have a promising application in data center immersion cooling.

Molecular pyrolysis process and gas production characteristics of 3‐element mixed insulation oil under thermal fault

Mixed insulation oil is considered as a desired substitute for traditional mineral oil. A novel 3-element mixed insulation oil has been developed in our previous works, whose parameters satisfy the mineral oil standard (IEC 60296:2012). In the application of transformer oil, dissolved gas analysis is an effective method for insulation fault diagnosis. Thermal fault is a common and typical fault in transformers; however, the pyrolysis process and gas production characteristics of mixed insulation oil under thermal fault remain unknown. In this study, the pyrolysis process and gas production characteristics of 3-element mixed insulation oil have been studied through simulation and experiments, and mineral oil is equally treated for comparison. Results show that the gas production characteristics of mixed oil are closely related to its base oils, and 3-element mixed insulation oil generates more H2 and C2H6 under thermal fault, in which the percentage of H2 in the mixed oil is always three times that in the mineral oil. More CO2 is produced in mixed oil under thermal fault because of ester bonds; C2H4 is also a main characteristic gas for mixed insulation oil under thermal fault, and its proportion increases continuously with the increase of temperature. For mineral oil, the weight loss temperature in thermo-gravimetric (TG) curve corresponds to evaporation rather than decomposition. Natural esters have poor thermal stability according to simulation results, but they possess high flash point and weight loss temperature in the TG curve primarily because of their large average molecular weight.

Development of Bio-Cutting Fluid (Cirtullus lanatus) and its Performance Assessment on the Machining of AISI 1525 Steel Using Taguchi Technique and Grey Relational Analysis

Due to traditional mineral oils' adverse environmental and health effects, vegetable oil-based cutting fluids have become widely attractive in machining. The majority of the vegetable oils used in literature are edible and may compete with human consumption if promoted, thereby making it more expensive as cutting fluids. However, few studies have been carried out on the applicability of lesser-known vegetable oils as cutting fluids. This study, therefore, aims at investigating the efficiency of lesser-known vegetable oil (watermelon oil) as a machining cutting fluid. The developed watermelon oil was mechanically compared to the traditional mineral oil in turning AISI 1525 steel based on cutting temperature, surface roughness, and chip formation mode. The experiment depended on Taguchi plan with L9 orthogonal arrangement utilizing feed rate, depth of cut, and cutting speed as critical input parameters. Moreover, the grey relational analysis optimization approach was employed to analyze the parameter impacts and achieve the best possible cutting parameters. The optimization showed that the best combinations of cutting parameters for cutting speed, feed rate, and depth of cut were (355 rev/min, 0.1 mm/rev and 1 mm), and (355 rev/min, 0.1 mm/rev, and 1.25 mm) for watermelon and mineral oils, respectively.

Study of the Impregnation of Power-Transformer Cellulosic Materials With Dielectric Ester Oils

The application of alternative dielectric oils as esters in power transformers is hindered by the lack of knowledge regarding their properties and respecting which are the best techniques to ensure their proper performance. In this sense one of the fields needing an impulse is the impregnation processes of transformers cellulosic materials with these alternative oils, currently impregnated in most of the cases with mineral oils. This paper studies the impregnation behavior of eight usual dielectric solids, with two esters and a traditional mineral oil. Empirical equations of the impregnation evolution with time have been obtained, from these the rigid cellulosic materials present in the transformers and the viscosity of the dielectric oils have been identified as the key materials and properties to consider during impregnation. An adaptation of the current impregnation processes to the alternative oils have been proposed by increasing their temperature from ambient temperature up to 61-74°C, depending on the viscosity of the oil used.

Liquid dielectrics

The present Special Issue is devoted to papers, which deal with the subjects of liquid dielectrics. Most of the papers included in the present Special Issue are concerned with innovative insulating liquids belonging to the family of natural and synthetic esters. The large interest in ester liquids is due to their positive property to have a much higher flash points and fire points of over 300 °C, almost two times more than traditional mineral oils; in addition, natural esters are readily biodegradable and come from renewable resources, made out of seed crops, such as soybeans. In fact, scientific researches on advances related to these liquids are needed for the development of safer power transformers as essential part of the forthcoming announced green-economy, now no longer postponed for the benefit of our planet. The main validation points for these innovative liquids remain their dielectric behavior and their aging performance and for this reason outstanding researches are still going on. Other papers included in this Special Issue deal with important studies related to breakdown, partial discharge (PD) and the effort made worldwide to improve the liquid insulation properties through the use of innovative nanomaterial additives.