Dielectric fluid comprising natural biologically-derived oil with increased stability

Abstract

The present invention provides a dielectric fluid comprising an oil of natural biological origin and one or more compounds selected from the group consisting of phosphite compounds. It has been found that the addition of one or more compounds selected from the group consisting of phosphite compounds to a dielectric fluid comprising an oil imparts a stabilizing effect that reduces, inhibits, or prevents the formation of gaseous inclusions in the dielectric fluid during normal use.

Description

[0001] This application is a divisional application of patent application No. 201980028565.1 (PCT / US2019 / 023155), filed on October 27, 2020, with an application date of March 20, 2019, entitled "Dielectric Fluid Containing Naturally Biologically Derived Oil with Increased Stability". Technical Field

[0002] In one aspect, the present invention relates to dielectric fluid compositions for use in power distribution and power equipment, including insulating oil, the power distribution and power equipment including transformers, switching gears and cables. Background Technology

[0003] Dielectric (or insulating) fluids used in power distribution and power equipment (including transformers, switching gears, and cables) perform two important functions. These fluids act as electrical insulating media, exhibiting dielectric strength, and they transfer generated heat away from the equipment, acting as cooling media. For example, when used in transformers, dielectric fluids transfer heat from the windings and core of the transformer or connected circuitry to cooling surfaces. In addition to dielectric strength and cooling capacity, ideal dielectric fluids for electrical equipment also exhibit little or no adverse environmental impact, are compatible with the materials used to construct the equipment, and are relatively non-flammable.

[0004] Dielectric oils possess a number of specific functional properties. The dielectric breakdown, or dielectric strength, of an oil provides an indication of its resistance to electrical breakdown and is measured as the minimum voltage required to induce an arc discharge between two electrodes at a designated gap immersed in the oil. The pulse dielectric breakdown voltage provides an indication of the oil's resistance to electrical breakdown under transient voltage stresses such as lightning and surges. The dissipation factor of an oil is a measure of dielectric loss in the oil; a low dissipation factor indicates low dielectric loss and low concentrations of soluble polar contaminants. The outgassing tendency of an oil measures its tendency to release or absorb gases under conditions of partial discharge. Similarly, stray outgassing can occur due to thermal stress in dielectric oils (such as transformer oils), leading to the release of hydrogen, methane, ethane, ethylene, etc.

[0005] Since one of the functions of dielectric fluids is to carry and dissipate heat, factors that significantly affect a fluid's relative ability to function as a dielectric coolant include viscosity, specific heat, thermal conductivity, and coefficient of thermal expansion. When selecting a suitable dielectric fluid for a specific application, the values ​​of these properties must be weighed, especially over the full rated operating temperature range of the equipment.

[0006] In addition to the properties mentioned above that affect heat transfer, dielectric fluids should also possess relatively high dielectric strength, low dissipation factor, dielectric constant compatible with solid dielectrics, low tendency to release gas, and must be compatible with the materials of the electrical equipment they expose. Control of stray gas release prevents the accumulation of explosive gases in the overhead space of the electrical equipment.

[0007] Dielectric fluids containing vegetable oils or blends of vegetable oils and containing one or more antioxidant compounds for use in electrical equipment are described in U.S. Patent No. 7,651,641 to Corkran et al. Summary of the Invention

[0008] A typical practice in preparing dielectric fluids to reduce oxidative degradation effects is the addition of antioxidants based on di-tert-butylphenol. These antioxidants work by extracting hydrogen radicals from peroxides formed during oxidation and chelating these radicals. The resulting quinone methylates and stilbene are highly discolored, which is considered detrimental in certain dielectric fluid applications or where the color interferes with the visualization of oils. Furthermore, passivating agents such as aryltriazines have been added to dielectric fluids to reduce the catalytic effect of dissolved metals and metal surfaces on oxidative degradation, thereby extending the antioxidant's lifetime.

[0009] Oils used as dielectric fluids, such as mineral oils, synthetic esters, and especially bio-derived oils, have stability limitations when used as dielectric fluids. Thermal degradation is confirmed by the generation of stray gases selected from hydrogen, methane, ethane, and ethylene. Stray gases are measured according to ASTM D3612-02, Method C. Specifically, oxidative degradation increases the concentration of hydrogen and ethane in thermal degradation and is typically accompanied by the generation of organic acids, alcohols, and peroxides. Hydrogen and methane confirm ionization degradation caused by partial discharge (electron leakage), and arc discharge and electrostatic discharge are accompanied by the generation of hydrogen and acetylene.

[0010] It has been found that adding a phosphite component containing one or more phosphite compounds to an oil-containing dielectric fluid imparts a stabilizing effect that reduces, inhibits, or prevents the formation of stray gases in the dielectric fluid during normal use. Unbound by theory, it is believed that adding one or more compounds selected from the group consisting of phosphite compounds to a dielectric fluid imparts a stabilizing effect before the formation of peroxides, thereby advantageously preventing gas formation.

[0011] In one aspect, a dielectric fluid is provided comprising an oil and one or more compounds selected from the group consisting of phosphite compounds. In another aspect, a dielectric fluid is provided comprising an oil and one or more compounds selected from the group consisting of phosphite compounds, and further comprising a non-phosphite antioxidant component selected from one or more non-phosphite antioxidant compounds.

[0012] On one hand, there is provided a dielectric fluid formulated for use in power distribution or power equipment, the dielectric fluid comprising an oil and one or more compounds selected from the group consisting of phosphite compounds.

[0013] In one aspect, a method for insulating a power distribution or power unit is provided, the method comprising incorporating a dielectric fluid as described herein into the power distribution or power unit.

[0014] On the one hand, power distribution or power devices including dielectric fluids as described herein are provided. Detailed Implementation

[0015] The aspects of the invention described below are not intended to be exhaustive or to limit the invention to the exact forms disclosed in the detailed description below. Rather, the aspects chosen and described are intended to facilitate understanding and comprehension of the general principles and practice of the invention by way of illustration or example, thereby enabling others skilled in the art to grasp them.

[0016] On one hand, the dielectric fluid contains oil selected from the group consisting of: biologically derived oils, synthetic ester oils, mineral oils, and mixtures thereof.

[0017] In one aspect, the dielectric fluid contains biologically derived oil. For the purposes of this disclosure, biologically derived oil is oil derived from plant or animal sources. In one aspect, the biologically derived oil is refined, bleached, and deodorized (“RBD”) oil. In one aspect, the dielectric fluid contains at least 75% by weight of biologically derived oil. In one aspect, the dielectric fluid contains at least 85% by weight of biologically derived oil. In one aspect, the dielectric fluid contains at least 90% by weight of biologically derived oil. In one aspect, the dielectric fluid contains at least 95% by weight of biologically derived oil. In one aspect, the dielectric fluid contains at least 98% by weight of biologically derived oil. In one aspect, the only oil in the dielectric fluid is biologically derived oil.

[0018] Biologically derived oils are particularly desirable for use in the dielectric fluids of this invention because they are derived from renewable resources and are generally readily biodegradable. In one aspect, biologically derived oils offer the added benefit of increased paper stability in transformer applications. Unlike mineral oils, biologically derived oils provide the benefits of high flash point and ignition point characteristics, low flammability, and low flame propagation. The flash point, ignition point, and flammability of synthetic esters are highly composition-dependent. Under certain conditions, mineral oils are subjected to explosion and flame propagation, acting similarly to gasoline around an ignition source. Biologically derived oils with unsaturation provide beneficial flow properties, where reduced oil viscosity is associated with increased unsaturation.

[0019] On the one hand, oils in dielectric fluids are of natural biological origin, meaning they are derived from plant or animal sources that have not been modified by reactive chemistry (e.g., through transesterification or the formation of oil derivatives). For clarity, it should be understood that plant or animal oils modified by transesterification (i.e., the redistribution of the fatty acid fraction present in triglyceride oils onto their glycerol fractions) are considered of natural biological origin. Additionally, it should be understood that plant or animal oils obtained through extraction are considered of natural biological origin.

[0020] In one aspect, the dielectric fluid comprises vegetable oil. In another aspect, the dielectric fluid comprises vegetable oil selected from the group consisting of: castor oil, coconut oil, corn oil, cottonseed oil, crambie oil, flaxseed oil, jojoba oil, macadamia nut oil, resclero oil, sesame seed oil, olive oil, palm oil, peanut oil, pine nut oil, rapeseed oil, safflower oil, sunflower oil, soybean oil, and veronica oil, and mixtures thereof. In another aspect, the dielectric fluid contains only vegetable oil. In another aspect, the dielectric fluid contains only vegetable oil, selected from the group consisting of: castor oil, coconut oil, corn oil, cottonseed oil, crambie oil, flaxseed oil, jojoba oil, macadamia nut oil, resclero oil, sesame seed oil, olive oil, palm oil, peanut oil, pine nut oil, rapeseed oil, safflower oil, sunflower oil, soybean oil, and veronica oil, and mixtures thereof. On the one hand, the only oil in dielectric fluids is vegetable oil. On the other hand, dielectric fluids containing vegetable oils can provide commercially available oil compositions that are further modified by adding phosphite compounds. For example, Envirotemp FR3 is a natural ester fluid made from soybean oil and additives (di-tert-butylphenol antioxidants, pour point additives, dyes). Other similar fluids derived from renewable resources include Midel eN (based on rapeseed). These materials can be modified by adding phosphite compounds to reduce stray gas emissions.

[0021] On the one hand, dielectric fluids contain natural oils derived from microorganisms, algae, and similar organic sources.

[0022] In one case, the dielectric fluid contains animal fat. In another case, the only oil in the dielectric fluid is animal fat. Representative examples of animal fat include beef tallow, lard, fish oil, or chicken fat.

[0023] In one aspect, dielectric fluids include synthetic oils. In another aspect, synthetic oils are oils that are products of chemical reactions involving the formation of esters, aryl esters, C5-C12 saturated or unsaturated straight-chain and branched carboxylic acids, and mixtures thereof, by reacting polyols with saturated or unsaturated straight-chain and branched carboxylic acids, or by chemical modification of source oils through reaction chemistry (e.g., by transesterification or the formation of oil derivatives). Therefore, for the purposes of this discussion, oils obtained from plant or animal sources through chemical modification via transesterification are synthetic oils. In another aspect, dielectric fluids include synthetic oils prepared from reactants derived solely from plant or animal biological sources.

[0024] On one hand, the synthetic ester oil comprises a synthetic ester of a polyol selected from glycerol, pentaerythritol, trimethylolpropane (TMP), hydroxylated fatty acids, and polyglycerol. On another hand, the synthetic ester is formed by reacting a polyol with a compound selected from: C5-C25 saturated or unsaturated straight-chain and branched carboxylic acids; C5-C12 saturated or unsaturated straight-chain and branched carboxylic acids, aryl esters, C5-C12 saturated or unsaturated straight-chain and branched esters, C5-C25 saturated or unsaturated straight-chain and branched esters, and mixtures thereof.

[0025] In one aspect, the dielectric fluid comprises synthetic esters selected from the group consisting of: C5 to C24 branched and straight-chain aliphatic carboxylic acids with pentaerythritol, dipentaerythritol, 2,2-dimethylpropanediol, 2,2-dimethyl-3-isopropyl-1,3-propanediol, trimethylolpropane, glycerol, neopentyl glycol, 2,2-dimethylolbutane, trimethylolethane, sorbitol, (C2 to C12 diols) ethylene glycol, propylene glycol, 1,4-butanediol and 2-methylpropanediol, and mixtures thereof.

[0026] On one hand, the dielectric fluid comprises synthetic esters selected from the group consisting of esters of C5 to C24 branched and straight-chain aliphatic alcohols and acids, wherein the acid is selected from the group consisting of adipic acid, octanoic acid, azelaic acid, sebacic acid, phthalic acid, oxalic acid, glycolic acid, fumaric acid, and mixtures thereof.

[0027] On the one hand, the only oil in the dielectric fluid is synthetic oil.

[0028] In one aspect, the dielectric fluid comprises mineral oil. In another aspect, the dielectric fluid comprises mineral oil selected from the group consisting of straight-chain and branched aliphatic paraffinic hydrocarbons having a molecular weight of about 220 to about 700, or about 500 to about 700. In another aspect, the dielectric fluid comprises mineral oil having an ignition point of about 120°C to about 250°C, or having an ignition point of about 140°C to about 200°C. In another aspect, the dielectric fluid comprises mineral oil having an ignition point higher than 200°C. In another aspect, the dielectric fluid comprises mineral oil selected from the group consisting of cycloalkanes having similar properties and mixtures of the aforementioned paraffinic hydrocarbons and cycloalkanes, such as those described in U.S. Patent No. 4,082,866, the disclosure of which is incorporated herein by reference. In one aspect, the only oil in the dielectric fluid is mineral oil.

[0029] In one aspect, the dielectric fluid comprises a mixture of biologically derived oils and mineral oils. In another aspect, the dielectric fluid comprises a mixture of vegetable oils and mineral oils. In another aspect, the dielectric fluid comprises a mixture of synthetic ester oils and mineral oils. In another aspect, the dielectric fluid comprises a mixture of synthetic ester oils and biologically derived oils. In another aspect, the dielectric fluid comprises a mixture of synthetic ester oils, biologically derived oils, and mineral oils. In another aspect, the dielectric fluid comprises a mixture of synthetic ester oils, vegetable oils, and mineral oils.

[0030] It has been found that increased unsaturation and branching in oils are associated with increased stray gas emissions. In oils with significant amounts of unsaturation and branching, the addition of phosphite compounds to reduce stray gas emissions becomes more important. It should be noted that oils with relatively low or no unsaturation (e.g., with an iodine value less than 50) benefit greatly from the incorporation of phosphite compounds as described herein. However, oils with relatively high amounts of unsaturation benefit even more significantly from the addition of phosphite compounds to reduce stray gas emissions. In one aspect, the dielectric fluid contains oils with an IV of 50 to 200. In another aspect, the dielectric fluid contains oils with an IV of 80 to 200. In another aspect, the dielectric fluid contains oils with an IV of 100 to 200. In yet another aspect, the dielectric fluid contains oils with an IV of 110 to 200.

[0031] For the purposes of this disclosure, “iodine value” (IV) is defined as the number of grams of iodine that will react with 100 grams of the material being measured. Iodine value is a measure of the degree of unsaturation (carbon-carbon double and triple bonds) present in the material. Iodine value is recorded in grams of iodine (I₂) per 100 grams of material and is determined using the AOCS Cd Id-92 procedure.

[0032] On one hand, the dielectric fluid is free of organosilicon compounds, or free of phospholipids, or free of pigments, or free of lecithin, or free of fatty acids, or free of monoglycerides and diglycerides, or free of acids, or free of alcohols, or free of color impurities, or free of sulfur compounds, or free of cresols, or free of polycyclic aromatic hydrocarbons, or free of acids, or free of halogenated compounds, or free of amines. On another hand, the dielectric fluid contains oils of natural biological origin and is free of phospholipids, or free of pigments, or free of lecithin, or free of fatty acids, or free of monoglycerides and diglycerides. On another hand, the dielectric fluid contains synthetic ester oils and is free of acids, or free of alcohols, or free of color impurities. On another hand, the dielectric fluid contains mineral oils and is free of sulfur compounds, or free of cresols, or free of polycyclic aromatic hydrocarbons, or free of acids, or free of halogenated compounds, or free of amines.

[0033] In one aspect, the dielectric fluid contains highly purified oil. For the purposes of this disclosure, the oil is “highly purified” if it is treated on a clay medium (such as silicates, aluminates, etc.) to remove polar compounds and impurities, and then filtered to substantially remove particles that would be retained by a 1-micron filter. In another aspect, the dielectric fluid contains highly purified biologically derived oil.

[0034] It has been found that when selecting oils for use in dielectric fluids, it is advantageous for the oil to have a low initial peroxide value, thus avoiding undesirable side reactions and gas escape from the outset. Preferably, the peroxide value in transformer oils is kept low through degassing and maintaining an inert (nitrogen-sealed) headspace, allowing additives to be used for target oil maintenance during use, rather than for correcting oil conditions generated before they are introduced into application. As the dielectric fluid is exposed to atmospheric or oxidizing conditions over time, the peroxide value of the oil in the dielectric fluid can increase, for example, from a very low initial peroxide value of less than about 1 to a higher peroxide value of about 8 or 10 or even higher. Phosphite compounds have been found to be particularly effective in suppressing gas generation in dielectric fluids where the oil has an initial peroxide value of less than 5, or where the oil has an initial peroxide value of less than 3, or where the oil has an initial peroxide value of less than 2, or where the oil has an initial peroxide value of less than 1. On one hand, the oil used in the dielectric fluid has an initial peroxide value of about 0.01 to 5, or an initial peroxide value of about 0.01 to 3, or an initial peroxide value of about 0.01 to 2, or an initial peroxide value of about 0.01 to 1, or an initial peroxide value of about 0.1 to 1. For the purposes of this disclosure, "peroxide value" is determined by the AOCS method Cd 8b-90. However, it should be noted that dielectric fluids with high initial peroxide values ​​exhibit a reduction in stray gas emissions by adding phosphite compounds as described herein.

[0035] On one hand, the dielectric fluid comprises one or more compounds selected from the group consisting of phosphite compounds.

[0036] In one aspect, compared to similar dielectric fluid compositions without the phosphite component, the phosphite component is present in an amount sufficient to reduce hydrogen (H2) outgassing of the dielectric fluid as determined by dissolved gas analysis (ASTM D3612-02, Method C) by at least 60%. In another aspect, compared to similar dielectric fluid compositions without the phosphite component, the phosphite component is present in an amount sufficient to reduce H2 outgassing of the dielectric fluid as determined by dissolved gas analysis by at least 70%. In yet another aspect, compared to similar dielectric fluid compositions without the phosphite component, the phosphite component is present in an amount sufficient to reduce H2 outgassing of the dielectric fluid as determined by dissolved gas analysis by at least 80%.

[0037] In one aspect, compared to similar dielectric fluid compositions without the phosphite component, the phosphite component is present in an amount sufficient to reduce ethane outgassing of the dielectric fluid as determined by dissolved gas analysis (ASTM D3612-02, Method C) by at least 60%. In another aspect, compared to similar dielectric fluid compositions without the phosphite component, the phosphite component is present in an amount sufficient to reduce ethane outgassing of the dielectric fluid as determined by dissolved gas analysis by at least 70%. In yet another aspect, compared to similar dielectric fluid compositions without the phosphite component, the phosphite component is present in an amount sufficient to reduce ethane outgassing of the dielectric fluid as determined by dissolved gas analysis by at least 80%.

[0038] In one aspect, compared to similar dielectric fluid compositions without the phosphite component, the phosphite component is present in an amount sufficient to reduce methane outgassing of the dielectric fluid as determined by dissolved gas analysis (ASTM D3612-02, Method C) by at least 60%. In another aspect, compared to similar dielectric fluid compositions without the phosphite component, the phosphite component is present in an amount sufficient to reduce methane outgassing of the dielectric fluid as determined by dissolved gas analysis by at least 70%. In yet another aspect, compared to similar dielectric fluid compositions without the phosphite component, the phosphite component is present in an amount sufficient to reduce methane outgassing of the dielectric fluid as determined by dissolved gas analysis by at least 80%.

[0039] In one aspect, compared to similar dielectric fluid compositions without the phosphite component, the phosphite component is present in an amount sufficient to reduce ethylene outgassing of the dielectric fluid as determined by dissolved gas analysis (ASTM D3612-02, Method C) by at least 60%. In another aspect, compared to similar dielectric fluid compositions without the phosphite component, the phosphite component is present in an amount sufficient to reduce ethylene outgassing of the dielectric fluid as determined by dissolved gas analysis by at least 70%. In yet another aspect, compared to similar dielectric fluid compositions without the phosphite component, the phosphite component is present in an amount sufficient to reduce ethylene outgassing of the dielectric fluid as determined by dissolved gas analysis by at least 80%.

[0040] In one aspect, compared to similar dielectric fluid compositions without the phosphite component, the phosphite component is present in an amount sufficient to reduce hydrogen outgassing of the dielectric fluid as determined by dissolved gas analysis (ASTM D3612-02, Method C) by at least 60%, and additionally by reducing ethane outgassing of the dielectric fluid as determined by dissolved gas analysis (ASTM D3612-02, Method C) by at least 60%. In another aspect, compared to similar dielectric fluid compositions without the phosphite component, the phosphite component is present in an amount sufficient to reduce hydrogen outgassing of the dielectric fluid as determined by dissolved gas analysis by at least 70%, and additionally by reducing ethane outgassing of the dielectric fluid as determined by dissolved gas analysis by at least 70%. In yet another aspect, compared to similar dielectric fluid compositions without the phosphite component, the phosphite component is present in an amount sufficient to reduce hydrogen outgassing of the dielectric fluid as determined by dissolved gas analysis by at least 80%, and additionally by reducing ethane outgassing of the dielectric fluid as determined by dissolved gas analysis by at least 80%.

[0041] In one aspect, the phosphite component exists in a dielectric fluid at an amount from 0.05% to the solubility limit. In another aspect, the phosphite component exists in a dielectric fluid at an amount from 0.1% to the solubility limit. In one aspect, the phosphite component exists at an amount from 0.05% to 4% by weight. In another aspect, the phosphite component exists at an amount from 0.05% to 3% by weight. In another aspect, the phosphite component exists at an amount from 0.05% to 2% by weight. In another aspect, the phosphite component exists at an amount from 0.05% to 1.5% by weight. In another aspect, the phosphite component exists at an amount from 0.05% to 1% by weight. In another aspect, the phosphite component exists at an amount from 0.05% to 0.5% by weight. In another aspect, the phosphite component exists at an amount from 0.1% to 4% by weight. In another aspect, the phosphite component exists at an amount from 0.1% to 3% by weight. In one aspect, the phosphite component is present in an amount of 0.1% to 2% by weight. In another aspect, the phosphite component is present in an amount of 0.1% to 1.5% by weight. In another aspect, the phosphite component is present in an amount of 0.1% to 1% by weight. In another aspect, the phosphite component is present in an amount of 0.1% to 0.5% by weight.

[0042] In one aspect, the dielectric fluid comprises one or more compounds selected from the group consisting of water-stable phosphite compounds. For the purposes of this disclosure, a phosphite compound is defined as water-stable if a solid sample of a phosphite compound is placed in a chamber at 60°C and 85% relative humidity and a sample is taken to determine the percentage of hydrolysis over time, and the sample hydrolyzes no more than 30% within 80 minutes.

[0043] On one hand, the dielectric fluid comprises one or more compounds selected from the group consisting of phosphite compounds, which are selected from the group consisting of phosphite esters, triaryl phosphites, trialkyl phosphites, cyclic phosphites, pentaerythritol cyclic esters of diaryl phosphites, etc.

[0044] In one aspect, the phosphite component is selected from the group consisting of phosphite compounds or from phosphite compounds having one to three aryloxy groups. In another aspect, the phosphite component is selected from aryl phosphite compounds. In another aspect, the phosphite component is selected from triaryl phosphite compounds. In another aspect, the phosphite component is selected from the group consisting of phosphite compounds or from phosphite compounds that are cyclic esters and pentaerythritol cyclic bisaryl phosphites. In another aspect, the phosphite component is selected from the group consisting of cyclic aryl phosphites, cyclic alkyl-aryl phosphites, aryl cyclic phenoxy phosphites, bisaryl phosphites, alkylaryl phosphites, and mixtures thereof.

[0045] On one hand, the phosphite component is selected from the group consisting of: tris-(2,4-di-tert-butylphenyl)phosphite (commercially available, for example, as Irgafos 168); bis(2,4-dicumylphenyl pentaerythritol diphosphite) (commercially available, for example, as Doverphos S-9228); trinonylphenyl phosphite (commercially available, for example, as Adela ADK stabilizer 1178 or Doverphos 4); 1,3,7,9-tetra-tert-butyl-11-(2-ethylhexyloxy)-5H-benzo[d][1,3,2]-benzodioxane (commercially available, for example, as Amfine HP-10); 3,9-bis(2,6-di-tert-butyl-4-methylphenoxy)-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane (commercially available, for example, as Amfine HP-10). PEP-36A (commercially available); bis(2,4-di-tert-butylphenol) pentaerythritol diphosphite (commercially available as Irgafos 126); 4,4'-isopropylidene diphenol C12-15 alcohol phosphite (commercially available, for example, as Amfine 1500); 3,9-diphenoxy-2,4,8,10-tetraoxa-3,9-diphosspiro[5.5]undecane; 3,9-bis(octadecoxy)-2,4,8,10-tetraoxa-3,9-diphosspiro[5.5]undecane (commercially available, for example, as Amfine PEP-8); triphenyl phosphite (commercially available, for example, as Amfine TPP or Doverphos 10); isodecyl diphenyl phosphite (commercially available, for example, as Adela ADK stabilizer 135A or Doverphos). 8 (commercially available); phenyl diisodecyl phosphite (commercially available, for example, as Doverphos 7); diisodecyl pentaerythritol diphosphite (commercially available, for example, as Doverphos 1220); distearyl pentaerythritol diphosphite (commercially available, for example, as Doverphos S-680); trilauryl phosphite (commercially available, for example, as Doverphos 53); alkyl (C 12 -C 15 Bisphenol A phosphite (available, for example, as Doverphos 613); alkyl (C 10 Bisphenol A phosphite (available, for example, as Doverphos 675); 2-ethylhexyl diphenyl phosphite (available, for example, as Amfine C); 5,5-dimethyl-2-phenoxy-1,3,2-dioxophosphazene; methyl diphenyl phosphite; and mixtures thereof.

[0046] On one hand, the dielectric fluid containing the phosphite compound also contains a non-phosphite antioxidant component, which comprises one or more non-phosphite antioxidant compounds. It has been found that incorporating one or more non-phosphite antioxidant compounds into the dielectric fluid containing the phosphite compound supplements and further enhances the protection of the dielectric fluid against oxidative degradation. Additionally, compared to similar compositions without a non-phosphite antioxidant component, it has been found that incorporating one or more non-phosphite antioxidant compounds into the dielectric fluid containing the phosphite compound suppresses viscosity increases over time. On another hand, the presence of non-phosphite antioxidant components, and especially phenolic antioxidant compounds, has been found to contribute to oxidative stability in compositions exposed to oxygen. Therefore, on another hand, compositions containing both the phosphite component and the non-phosphite antioxidant component exhibit good stray gas suppression properties and oxidative stability, as determined by measuring the oxidation induction time (“OIT”) (measured at said temperature according to ASTM D6186–98). OIT tests were conducted at an air pressure of 500 + / - 25 psig and an airflow rate of 100 + / - 10 ml / min.

[0047] It is important to note that the presence of conventional antioxidants (non-phosphite antioxidant compounds, particularly phenolic antioxidants) does not prevent peroxide formation but rather serves to degrade peroxides after they have formed. Furthermore, the peroxide value of bio-derived oils with air in the headspace will increase over time. Oxidation can be reduced by replacing the oxygen atmosphere with an inert gas (such as nitrogen or argon) and by degassing the fluid. However, conventional antioxidants generally will not be effective in reducing peroxide accumulation at ambient temperatures. Increased temperature is effective in increasing the interaction between conventional antioxidants and peroxides, but it also increases the rate of thermal degradation of the oil. At approximately 120°C, the rate of peroxide degradation increases to exceed the rate of peroxide formation. In the presence of conventional antioxidants, alcohols are a byproduct of peroxide degradation. In the absence of antioxidants, peroxides degrade to form acids.

[0048] It has been observed that increased peroxide content also contributes to increased stray gas emissions. However, by using phosphite compounds as described herein, stray gas emissions resulting from degradation via peroxide formation, as well as this form of degradation, were significantly reduced.

[0049] When mineral oil is used, it has been found that peroxide formation and degradation in mineral oil-based dielectric compositions tend to accelerate at around 120°C. For this reason, heating the mineral oil-based dielectric composition is not a preferred method for controlling peroxides by interacting with conventional antioxidants in the composition.

[0050] In one aspect, the additional non-phosphite antioxidant component is selected from phenolic antioxidants, and in another aspect, it is a di-tert-butylphenol analog. In another aspect, the non-phosphite antioxidant component is selected from the group consisting of: butylated hydroxyanisole (BHA), butylated hydrogen toluene (BHT), tert-butylhydroquinone (TBHQ), tetrahydrobutyrophenone (THBP), ascorbyl palmitate (rosemary oil), propyl gallate, and α-tocopherol, β-tocopherol, or δ-tocopherol (vitamin E), and mixtures thereof.

[0051] On one hand, the additional non-phosphite antioxidant component is selected from the group consisting of: pentaerythritol tetra(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate) (commercially available, for example, as Iganox L101, Irganox 1010, BNX1010); hexamethylene bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (commercially available, for example, as Irganox L109); octadecyl-[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (commercially available, for example, as Irganox 1076); ethylene bis(oxyethylene) bis(3-(5-tert-butyl-4-hydroxym-tolyl)propionate) (commercially available, for example, as Irganox L109). 2,6-Di-tert-butyl-4-(4,6-bis(octylthio)-1,3,5-triazin-2-ylamino)phenol (available, for example, as Irganox 565); N,N'-hexane-1,6-di-di-bis(3,3,5-di-tert-butyl-4-hydroxyphenylpropionamide) (available, for example, as Irganox 1098); 4,6-bis(octylthiomethyl)o-cresol (available, for example, as Irganox 1520); 4,4'-methylene-bis-2,6-di-tert-butylphenol (available, for example, as Ethanox 4702); and 2,6-di-tert-butyl-4-methylphenol (BHT).

[0052] On the one hand, it has been found that, within certain ranges, the amount of phosphite component in the composition, the amount of non-phosphite antioxidant component in the composition, and the relative ratio of phosphite component to non-phosphite antioxidant component exhibit particularly superior properties in suppressing stray gas generation and controlling redox reactions. On the other hand, it has been found that incorporating excessive amounts of non-phosphite antioxidant component relative to the amount of phosphite component may adversely affect the suppression of stray gas generation.

[0053] In one aspect, the phosphite component is present in the dielectric fluid composition in an amount from about 0.05% by weight to the solubility limit of the phosphite component, and the non-phosphite antioxidant component is present in an amount such that the ratio of the phosphite component to the non-phosphite antioxidant component is 1 part of phosphite component to 0 to 1.2 parts of non-phosphite antioxidant component.

[0054] In one aspect, the phosphite component is present in the dielectric fluid composition in an amount from about 0.2% by weight to the solubility limit of the phosphite component, and the non-phosphite antioxidant component is present in an amount such that the ratio of the phosphite component to the non-phosphite antioxidant component is 1 part of phosphite component to 0 to 1.2 parts of non-phosphite antioxidant component.

[0055] On one hand, the phosphite component is present in an amount of about 0.2% by weight to about 1% by weight, and the non-phosphite antioxidant component is present in an amount such that the ratio of the phosphite component to the non-phosphite antioxidant component is 1 part of phosphite component to 0 to 1.2 parts of non-phosphite antioxidant component.

[0056] In one aspect, the phosphite component is present in the dielectric fluid composition in an amount from about 0.4% by weight to the solubility limit of the phosphite component, and the non-phosphite antioxidant component is present in an amount such that the ratio of the phosphite component to the non-phosphite antioxidant component is 1 part of phosphite component to 0 to 1.2 parts of non-phosphite antioxidant component.

[0057] On one hand, the phosphite component is present in an amount of about 0.4% to about 0.6% by weight, and the non-phosphite antioxidant component is present in an amount such that the ratio of the phosphite component to the non-phosphite antioxidant component is 1 part of phosphite component to 0 to 1.2 parts of non-phosphite antioxidant component.

[0058] On one hand, the phosphite component is present in the dielectric fluid composition at an amount from about 0.05% by weight to the solubility limit of the phosphite component, and the phosphite component is present in the dielectric fluid composition at an amount from about 0.05% by weight to the solubility limit of the non-phosphite antioxidant component; and further, provided that the ratio of the phosphite component to the non-phosphite antioxidant component is 1 part of phosphite component to 0 to 1.2 parts of non-phosphite antioxidant component.

[0059] On one hand, the phosphite component is present in the dielectric fluid composition at an amount from about 0.2% by weight to the solubility limit of the phosphite component, and the phosphite component is present in the dielectric fluid composition at an amount from about 0.05% by weight to the solubility limit of the non-phosphite antioxidant component; and further, provided that the ratio of the phosphite component to the non-phosphite antioxidant component is 1 part of phosphite component to 0 to 1.2 parts of non-phosphite antioxidant component.

[0060] In one aspect, the phosphite component is present in an amount of about 0.2% by weight to about 1% by weight, and the phosphite component is present in the dielectric fluid composition in an amount of about 0.05% by weight to the solubility limit of the non-phosphite antioxidant component; and further, provided that the ratio of the phosphite component to the non-phosphite antioxidant component is 1 part of phosphite component to 0 to 1.2 parts of non-phosphite antioxidant component.

[0061] On one hand, the phosphite component is present in the dielectric fluid composition at an amount from about 0.4% by weight to the solubility limit of the phosphite component, and the phosphite component is present in the dielectric fluid composition at an amount from about 0.05% by weight to the solubility limit of the non-phosphite antioxidant component; and further, provided that the ratio of the phosphite component to the non-phosphite antioxidant component is 1 part of phosphite component to 0 to 1.2 parts of non-phosphite antioxidant component.

[0062] In one aspect, the phosphite component is present in an amount of about 0.4% to about 0.6% by weight, and the phosphite component is present in the dielectric fluid composition in an amount of about 0.05% by weight to the solubility limit of the non-phosphite antioxidant component; and further, provided that the ratio of the phosphite component to the non-phosphite antioxidant component is 1 part of phosphite component to 0 to 1.2 parts of non-phosphite antioxidant component.

[0063] On one hand, the phosphite component is present in the dielectric fluid composition at an amount from about 0.4% by weight to the solubility limit of the phosphite component, and the phosphite component is present in the dielectric fluid composition at an amount from about 0.2% by weight to the solubility limit of the non-phosphite antioxidant component; and further, provided that the ratio of the phosphite component to the non-phosphite antioxidant component is 1 part of phosphite component to 0 to 1.2 parts of non-phosphite antioxidant component.

[0064] In one aspect, the phosphite component is present in an amount of about 0.4% to about 0.6% by weight, and the phosphite component is present in the dielectric fluid composition in an amount of about 0.2% by weight to the solubility limit of the non-phosphite antioxidant component; and further, provided that the ratio of the phosphite component to the non-phosphite antioxidant component is 1 part of phosphite component to 0 to 1.2 parts of non-phosphite antioxidant component.

[0065] On one hand, the phosphite component is present in the dielectric fluid composition at an amount from about 0.4% by weight to the solubility limit of the phosphite component, and the phosphite component is present in the dielectric fluid composition at an amount from about 0.3% by weight to the solubility limit of the non-phosphite antioxidant component; and further, provided that the ratio of the phosphite component to the non-phosphite antioxidant component is 1 part of phosphite component to 0 to 1.2 parts of non-phosphite antioxidant component.

[0066] In one aspect, the phosphite component is present in an amount of about 0.4% to about 0.6% by weight, and the phosphite component is present in the dielectric fluid composition in an amount of about 0.3% by weight to the solubility limit of the non-phosphite antioxidant component; and further, provided that the ratio of the phosphite component to the non-phosphite antioxidant component is 1 part of phosphite component to 0 to 1.2 parts of non-phosphite antioxidant component.

[0067] On the one hand, dielectric fluids also contain metal passivators. It has been found that the incorporation of metal passivators can be used in dielectric fluids, especially those containing synthetic ester oils. Without being bound by theory, metal passivators are believed to reduce the catalytic effect of dissolved metals and metal surfaces on oxidative degradation in the dielectric fluid's operating environment. Furthermore, dielectric fluid compositions containing additional metal passivators, as described herein, have been found to exhibit low fluid dissipation factors (and thus reduced electrostatic charging tendency) even under long-term oxidative stress conditions.

[0068] In one aspect, the metal passivating agent is selected from benzotriazole or its derivatives. In another aspect, the metal passivating agent is selected from N,N-bis(2-ethylhexyl)-arylmethyl-1H-benzotriazole-1-methylamine (commercially available, for example, as Irgamet 39); N,N-bis(2-ethylhexyl)-1H-1,2,4-triazole-1-methylamine (commercially available, for example, as Irgamet 30); 1H-benzotriazole (commercially available, for example, as Irgamet BTZ); methyl-1H-benzotriazole (commercially available, for example, as Irgamet TTZ); butyl-1H-benzotriazole; and 2,2'-[[(methyl-1H-benzotriazole-1-yl)methyl]imino]bis-ethanol (commercially available, for example, as Irgamet 42).

[0069] In one aspect, the metal passivating agent is present in an amount of about 0.001% to 2% by weight of the dielectric fluid. In another aspect, the metal passivating agent is present in an amount of about 0.005% to 1% by weight of the dielectric fluid. In yet another aspect, the metal passivating agent is present in an amount of about 0.005% to 0.4% by weight (i.e., 50 ppm to 4000 ppm) of the dielectric fluid.

[0070] In one aspect, when the dielectric fluid oil is a synthetic ester, the metal passivator is present in an amount sufficient to control the dissipation value of the dielectric fluid, as determined by IEC 60247 (120°C), to be equal to or less than 0.10 (10%) in a 164-hour oxidative stability test evaluated according to IEC 61125 Method C. In another aspect, when the dielectric fluid oil is a synthetic ester oil, the metal passivator is present in an amount sufficient to control the dissipation value of the dielectric fluid, as determined by IEC 60247 (120°C), to be equal to or less than 0.30 (30%) in a 164-hour oxidative stability test evaluated according to IEC 61125 Method C. In yet another aspect, when the dielectric fluid oil is a synthetic ester oil, the metal passivator is present in an amount sufficient to control the dissipation value of the dielectric fluid, as determined by IEC 60247 (120°C), to be equal to or less than 0.50 (50%) in a 164-hour oxidative stability test evaluated according to IEC 61125 Method C.

[0071] On the one hand, when the oil of the dielectric fluid is a synthetic ester, the metal passivator is present in an amount sufficient to control the dissipation value of the dielectric fluid, as determined by IEC 60247 (120°C), to be equal to or less than 0.30 (30%); or equal to or less than 0.60 (60%); or equal to or less than 0.90 (90%); or equal to or less than 1.0 (100%) in an 800-hour oxidative stability test as assessed according to IEC 61125 method C.

[0072] On the one hand, when the dielectric fluid oil is a synthetic ester oil, the metal passivator is present in an amount sufficient to control the dissipation value of the dielectric fluid, as determined by IEC 60247 (120°C), to be equal to or less than 0.60 (60%) in a 164-hour oxidative stability test as assessed according to IEC 61125 method C.

[0073] On the one hand, when the dielectric fluid oil is a synthetic ester oil, the metal passivator is present in an amount sufficient to control the dissipation value of the dielectric fluid, as determined by IEC 60247 (120°C), to be equal to or less than 0.90 (90%) in a 164-hour oxidative stability test as assessed according to IEC 61125 method C.

[0074] On the one hand, when the dielectric fluid oil is a synthetic ester oil, the metal passivator is present in an amount sufficient to control the dissipation value of the dielectric fluid, as determined by IEC 60247 (120°C), to be equal to or less than 1.0 (100%) in a 164-hour oxidative stability test evaluated according to IEC 61125 method C.

[0075] On the one hand, when the oil of the dielectric fluid is a biologically derived oil, the metal passivator is present in an amount sufficient to control the dissipation value of the dielectric fluid as determined by IEC 601125 (120°C) to be equal to or less than 0.50 (50%) in a 48-hour oxidative stability test evaluated according to IEC 61125 method C.

[0076] On the one hand, when the dielectric fluid is mineral oil, the metal passivator is present in an amount sufficient to control the dissipation value of the dielectric fluid, as determined by IEC 60247 (120°C), to be equal to or less than 0.50 (50%) in a 500-hour oxidation stability test as assessed according to IEC 61125 method C.

[0077] On the one hand, the oil's selected dielectric fluid components, phosphite compounds, optional non-phosphite antioxidant components, and optional metal passivators are chosen to provide the following specific physical properties:

[0078] On one hand, when the oil in the dielectric fluid is a biologically derived oil or a synthetic ester oil, the dielectric fluid has a flash point greater than 250°C as determined by ISO 2719. On the other hand, when the oil in the dielectric fluid is a biologically derived oil or a synthetic ester oil, the dielectric fluid has a flash point greater than 270°C as determined by ISO 2719. On the other hand, when the oil in the dielectric fluid is a mineral oil, the dielectric fluid has a flash point greater than 135°C as determined by ISO 2719.

[0079] On the one hand, dielectric fluids have an ignition point greater than 300°C, as determined by ISO 2592. On the other hand, dielectric fluids have an ignition point greater than 310°C, as determined by ISO 2592.

[0080] In one aspect, the dielectric fluid has a pour point of less than -5°C, as determined by ISO 3016. In another aspect, the dielectric fluid has a pour point of less than -10°C, as determined by ISO 3016. In yet another aspect, the dielectric fluid has a pour point of less than -20°C, as determined by ISO 3016.

[0081] In one aspect, the dielectric fluid has a pour point of less than -25°C, as determined by ISO 3016. In another aspect, the dielectric fluid has a pour point of less than -30°C, as determined by ISO 3016. In another aspect, the dielectric fluid has a pour point of less than -45°C, as determined by ISO 3016. In another aspect, when the oil of the dielectric fluid is a biologically derived oil or a synthetic ester oil, the dielectric fluid has a pour point of less than -10°C, as determined by ISO 3016. In another aspect, when the oil of the dielectric fluid contains soybean-based oil, the dielectric fluid has a pour point of less than -15°C, as determined by ISO 3016, or a pour point of less than -20°C, as determined by ISO 3016. In another aspect, when the oil of the dielectric fluid contains rapeseed oil, the dielectric fluid has a pour point of less than -30°C, as determined by ISO 3016. On the one hand, when the dielectric fluid is a synthetic ester oil, the dielectric fluid has a pour point of less than -45°C, as determined by ISO 3016. On the other hand, when the dielectric fluid is a mineral oil, the dielectric fluid has a pour point of less than -40°C, as determined by ISO 3016, or a pour point of less than -60°C, as determined by ISO 3016.

[0082] In one aspect, the dielectric fluid has a water content of less than 750 mg / kg, as determined by IEC 60814. In another aspect, the dielectric fluid has a water content of less than 200 mg / kg, as determined by IEC 60814. In another aspect, the dielectric fluid has a water content of less than 100 mg / kg, as determined by IEC 60814. In another aspect, the dielectric fluid has a water content of less than 60 mg / kg, as determined by IEC 60814. In another aspect, the dielectric fluid has a water content of less than 50 mg / kg, as determined by IEC 60814. In another aspect, the dielectric fluid has a water content of less than 30 mg / kg, as determined by IEC 60814. In another aspect, the dielectric fluid has a water content of less than 25 mg / kg, as determined by IEC 60814. In another aspect, the dielectric fluid has a water content of less than 20 mg / kg, as determined by IEC 60814. On the one hand, the dielectric fluid has a water content of about 5 mg / kg to 25 mg / kg, as determined by IEC 60814.

[0083] On the one hand, dielectric fluids have colors with a chromaticity of less than 200, as determined by ISO 2211.

[0084] On the one hand, the dielectric fluid exhibits a strength of less than 1000 kg / dm at 20°C. 3 The density, as determined by ISO 3675 and ISO 12185.

[0085] On the one hand, the dielectric fluid has a thickness of approximately 1 mm at 100°C. 2 / s to 15mm 2 kinematic viscosity / s, or approximately 1mm at 40°C. 2 / s to 35mm 2 kinematic viscosity / s, or approximately 20 mm at 40°C. 2 / s to 35mm 2 kinematic viscosity / s, or approximately 100 mm at -20°C. 2 / s to 3000mm 2 The kinematic viscosity is 3 μm / s, as determined by ISO 3104. On one hand, the dielectric fluid contains mineral oil and has a kinematic viscosity of approximately 3 mm at 40°C. 2 / s to 12mm 2 The kinematic viscosity is approximately 9 mm / s. On one hand, the dielectric fluid contains bio-derived oil and has a kinematic viscosity of approximately 9 mm / s at 40°C. 2 / s to 50mm 2 The kinematic viscosity is approximately 9 mm / s. On one hand, the dielectric fluid contains vegetable oil and has a kinematic viscosity of approximately 9 mm / s at 40°C. 2 / s to 50mm 2 The kinematic viscosity is approximately 7 mm / s. On one hand, the dielectric fluid contains synthetic oil and has a kinematic viscosity of approximately 7 mm at 40°C. 2 / s to 40mm 2 kinematic viscosity / s.

[0086] In one aspect, the dielectric fluid has an acidity of less than 0.06 mg KOH / g, as determined by AOCS method Cd-63. In another aspect, the dielectric fluid has an acidity of less than 0.03 mg KOH / g, as determined by AOCS method Cd-63. In another aspect, the dielectric fluid has an acidity of less than 0.02 mg KOH / g, as determined by AOCS method Cd-63. In yet another aspect, when the oil of the dielectric fluid is mineral oil, the dielectric fluid has an acidity of less than 0.01 mg KOH / g, as determined by AOCS method Cd-63.

[0087] In one aspect, the dielectric fluid has a breakdown voltage greater than or equal to 35 kV, as determined by IEC 60156. In another aspect, the dielectric fluid has a breakdown voltage greater than 45 kV, as determined by IEC 60156. In another aspect, the dielectric fluid has a breakdown voltage greater than 55 kV, as determined by IEC 60156. In another aspect, the dielectric fluid has a breakdown voltage greater than 65 kV, as determined by IEC 60156. In another aspect, the dielectric fluid has a breakdown voltage greater than 75 kV, as determined by IEC 60156. In another aspect, when the dielectric fluid oil is mineral oil, the dielectric fluid has a breakdown voltage greater than 30 kV, as determined by IEC 60156. In another aspect, when the dielectric fluid oil is mineral oil, the dielectric fluid has a breakdown voltage greater than 70 kV, as determined by IEC 60156.

[0088] On the one hand, the dielectric fluid has a DC resistivity greater than 2 GΩm at 90°C, as determined by IEC 60156. On the other hand, the dielectric fluid has a DC resistivity greater than 20 GΩm at 90°C, as determined by IEC 60156.

[0089] In one aspect, dielectric fluids are used in devices as electrical systems requiring electrical insulation and cooling. In another aspect, dielectric fluids are used to transfer heat from a point of generation and to insulate conductive elements (such as wire coils) from adjacent conductive elements. In another aspect, dielectric fluids are used in devices as electrical networks providing interconnection of electrical components, such as for computing, power distribution, power generation, or power conversion. In another aspect, dielectric fluids are used in devices comprising components selected from: capacitors, voltage regulators, voltage compensators, and phase shifters. In another aspect, dielectric fluids are used in devices selected from liquid-insulated electrical equipment such as electronic circuits and liquid-insulated electrical boards and panels. In another aspect, dielectric fluids are used in devices as switching gears. In another aspect, dielectric fluids are used in devices as data center computer modules. In another aspect, dielectric fluids are used in devices selected from transformers, the transformer comprising a housing, a core / coil assembly within the housing, wherein the dielectric fluid at least partially surrounds the core / coil assembly. In one aspect, dielectric fluids are used in devices selected from transformers, such as autotransformers, generator step-down and step-up transformers, interconnecting transformers, flexible AC transformers, distribution transformers (pole-mounted, base-mounted, dome / underground units, submersible, substation), phase-shifting transformers, electrostatic voltage compensators, HVDC transformers, furnaces and other industrial transformers, traction transformers, and grounding transformers. In another aspect, dielectric fluids are used in devices selected from reactors, battery packs, and battery systems.

[0090] In one aspect, a method of insulating a device as an electrical system requiring electrical insulation and cooling includes incorporating any of the dielectric materials described herein (including selected dielectric materials containing specifically specified materials or components or amounts of the dielectric materials described herein) into the device as an electrical system requiring electrical insulation and cooling. In another aspect, a method of insulating a device as an electrical network providing interconnection of electrical components, such as those for computing, power distribution, power generation, or power conversion. In another aspect, a method of insulating a device comprising components selected from: capacitors, voltage regulators, voltage compensators, and phase shifters. In another aspect, a method of insulating a device selected from liquid-insulated electrical equipment such as electronic circuits and liquid-insulated electrical boards and panels. In another aspect, a method of insulating a device as a data center computer module. In another aspect, a method of insulating a device selected from transformers, the transformer comprising a housing, a core / coil assembly within the housing, wherein a dielectric material at least partially surrounds the core / coil assembly. On one hand, methods for insulating devices selected from transformers, such as autotransformers, generator step-down and step-up transformers, interconnecting transformers, flexible AC transformers, distribution transformers (pole-mounted, base-mounted, dome / underground units, submersible, substation), phase-shifting transformers, electrostatic voltage compensators, HVDC transformers, furnaces and other industrial transformers, traction transformers, and grounding transformers. On the other hand, methods for insulating devices selected from reactors, battery banks, and battery systems.

[0091] On one hand, an apparatus is provided as an electrical system requiring electrical insulation and cooling, the apparatus comprising any of the dielectrics described herein (including selected dielectrics containing specifically specified materials or components or amounts of the dielectrics described herein).

[0092] On one hand, the device is selected from devices that include components selected from the following: capacitors, voltage regulators, voltage compensators, and phase shifters.

[0093] In one aspect, the device is selected from liquid-insulated electrical equipment such as electronic circuits and liquid-insulated electrical boards and panels. In another aspect, the device is a data center computer module. In another aspect, the device is selected from a transformer, which includes a housing, a core / coil assembly within the housing, wherein a dielectric fluid at least partially surrounds the core / coil assembly. In another aspect, the device is selected from transformers such as autotransformers, generator step-down and step-up transformers, interconnecting transformers, flexible AC transformers, distribution transformers (pole-mounted, base-mounted, dome / underground units, submersible, substation), phase-shifting transformers, electrostatic voltage compensators, HVDC transformers, furnaces and other industrial transformers, traction transformers, and grounding transformers. In another aspect, the device is selected from reactors, battery packs, and battery systems.

[0094] Example

[0095] program Unless otherwise specified, the test fluid used in these embodiments of the invention is untreated refined, bleached, and deodorized (“RBD”) soybean oil (“SBO”), treated with 0.5% by weight of a reagent for evaluation in stray gas testing. If reagent dissolution is required, the fluid is heated under nitrogen. The treated fluid is drawn into a 50 mL syringe, capped to prevent fluid loss and air introduction, and placed in an oven at 80°C or 120°C for 48 hours. The syringe is removed from the oven to cool. The dissolved gases in the fluid are then tested according to ASTM Method D-3612 to determine the level of stray gas.

[0096] Example 1: Comparison of RBD-SBO fluid (Irgafos 168) containing 0.5% phosphite with control sample .

[0097] The test results for determining the venting level are presented in Table 1 below:

[0098] Table 1

[0099]

[0100] Irgafos 168 = tris-(2,4-di-tert-butylphenyl)phosphite

[0101] Results Discussion :

[0102] At 80°C, hydrogen and ethane were identified as the two gases indicative of thermally induced stray gas degradation. Compared to the control, a significant reduction in stray gas release of both gases was observed in RBD-SBO fluids containing phosphites.

[0103] Example 2: RBD-SBO dielectric fluid, RBD-SBO dielectric fluid containing phosphite compounds, and RBD-SBO dielectric fluid containing non-phosphite compounds. Comparison of RBD-SBO dielectric fluids of phosphate antioxidants .

[0104] All non-control compositions contain 0.5% by weight of the specified additive (phosphite compound or non-phosphite antioxidant). The RBD-SBO dielectric fluid of this embodiment has a peroxide value of 10.

[0105] The test results for determining the venting level are presented in Table 2 below:

[0106] Table 2

[0107]

[0108] Discussion of Results:

[0109] Compared to dielectrics containing non-phosphite antioxidants, dielectrics containing phosphite compounds (sample B) significantly reduced stray outgassing of both hydrogen and ethane. Notably, compared to similar compositions without metal passivators, phenol-based antioxidants containing metal passivators (i.e., di-tert-butylphenol benzotriazole with additional metal surface inhibition function – samples D, E, F, I, L, M, and N) actually exhibited increased stray outgassing.

[0110] Generally, phosphites are considered minor antioxidants with significantly lower antioxidant strength compared to di-tert-butylphenol-based antioxidants. Comparisons with other classes of antioxidants suggest that the effects of phosphites extend beyond antioxidant activity. Together with the differences in oxidative stability results, this indicates that the mechanism of action in suppressing stray gas may be based on mechanisms other than antioxidant properties. Without being bound by theory, stray gas is believed to be a result of thermally induced free radical degradation. Therefore, phosphites are effectively suppressing stray gas mechanisms. The removal of peroxides is expected to lead to some degree of stray gas reduction. Non-phosphite materials do not effectively reduce either gas, and some materials increase the tendency for oil to release gas.

[0111] Example 3: RBD-SBO low peroxide value dielectric fluid, RBD-SBO low peroxide value containing phosphite compounds Comparison of low peroxide value dielectric fluids and RBD-SBO low peroxide value dielectric fluids containing non-phosphite compound antioxidants .

[0112] The non-control compositions all contain 0.5% by weight of the specified additives (phosphite compounds, non-phosphite antioxidants, or other additive types). The RBD-SBO dielectric fluid of this example has a peroxide value of 0.6.

[0113] The test results for determining the venting level are presented in Table 3 below:

[0114] Table 3

[0115]

[0116] 1 Incorporate to the solubility limit, which is less than 0.5% by weight.

[0117] Results Discussion :

[0118] Compared to dielectrics containing non-phosphite antioxidants, dielectrics containing phosphite compounds (sample BJ) significantly reduced the outgassing of both hydrogen and ethane. Sample K showed increased hydrogen outgassing but decreased ethane outgassing. However, these data are based on only a single experimental run, and it is believed that the integrity of the phosphite sample may have been compromised.

[0119] In contrast, low-peroxide-value dielectric fluids containing di-tert-butylphenol antioxidants or other types of additives increased both hydrogen and ethane outgassing. This test confirmed that the incorporation of phosphite compounds prevented outgassing in dielectric fluids when other additives did not prevent it in similar dielectric fluids without phosphite components.

[0120] In all subsequent embodiments, the RBD—refined, bleached, and deodorized vegetable or synthetic ester oil—was purified by clay treatment prior to use to obtain a dielectric fluid. Stray gas tests were performed by holding the air-saturated oil in an oven at 80°C or 120°C for 48 or 168 hours, as indicated.

[0121] Example 4: Compared with other stabilizers, antioxidants, and passivators, phosphites showed better performance at 80°C (48-hour test). Effectiveness in controlling stray gas release

[0122] Table 4 illustrates how RBD soybean oil heated to 80°C for 48 hours was affected by various additives. The primary indicators were hydrogen and ethane. In these examples, the levels of other gases were not significant. Sample 4-1 was RBD-SBO without additives and heat treatment to compare the baseline levels of stray gases, analyzed by dissolved gas analysis (DGA). Sample 4-2 was RBD-SBO without additives after heat treatment. Among all categories of antioxidants tested, phosphite compounds showed a significant reduction in both stray gases. Other examples showed no significant change or increase in any one or both stray gases.

[0123] Table 4: Initial data demonstrate that phosphites are more effective than other stabilizers, antioxidants, passivators, etc., in controlling stray gas emissions at 80°C (48-hour test). RBD-SBO is used in conjunction with 0.5% by weight of additives.

[0124]

[0125] The data clearly demonstrate that butylated phenol antioxidants do not control stray gas release, but can contribute to a significant increase in stray gas release in bio-derived oils. Passivating compound compounds (which are typically benzotriazole compounds (Examples 4-10, 4-12, and 4-15)) also significantly increase stray gas release in bio-derived oils.

[0126] Example 5: Negative Interactions between Butylphenol, Irganox L101, and Passivating Agent

[0127] Table 5 shows the interaction between Irganox L101 (butylated phenol), one of the most common antioxidants used in transformer oils, and Irgamet 39, a common passivator, compared to or in combination with the phosphite compound Irgaphos 168.

[0128] Table 5: Negative interactions of butylated phenol, Irganox L101 and passivator Irgamet 39 against the compensating effect of Irgaphos 168 phosphite on the control of stray outgassing in RBD-SBO at 80 °C for 48 hours.

[0129]

[0130] A comparison of samples 5-16 and 5-17 shows that incorporating conventional butylated phenol increases stray gas emissions by 370%, exceeding that of purified soybean oil. In contrast, a comparison of samples 5-16 and 5-18 shows a significant reduction in stray gas emissions through the use of phosphite compounds, even lowering the levels to below those of purified untreated oil. Samples 5-19 and 5-20 demonstrate that phosphite compounds even reverse the stray gas emission effect of butylated phenol. Samples 5-20, 5-21, and 5-22 illustrate the adverse effects of passivating agents on oil, where small amounts of passivating agent have a severely detrimental effect on stray gas emissions. Samples 5-24 through 5-28 demonstrate how the Irgaphos 168 phosphite compound overcomes the stray gas emission effect of the combination of butylated phenol antioxidant and benzotriazole passivating agent.

[0131] Example 6: Effects of typical antioxidants on increasing stray gases

[0132] Typical antioxidants exhibit the following general behavior in increasing stray gases: Table 6. These compounds are classified as butylated phenol, di-tert-butylphenol thiothiazide, di-tert-butylphenol thiol, di-tert-butylphenol benzotriazine, aminotriazole, benzalkonium chloride, thiol diester, piperidinyl ester - N-alkoxide piperidinyl ester.

[0133] Table 6: Increase of stray gas in RBD-SBO by using 0.5% by weight antioxidant at 80°C for 48 hours.

[0134]

[0135] Example 7: Reducing stray gas release in oil through phosphite compounds

[0136] The screening of phosphite compounds demonstrated the general ability of these compounds to reduce stray gas emissions in oil.

[0137] Table 7 shows the benefits of treating purified, refined, bleached, and deodorized soybean oil with 0.5% of the listed phosphites, followed by heating at 80°C for 48 hours in a sealed container, and then testing the dissolved gases in the oil.

[0138] Table 7: Screening of phosphite compounds to reduce stray gas release in RBD-SBO at 80°C for 48 hours.

[0139]

[0140] Example 8: Butylphenol and phosphorous acid in highly purified RBD-SBO for 18 hours at 80°C and 120°C Comparison of salt compounds

[0141] Stray outgassing of highly purified RBD-SBO containing butylated phenol Irganox L101 or the phosphite compound Irgaphos 168 was compared when the oil was kept at 80°C or 120°C for 18 hours. The results are shown in Table 8.

[0142] Table 8: Comparison of stray gas releases from highly purified RBD-SBO containing butylated phenol or phosphite compounds

[0143] Sample number Temperature ℃ Irgaphos 168% by weight Irganox L101 weight % hydrogen ppm ethane ppm 8-1 80 0 0.4 43 95 8-2 80 0.4 0 6 8 8-3 120 0 0.4 44 347 8-4 120 0.4 0 30 85

[0144] Example 9: Aliphatic synthetic ester compositions comprising various levels of benzotriazole passivating agent and phosphite Assessment of vented gases.

[0145] It is known that temperatures of 120°C can accelerate the degradation of both natural and synthetic esters. This was confirmed in oven tests at 80°C with untreated mineral oil and synthetic esters, demonstrating the higher stability of aliphatic base oils without stray gas release. Increased stability of aliphatic compounds requires temperatures above 100°C to increase the rate of stray gas release. Samples were tested at 120°C for 48 and 168 hours. Table 9A shows the results after heat treatment at 120°C for 48 hours.

[0146] Table 9A: Stray gas release of aliphatic synthetic esters at 120°C for 48 hours and the stabilizing effect of Irgaphos 168 phosphite.

[0147]

[0148] Commercially synthesized ester sample Midel 7131, known to have undetermined levels of Irganox L101 and a passivator, exhibited high levels of stray outgassing over a shorter time period than the synthetic ester fluid used in this study. At elevated temperatures where butylated phenol is known to act more rapidly on peroxide-induced stray outgassing (compare samples 9-29 and 9-30), the benzotriazole passivator showed an effect that overcame any effect of butylated phenol and significantly increased hydrogen stray gas (sample 9-31). The phosphite compound Irgaphos 168 significantly reduced hydrogen stray gas outgassing in the synthetic esters of samples 9-32 and 9-33.

[0149] The superiority of phosphite compounds in controlling stray gas release over other additive challenges was demonstrated by increasing the severity of exposure to 168 hours at 120°C (Table 9B).

[0150] Table 9B: Stray gas release of aliphatic synthetic esters at 120°C for 168 hours and the stabilizing effect of Irgaphos 168 phosphite.

[0151]

[0152] Example 10: Proof that Irgaphos 168 phosphite compound prevents stray gas release in mineral oil .

[0153] Mineral oil is known to degrade at 120°C. Table 10 shows the high stray gas rates in mineral oil fluids without additives, and the ability of phosphite compounds to prevent stray gas emissions.

[0154] Table 10: Evidence that Irgaphos 168 phosphite compounds prevent stray gas release in mineral oils.

[0155] Sample number Irgaphos 168% by weight hydrogen ppm methane ppm ethane ppm ethylene ppm 10-39 0 31 444 413 14 10-40 0.4 <2 4 <1 2

[0156] Example 11: Oxidative stability test results of RBD-SBO with and without phosphite and passivating agent

[0157] Oxidative stability tests of soybean oil formulations (Table 11) indicate that Irgaphos 168 can be used in formulations with improved total acidity (specification <0.3% total). However, it has been found that using passivating agents with bio-derived oils significantly increases the viscosity and acidity of the fluid. For aliphatic synthetic esters, passivating agents do not affect viscosity but have an adverse effect on the acidity and dissipation factor (tanδ) of the fluid, as shown in Table 12.

[0158] Table 11: Results of oxidative stability test of RBD-SBO (IEC 61125 Method C, 48 hours, 120℃, 2.5 mL / min gas flow).

[0159]

[0160]

[0161] Example 12: Results of oxidative stability tests on aliphatic synthetic esters

[0162] Aliphatic synthetic ester fluids formulated with Irgaphos 168 phosphite compounds exhibited excellent properties in oxidative stability tests. When using Irgaphos 168, the viscosity remained constant, and the test results after 800 hours of oxidative stability testing at 120°C and 2.50 mL / min air flow rate, according to IEC 61125 Method C, exceeded the specifications required for the 164-hour test. The results are summarized in Table 12.

[0163] Table 12: Results of oxidative stability tests on aliphatic synthetic esters (IEC 61125 Method C, 120℃, 2.5 mL / min) Airflow rate (specified time period: 164 hours or 800 hours) .

[0164]

[0165] Note: Viscosity changes were <1.0% by weight in all cases, and <0.01% by weight for slurry.

[0166] Example 13: Reduction of stray gas release in natural oils with high peroxide values

[0167] Oils with high initial peroxide content also exhibited increased stray gas emissions, as seen in Table 13. However, this stray gas emission was significantly reduced by using the Irgaphos 168 phosphite compound. It should be noted that the presence of conventional antioxidants (non-phosphite antioxidant components) does not prevent peroxide formation but rather serves to degrade peroxides after their formation. However, conventional antioxidants will not effectively reduce peroxide accumulation at ambient temperatures. Increased temperature is effective in increasing the interaction between conventional antioxidants and peroxides, but it also increases the thermal degradation rate of the oil.

[0168] Table 13: Effects of high peroxide value oils and Irganox 168 on reducing stray gas emissions (48 hours, 80°C) .

[0169]

[0170] Example 14: Reduction of stray gas release in natural oils with low peroxide content

[0171] Experiments were conducted to demonstrate the reduction of stray gas release in natural oils without high peroxide content. The test results are provided in Tables 14-1 and 14-2.

[0172] Table 14-1: Effects of Irganox 168 on reducing stray gas emissions in bio-derived oils at 80°C for 48 hours efficacy .

[0173]

[0174] Table 14-2; Examples of phosphite compounds (triphenyl phosphite) maintained at 80°C for 48 hours in various oils.

[0175]

[0176] Example 15: Confirmation that phosphites in the oil do not interfere with transformer testing

[0177] Importantly, phosphite compounds do not interfere with the transformer's diagnostic testing, where acetylene levels are used to determine whether an arc discharge or discharge condition is occurring. To test this, the oil was subjected to discharges greater than 65kV and 50kV, which were passed through a 2mm gap into 350mL of oil to demonstrate that there was no difference in acetylene and DGA levels. It should be noted that the oil was not heat-treated, therefore, no additional stray gases are expected to be generated except for any substances passing through the oil via sparks.

[0178] Table 15: Confirmation of the non-interference effect of the phosphite compound Irgaphos 168 on the discharge diagnosis of biologically derived oil (RBD-SBO).

[0179]

[0180] As used herein, the term “about” or “approximately” means within an acceptable range for a particular parameter, determined by those skilled in the art, which depends in part on how the value was measured or determined, for example, limitations of the sample preparation and measurement system. Examples of such limitations include sample preparation in wet / dry environments, different instruments, variations in sample height, and different requirements for signal-to-noise ratio. For example, “about” may mean 1 / 10 greater or less than the specified value or range, but is not intended to limit any value or range to only that broader definition. For example, a concentration value of about 30% means a concentration between 27% and 33%. Each value or range preceded by the term “about” is also intended to cover embodiments of the specified absolute value or range. Alternatively, particularly relative to measurements on logarithmic scales, such as those seen in biological systems or processes, the term may mean within the order of magnitude of the value, preferably within 5 times, more preferably within 2 times.

[0181] Throughout this specification and claims, unless the context otherwise requires, the words “comprising” and variations (e.g., “including” and “containing”) should be understood to imply inclusion of the specified integer or step or group of integers or steps, but do not exclude any other integer or step or group of integers or steps. When used herein, “consisting of” excludes any element, step, or component not specified in the elements of the claim. When used herein, “substantially constitutes” does not exclude materials or steps that do not substantially affect the basis and novelty of the claim. In the various embodiments of the invention, any of the terms “comprising,” “substantially constitutes,” and “consisting of” used in the description of the embodiments may be replaced by any of the other two terms.

[0182] For all purposes, all patents, patent applications (including provisional applications), and publications cited herein are incorporated by reference as if individually incorporated. Unless otherwise specified, all parts and percentages are by weight, and all molecular weights are weight-average molecular weights. The above detailed description is given only for clarity of understanding. It should be understood that no unnecessary limitations are intended. The invention is not limited to the exact details shown and described, as variations that will be apparent to those skilled in the art will be included within the scope of the invention as defined by the claims.

Claims

1. A dielectric fluid for reducing stray gas release, the dielectric fluid comprising: Vegetable oil, wherein the vegetable oil is selected from rapeseed oil, sunflower oil, soybean oil, and mixtures thereof; A phosphite component comprising one or more phosphite compounds, said phosphite component being selected from phosphite compounds having one to three aryloxy groups; and Phenolic antioxidant components, The phosphite component is present in an amount of 0.1% to 1.0% by weight, and compared to a dielectric fluid composition without the phosphite component, the phosphite component is present in an amount sufficient to reduce stray gas emissions of the dielectric fluid as determined by dissolved gas analysis by at least 60%, wherein the stray gas is H2, ethane, methane, or ethylene, and wherein the dielectric fluid has a breakdown voltage of at least 45 kV as determined according to IEC 60156. The dissolved gas analysis was performed according to ASTM D3612-02, Method C.

2. The dielectric fluid according to claim 1, wherein the rapeseed oil includes high oleic acid and low erucic acid rapeseed oil, US low erucic acid rapeseed oil, and EU rapeseed oil.

3. The dielectric fluid according to claim 1, wherein the phosphite component is present in an amount of 0.1% to 0.5% by weight.

4. The dielectric fluid according to claim 1, wherein the phosphite component comprises three aryloxy groups.

5. The dielectric fluid according to claim 1, wherein the phenolic antioxidant component is selected from the group consisting of: butylated hydroxyanisole; butylated hydrogen toluene; tert-butylhydroquinone; tetrahydrobutyrophenone; propyl gallate; α-tocopherol, β-tocopherol or δ-tocopherol; and mixtures thereof.

6. The dielectric fluid according to claim 1, wherein the phenolic antioxidant component is selected from the group consisting of: pentaerythritol tetra(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate); hexamethylene bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]; octadecyl-[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]; ethylene bis(oxyethylene) bis-(3-(5-tert-butyl- 4-Hydroxym-tolyl)propionate; 2,6-di-tert-butyl-4-(4,6-bis(octylthio)-1,3,5-triazin-2-ylamino)phenol; N,N'-hexane-1,6-di-di-bis(3-3,5-di-tert-butyl-4-hydroxyphenylpropionamide); 4,6-bis(octylthiomethyl)o-cresol; 4,4'-methylene-bis-2,6-di-tert-butylphenol; and 2,6-di-tert-butyl-4-methylphenol.

7. The dielectric fluid according to claim 1, wherein the dielectric fluid comprises vegetable oil selected from soybean oil, high oleic acid and low erucic acid rapeseed oil, sunflower oil, and mixtures thereof.

8. The dielectric fluid of claim 1, wherein the dielectric fluid comprises vegetable oil selected from soybean oil, U.S. low-erucic acid rapeseed oil, and mixtures thereof.

9. The dielectric fluid according to claim 1, wherein the dielectric fluid comprises a vegetable oil having an iodine value of 50 to 200.

10. The dielectric fluid according to claim 1, wherein the dielectric fluid has a peroxide value of less than 5.

11. The dielectric fluid according to claim 1, wherein the dielectric fluid has a peroxide value of less than 3.

12. The dielectric fluid according to claim 1, wherein the dielectric fluid has a peroxide value of less than 2.

13. The dielectric fluid according to claim 1, wherein the dielectric fluid has a peroxide value of less than 1.

14. The dielectric fluid according to claim 1, wherein the dielectric fluid has a peroxide value of 0.01 to 5.

15. The dielectric fluid according to claim 1, wherein the dielectric fluid has a peroxide value of 0.01 to 3.

16. The dielectric fluid of claim 1, wherein the dielectric fluid has a peroxide value of 0.01 to 2.

17. The dielectric fluid of claim 1, wherein the dielectric fluid has a peroxide value of 0.01 to 1.

18. The dielectric fluid of claim 1, wherein the dielectric fluid has a peroxide value of 0.1 to 1.

19. A dielectric fluid formulated for reducing stray gas emissions in power distribution or power equipment, the dielectric fluid comprising: Vegetable oil, wherein the vegetable oil is selected from rapeseed oil, sunflower oil, soybean oil, and mixtures thereof; A phosphite component comprising one or more phosphite compounds, said phosphite component being selected from phosphite compounds having one to three aryloxy groups; and Phenolic antioxidant components, The phosphite component is present in an amount of 0.1% to 1.0% by weight, and compared to a dielectric fluid composition without the phosphite component, the phosphite component is present in an amount sufficient to reduce stray gas emissions of the dielectric fluid as determined by dissolved gas analysis by at least 60%, wherein the stray gas is H2, ethane, methane, or ethylene, and wherein the dielectric fluid has a breakdown voltage of at least 45 kV as determined according to IEC 60156. The dissolved gas analysis was performed according to ASTM D3612-02, Method C.

20. The dielectric fluid of claim 19, wherein the rapeseed oil includes high oleic acid and low erucic acid rapeseed oil, U.S. low erucic acid rapeseed oil, and EU rapeseed oil.

21. The dielectric fluid of claim 19, wherein the phosphite component is present in an amount of 0.1% to 0.5% by weight.

22. The dielectric fluid of claim 19, wherein the dielectric fluid comprises vegetable oil selected from soybean oil, high-oleic-low-erucic acid rapeseed oil, American low-erucic acid rapeseed oil, sunflower oil, and mixtures thereof.

23. The dielectric fluid according to claim 1 or 19, wherein the dielectric fluid comprises vegetable oil selected from soybean oil, rapeseed oil, and mixtures thereof.

24. The dielectric fluid according to any one of claims 1-2, 4-20, and 22, wherein the phosphite component is present in an amount of 0.1% to 0.5% by weight, and the phosphite component is present in an amount sufficient to reduce stray gas emissions of the dielectric fluid as determined by dissolved gas analysis by at least 60% compared to a dielectric fluid composition not containing the phosphite component, wherein the stray gas is H2. The dissolved gas analysis was performed according to ASTM D3612-02, Method C.

25. A power distribution or power supply device, the power distribution or power supply device comprising a dielectric fluid according to any one of claims 1 to 24.

26. The power distribution or power supply device according to claim 25, wherein the device is selected from capacitors and transformers.

27. The power distribution or power device according to claim 25, wherein the device is a transformer.

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