NO20093475L - Dielectric fluid composition with vegetable oil - Google Patents

Abstract

There is disclosed an electrical device having therein a dielectric fluid composition, wherein the dielectric fluid composition includes at least one refined bleached vegetable oil where the odor is removed, and at least one antioxidant, wherein the dielectric fluid composition has a pour point of less than ca. 20 ° C measured with either ASTM D97 or ASTM D5950.

Description

The present description relates to dielectric fluids for use in electrical devices.

Dielectric (or insulating) fluid compositions used in electrical distribution and power expression act as an electrically insulating medium, i.e. they exhibit dielectric strength and they transport generated heat away from the equipment, i.e. act as a cooling medium. When used in a transformer transports e.g. dielectric fluids heat from the windings and core of the transformer or coupled circuits to cooling surfaces.

Liquid-filled electrical appliances used in certain climates may require a dielectric fluid composition that maintains its electrical and physical properties, particularly pourability, for extended periods at low temperatures. This pourability requirement has a limited area for the use of vegetable oil-based dielectric fluid compositions, which typically have pour points above approx. -10°C.

Since some electrical devices use large quantities of dielectric fluid, and that the dielectric fluid can remain in the device over extended periods of time, there is a possibility that, during the device's functional life, the dielectric fluid can be introduced into the environment. To form a dielectric fluid with improved low temperature performance, a vegetable oil based fluid can be mixed with mineral oil based mineral oils or silicones, or formulated with significant amounts of non-biologically based synthetic additives. In many cases, however, these additives are expensive, toxic and/or non-biodegradable, and accidental spillage or leakage from the electrical appliance could damage the surrounding environment.

In one embodiment, this disclosure is directed to a dielectric fluid composition that includes at least one refined bleached vegetable oil that has been deodorized (RBD). The RBD vegetable oil has a sufficiently low pour point (less than about -20°C, preferably less than about 25°C, as measured according to each of ASTM D97 or ASTM D5950) to make the composition well suited for use in electrical appliances, especially in cold climates. Such RBD vegetable oils can be used in the compositions, dielectric fluid compositions and methods according to the other aspects of the present invention described herein.

In one aspect, the present disclosure is directed to a composition consisting of at least one vegetable oil and at least one antioxidant, wherein the composition has a pour point of less than about 20°C measured according to each of ASTM D97 or ASTM D5950.

In another aspect, the present disclosure is directed to a composition comprising at least one vegetable oil, at least one antioxidant, and at least one pour point depressant, wherein the composition has a pour point of less than about

-30°C measured according to each of ASTM D97 or ASTM D5950.

In yet another aspect, the present disclosure is directed to a dielectric fluid composition that includes at least one canola seed oil selected from Brassica Juneca, Brassica Campestris, and combinations thereof; and a synthetic ester.

The dielectric fluid compositions can be used in an electrical device such as e.g. transformers, switch mechanism, regulators and switches.

In yet another aspect, the present disclosure is directed to a method of making a dielectric fluid, including providing at least one refined, bleached canola seed oil that has been deodorized with a pour point of less than about -20°C as measured by at least one of ASTM D97 and ASTM D5950; treating the rapeseed oil with clay; to filter the rapeseed oil to produce a processed rapeseed oil.

The dielectric fluid compositions described herein have excellent electrical properties even when formulated with a minimal amount of non-biologically based compounds. In some embodiments, the dielectric fluid composition qualifies as at least one of: (1) readily biodegradable as defined by USEPA OPPTS 835.3110; (2) ultimately biodegradable as defined by USEPA OPPTS 835.3100; and (3) biodegradable as measured by method OECD 301. The excellent low temperature performance of the vegetable oil dielectric fluid compositions, as well as their environmentally safe and bio-based nature, allow the fluids to be used in appliances and in climatic areas where vegetable oil-based fluids have not previously has been applied. Since many components of the vegetable oil dielectric fluid compositions are derived from renewable, seed-based resources, the fluids can be easily produced and at a reasonable cost.

Details of one or more designs of the invention are presented in the attached drawings and the description below. Other features, purposes and advantages of the invention will be clear from the description and drawings and from the claims.

Brief description of drawings

Fig. 1 is a cross-sectional view of a transformer incorporating a vegetable oil dielectric fluid composition. Fig. 2 is a graph showing the viscosity of dielectric fluids over time at temperatures of -10°C and -20°C.

The present disclosure is directed to dielectric fluid compositions that include at least one refined, bleached vegetable oil that has been deodorized (RBD). The RBD vegetable oil has a pour point of less than approx. -20°C, preferably less than approx. -25°C, measured according to each of ASTM D97 or ASTM D5950. This low pour point makes the dielectric fluid compositions including the RBD vegetable oil well suited for use in electrical appliances, particularly in cold climates.

In one embodiment, this disclosure is directed to a dielectric fluid composition comprising at least one RBD vegetable oil and one antioxidant. The dielectric fluid composition has a pour point of less than approx. -20°C, preferably less than approx. -25°C.

The term RBD vegetable oil as used herein refers to crude vegetable oils that have been further processed at a vegetable oil refinery. Typically, to make an RBD vegetable oil, crude vegetable oil is degummed after adding water followed by alkali refining with a base such as NaOH, bleaching with clay and deodorized using vacuum steam stripping. Such RBD processing of oils is well known in the field. The processing steps remove contaminants from the crude vegetable oil that would cause poor dielectric performance. Crude vegetable oils also contain more wax components that would cause less desirable cold temperature performance.

The pour point of the dielectric fluid composition can be measured by each of two different methods, ASTM D97 or ASTM D5950 (pour point measurements per test method herein can vary by as much as + 3°C). ASTM D97, a manual technique, is an accepted standard test method for the determination of pour point in the electrical equipment industry. However, automated equipment to measure the pour point can in some cases provide improved speed and consistency of ASTM method D5950. However, the D5950 method is not approved in the electrical industry, although the lubricating fluid industry has converted to and approved a D5950 automated method.

The vegetable oil is preferably obtained by processing naturally occurring (not genetically modified, or non-GMO) seed stock, which can also be obtained from genetically modified (GMO) seeds, or from mixtures of oils obtained from GMO and non-GMO seeds.

A suitable vegetable oil for the dielectric fluid composition can be obtained by processing GMO rapeseed, non-GMO rapeseed and combinations thereof. Preferred oils are obtained from seeds grown in northern European regions. Oils obtained from non-GMO "winter" rapeseed grown in northern European climates have particularly low pour points, and are preferred for use in electrical appliances used in cold climates. Oils obtained from the seeds of the Brassica Juneca and Brassica Campestris plants are particularly preferred, and suitable oils are available from Cargill, Inc., Minneapolis, MN, under the trade name Agri-Pure 60 Rapeseed Oil.

While not wishing to be bound by any theory, currently available evidence indicates that RBD oils obtained from northern European rapeseed such as e.g. Brassica Juneca and Brassica Campestris seeds have a fatty acid distribution that results in a pour point of less than approx. -20°C, preferably less than approx. -20°C, measured according to each of ASTM D97 or ASTM D5950. Other RBD rapeseed oils such as e.g. those available from North American seed stores, exhibit a much higher pour point of approx. -10 to approx. -16°C. Compared to these North American oils, North European rapeseed oils derived from Brassica Juneca and Brassica Campestris can provide a significant advantage in low temperature applications.

Brassica Juneca and Brassica Campestris oils used in the dielectric fluid composition can be obtained from a single year's harvest, or oils from different growers can be blended to provide a vegetable oil dielectric fluid composition with the desired electrical, chemical and physical properties.

In addition to an exceptionally low pour point, dielectric fluid compositions including the preferred RBD Brassica Juneca and Brassica Campestris oils have excellent electrical properties after suitable processing.

The dielectric fluid compositions preferably have a dielectric strength of at least approx. 55 kv, preferably larger than approx. 60 kV. The dielectric strength can be measured by ASTM Method D1816 using a 0.08 inch (2 mm) gap between VDE electrodes. Determination of dielectric strength is well known in the field, and within the knowledge of the person skilled in the art.

The dielectric fluid composition also preferably has a flash point greater than 300°C, as well as a flash point greater than approx. 275°C. Both the fire point and the flash point can be measured by ASTM D92. Determination of the flash point is well known in the area and within the knowledge of the professional.

The dielectric fluid composition also preferably has a loss factor (DF) at 25°C of less than approx. 0.1%, and a loss factor at 100°C of less than approx. 4°. The loss factors can be measured using ASTM D924. Determining the loss factor is well known in the field and within the knowledge of the professional.

Other electrical, chemical and physical properties are presented in Table 4 below.

To ensure that the dielectric fluid composition remains flowable at relatively low temperatures, the vegetable oil used in the composition should preferably have a kinematic viscosity between 2 and 15 cSt at 100°C and less than 110 cSt at 40°C. Preferably, the fluids used in the dielectric fluid composition have a kinematic viscosity between approx. 20 and approx. 50 cSt at 40°C.

A common method for measuring the kinematic viscosity at 40/100°C is ASTM D445, however at temperatures of -10°C and -20°C and colder, another technique can be used. Yield stress and viscosity were measured using a Cannon mini-rotational viscometer (MRV) at ASTM D3829. The MRV functioned as a concentric cylinder viscometer in which the yield stress is determined by observing the movement of the cylinder under different types of applied stress. E.g. a 5 g weight can be used to apply yield stress, and the viscosity can be determined by measuring the time it takes to complete three revolutions. The time is multiplied by a constant, which depends on the cell used for the measurement, and the applied voltage, to determine the dynamic viscosity in centipoise (cP). The dynamic viscosity in cP is converted to kinematic viscosity in centistokes (cSt) by dividing the dynamic viscosity by the density of the fluid at the specific measurement temperature. Determination of viscosities is well known in the field and is within the knowledge of the person skilled in the art.

E.g. the density can be determined using a 250 ml volumetric flask with a 15 ml graduated cylinder as the neck. The internal volume was calibrated with water of known temperature and mass before measuring the fluid. The densities of the fluids at the temperature were calculated using the weight of the fluid with the measured volume.

The vegetable oil dielectric fluid composition further includes one or more antioxidant compounds. Useful antioxidant compounds include e.g. BHA (butylated hydroxyanisole), BHT (butylated hydroxytoluene), TBHQ (tertiary butylhydroquinone), THBP (tetrahydrobutrophenone), ascorbyl palmitate (rosemary oil), propyl gallate, and alpha, beta or delta tocopherol (vitamin E).

The antioxidant compounds may be present in the dielectric fluid composition with less than about 1% by weight, preferably less than approx. 0.5% by weight, based on the total weight of the composition.

In addition to the preferred rapeseed oils such as Brassica Juneca and Brassica Campestris, any of the dielectric fluid compositions described herein may optionally include other vegetable oils as extenders or to modify its properties, including adjusting the pour point. Any commercially available seed oil can be used, and suitable additional vegetable oils include e.g. soybean, sunflower, cabbage, corn, olive, cottonseed, saffron thistle, vernonia, lesquerella and combinations thereof. Of these additional oils, soybean oil and sunflower oil are preferred.

The additional vegetable oils may be present or used in any amount, so long as their presence does not substantially degrade the physico-chemical electrical properties of the composition.

In another design, the vegetable oil dielectric fluid composition consists of at least one vegetable oil as described above, at least one antioxidant as described above, and at least one agent for lowering the pour point. A wide variety of compounds can be used as pour point depressants, and preferred agents include polyvinyl acetate oligomers and polymers and/or acrylic oligomers and polymers. Suitable pour point depressants include (meth)acrylates such as those available from Rohmax, Philadelphia, PA, under the trade name Viscoplex. Alkyl methacrylates with a molecular weight of approx. 200,000, such as Viscoplex 10-310 has been found to be particularly suitable.

Agents for lowering the pour point can be used alone or possibly further diluted with a vegetable oil. Suitable vegetable oils for dilution of pour point depressants include e.g. vegetable oil diluted alkyl methacrylates available from Functional Products, Macedonia, OH, under the trade name PD-551.

Pour point depressants are present in the vegetable oil dielectric fluid composition up to approx. 4% by weight, preferably 0.2% by weight to approx. 2% by weight, and more preferably from approx. 0.4% by weight to 2% by weight.

Vegetable oil dielectric fluid compositions include an antioxidant and a pour point depressant typically having a pour point of less than about -30°C, preferably less than approx. -33°C, as measured by at least one of ASTM D97 and ASTM D5950. Including these additions, the composition of dielectric fluid with vegetable oil typically has a flash point greater than approx. 300°C, preferably greater than approx. 350°C, and a flash point greater than approx. 275°C, preferably greater than approx. 325°C. Other properties of a composition of dielectric fluid with vegetable oil with additives are shown in Table 5 below.

Any of the dielectric fluid compositions described herein may optionally include a small amount of one or more additives to inhibit the growth of microorganisms. Any antimicrobial substance compatible with the dielectric fluid can be mixed into the fluid. In some cases, compounds useful as antioxidants can also be used as antimicrobial agents. It is e.g. known that phenolic antioxidants such as BHA also exhibit some activity against bacteria, mould, viruses and protozoa, particularly when used with other microbial substances such as potassium sorbate, sorbic acid or monoglycerides. Vitamin E, ascorbyl palmitate and other known compounds are also suitable for use as antimicrobial additives.

Any of the compositions of dielectric fluid with vegetable oil described herein may further optionally include a colorant such as a dye or pigment. Any known color or pigment can be used for this purpose, and many are commercially available as food additives. The most useful dyes and pigments are those that are oil soluble. The dye is present in the composition in small amounts, typically less than approx. 1 ppm.

Under suitable circumstances, any of the vegetable oil dielectric fluid compositions described herein may optionally include a small amount of one or more mineral oil derived oils, such as e.g. mineral oils and/or polyalphaolefins. Mineral oils from naphthenic and paraffinic sources are typically refined and processed into transformer fluids that meet electrical industry standards ASTM D3687. Suitable mineral oil based dielectric fluids include e.g. those available from Petro-Canada under the trade name Luminol TR, those available from Calumet Lubricating Co. under the trade name Caltran 60-15, and those available from Ergon Refining Inc. under the trade name Hivolt II. Suitable polyalphaolefins have a viscosity from approx. 2 cSt to approx. 14 cSt at 100°C, and is available from Chevron under the trade name Synfluid PAO, Amoco under the trade name Durasyn and Ethyl Corp. under the trade name Ethylflo. Particularly preferred polyalphaolefins have a viscosity of approx. 4 cSt to approx. 8 cSt.

Mineral oil derived oils and polyalphaolefins can be incorporated into the composition with less than approx. 10% by weight, preferably less than approx. 5% by weight.

In another embodiment, the present description is directed to a composition of dielectric fluid with vegetable oil which includes at least one vegetable oil as described above, and a synthetic ester compound. In addition to the at least one vegetable oil and synthetic ester, the vegetable oil dielectric fluid composition preferably further includes an antioxidant as described above, and an agent for lowering the pour point as described herein.

The synthetic ester may be mixed with the vegetable oil and other optional components in an amount sufficient to modify the properties of the dielectric fluid composition, particularly to further lower the pour point for a particular cold temperature application. The term "synthetic ester" as used herein refers to esters prepared by a reaction between: (1) a bio-based or mineral oil-derived polyol; and (2) a linear or branched organic acid which may be biobased or mineral oil derived. The term polyol used herein refers to alcohols with two or more hydroxyl groups.

While the synthetic esters may be derived from biologically based compounds, mineral oil byproducts or combinations thereof, biologically based esters derived from renewable compounds produced by animals and plants are preferred.

As used herein, the term bio-based refers to compounds derived from substances produced by either animals and/or naturally occurring or cultivated plants. The plant and animal sources for the bio-based compounds may be GMO, non-GMO and combinations thereof, and non-GMO sources are preferred. The term "biobased" has the meanings set forth in USD A FB4P (2002 Farm Bill), e.g. 70 Fed. Reg. 1792 (January 11, 2005) and 71 Fed. Reg. 59862 (Oct. 11, 2006) (to be codified at 7 C.F.R. section 2902).

Suitable examples of bio-based synthetic esters include those prepared by reacting a polyol and an organic acid with carbon chain lengths of C8-C10 derived from a vegetable oil such as e.g. coconut oil. Suitable synthetic esters are available from Cargill (Brazil) under the trade name Innovatti, as well as from Hatco Chemical Co., Kearney, NJ. Among these synthetic esters are synthetic pentaerythritol esters with C7-C9 groups available under the trade name Envirotemp 200 (E200) from Cooper Power Systems and Hatco 5005 from Hatco Chemical Co., as well as trimethylolpropane (TMP) esters with C8-C10 groups available under trade name EXP 1906 from Innovatti and Hatco 2938 from Hatco Chemical Co., particularly well suited for use in the compositions of the electrical fluids. Other polyols suitable for reacting with organic acids to produce synthetic esters include e.g. neopentyl glycol, dipentaerythritol, and 2-ethylhexyl, n-octyl, isooctyl, isononyl, isodecyl and tridecyl alcohols.

The synthetic esters can be used in the composition of dielectric fluid with vegetable oil up to approx. 70% by weight, preferably approx. 30% by weight to approx. 70% by weight, and even more preferably approx. 25% by weight to 70% by weight. In general, larger amounts of the synthetic ester result in a dielectric fluid composition with a lower pour point. E.g. has some compositions of dielectric fluid with vegetable oil which include up to approx. 30% by weight synthetic esters a pour point of less than approx. -38°C, while some compositions that include up to approx. 70% by weight synthetic ester has a pour point of less than approx. -50°C, according to at least one of ASTM D97 and ASTM D5950.

While the incorporation of non-bio-based synthetic materials may improve certain properties of the vegetable oil dielectric fluid compositions described above, addition of these compounds also increases cost and may reduce the "environmentally friendly" nature of the composition. To ensure that spillage or leakage of the composition of dielectric fluid with vegetable oil will not have a significant influence on the environment, the composition should preferably be biodegradable, non-toxic and formulated with a minimum of non-based material. The composition of dielectric fluid with vegetable oil should preferably include at least 70% bio-based material and more preferably approx. 72.5% bio-based material.

E.g. biobased content can be determined using ASTM method D6866, which is based on the amount of biobased carbon in the material as a percentage of the mass of total organic carbon in the product.

The vegetable oil dielectric fluid compositions described above should also preferably be formulated to include a minimal amount of non-biodegradable material. The amount of synthetic and/or non-biodegradable additives in the vegetable oil dielectric fluid composition should preferably be limited so that the composition qualifies as at least one of: (1) readily biodegradable as defined by USEPA OPPTS 835.3110; (2) ultimately biodegradable as defined by USEPA OPPTS 835.3100; and (3) biodegradable as measured by the OECD 301 method.

Readily biodegradable as defined by USEPA OPPTS 835.3110 is a random classification of chemicals that have passed certain specified screening tests for ultimate biodegradability.

These tests are so rigorous that it is assumed that such compounds will rapidly and completely biodegrade in aqueous environments under aerobic conditions.

Ultimate biodegradability as defined by USEPA OPPTS 835.3100 is the breakdown of an organic compound to CO2, water, oxides or mineral salts of other elements, and/or to products associated with normal metabolic processes in microorganisms.

The compositions of dielectric fluid with vegetable oil described above should preferably be formulated so that they are essentially free of GMO material, which means that the composition does not include more than approx. 5% by weight GMO material. Even more advantageously, the composition should be substantially free of GMO material (no more than about 1% by weight GMO), and most preferably completely free of GMO material, meaning that no GMO material is present in the composition except as impurities. In the present application, it is mainly not completely excluded, e.g. that a composition which is essentially free of GMO material may be completely free of GMO material. When necessary, the word may be substantially removed from the definition of the invention.

The vegetable oil dielectric fluid compositions described above can be prepared by taking commercially available refined, bleached and deodorized (RBD) vegetable oils and treating the oils to remove impurities and improve electrical properties. The RBD oils are typically treated by removing moisture and stirring with an absorbent, such as an activated clay, to remove impurities that can be detrimental to the dielectric properties of the oils. In addition to or instead of the clay treatment step, RBD oils can be heated and/or filtered to remove particles, microorganisms and the like.

Preferably, the RBD oils are treated by adding approx. 10% by weight of heated clay (170°C) to the heated oil while stirring. The oil was then filtered to remove clay particles containing the absorbent contaminants followed by vacuum processing to less than approx. 10 torr.

Typically by following these or similar processing steps, preferred processed oils contain a maximum of approx. 200 ppm water, more preferably a maximum of approx. 100 ppm water.

After the steps to remove impurities, the processed oils can be used alone as dielectric fluids in electrical appliances. Before use, however, the oils are typically mixed with additives described above, e.g. antioxidants, agents for lowering the pour point, coloring agents and the like. The processed oils may be further blended with additional vegetable oils, synthetic esters, synthetic or mineral oil derived oils and the like to tailor their properties for a particular application.

In another embodiment, the present description is directed to electrical devices which have in them a composition of dielectric fluid including at least one RBD vegetable oil as described above and an antioxidant. The composition with dielectric fluid has a pour point of approx. -20°C, preferably less than approx. -25°C, as measured according to one of ASTM D97 or ASTM D5950.1 addition to the antioxidant, the composition of dielectric fluid in the electrical apparatus may further include any of the additives described above, including e.g. agents for lowering the pour point, additional vegetable oils, synthetic esters, mineral oils, polyalphaolefins and the like.

The vegetable oil dielectric fluid composition may be incorporated into any electrical equipment or apparatus including but not limited to transformers, switchgear, regulators and reclosers.

E.g. by referring to fig. 1, a transformer 10 includes a tank body 12 that encloses a transformer core coil assembly and windings 15. The core coil assembly and windings 15 are at least partially immersed in a dielectric fluid 18. The space between a surface of the fluid 18 and the tank body 12, referred to as the void 20, may optionally include an oxygen permeable container 24 housing an oxidation reducing composition 22 such as those described in US 2005/0040375. E.g. is a prepackaged oxygen-consuming compound, available commercially under the Ageless and Freshmax trade names, which can be packaged in a sack constructed of oxygen-permeable polymer film, a polyester felt, or cellulose paperboard. The tank body 12 can also include any features such as a threaded plug 28 with an inspection port 30, and a pressure release device 40.

The dielectric fluid compositions are preferably introduced into the electrical apparatus in a manner that minimizes exposure of the fluid to atmospheric oxygen, moisture and other contaminants that could adversely affect their performance. A preferred process includes drying the tank contents, evacuating and substituting air with dry nitrogen gas, filling under partial vacuum, and immediately sealing the tank. If the electrical device requires a void between the dielectric fluid and the tank cover, after filling and sealing the tank, the gas in the void can be evacuated and substituted with an inert gas, such as dry nitrogen.

Electrical transformers and switchgear are typically constructed by immersing the cores and windings and other electrical equipment in a dielectric fluid and enclosing the immersed components in a sealed housing or tank. The windings in larger equipment are also frequently wrapped with a cellulose or paper material. The compositions of dielectric fluid with vegetable oil described herein can also be used to protect and extend the useful life of cellulosic chains of paper insulating material. While not wishing to be bound by any theory, currently available evidence indicates that the vegetable oil dielectric fluids absorb water from the paper, which prevents the paper from hydrolytic degradation, and provides long-chain fatty acids that transesterify the cellulose and further reduce paper degradation, especially at higher operating temperatures for the equipment.

The compositions of dielectric fluids with vegetable oil can also be used to backfill existing electrical equipment incorporating other, less desirable electrical fluids. Backfilling of existing equipment can be carried out using any suitable method known in the art, although due to the increased sensitivity of vegetable oil fluids to moisture, the components of the electrical equipment may be dried prior to introduction of the vegetable oil based dielectric fluid. This can be particularly useful if the equipment includes cellulose or paper packaging, which can absorb moisture over time. Due to the relatively high solubility of water in vegetable oils, a vegetable oil fluid in itself can be used to dry out existing electrical equipment.

EXAMPLES

Example 1

Three different samples of RBD European rapeseed oil representing at least three different crop years were obtained and tested. The oils were obtained from a refinery in Antwerp, Belgium, which had rapeseed of the preferred types of the genera and species Brassica Juneca and Brassica Campestris.

The results are shown in Table 1 below.

Example 2

The pour points of the following fluids were measured according to ASTM D97 and ASTM D5950, and the results are shown in Table 2.

Example 3

The samples of European soybean oil and European rapeseed oil were obtained for analysis. The rapeseed oil was Cargill Agri-Pure 60 from Antwerp, Belgium and included the preferred types of the genera and species Brassica Juneca and Brassica Campestris. As received, RBD soybean oil had a pour point of approx. -10 to approx. -16°C according to ASTM D5950, while the RBD rapeseed oil had a pour point of -26°C.

The properties of the oils are shown in table 3 below.

The processed oils were then mixed with additives to enhance their performance as electrically insulating fluids. The processed oils are blended with 0.40 wt% BHT antioxidant, and 1.0 wt% of a pour point depressant, Viscoplex 10-310, available from Rohmax, Philadelphia, PA.

The properties of the resulting mixtures are shown in Table 5 below.

Example 4

The Euro rapeseed oil from Example 2 was blended with various synthetic esters as shown in Table 6 below.

In Table 6, soybean oil refers to a soybean-derived dielectric fluid available from Cooper Power Systems, Waukesha, WI, under the trade name Envirotemp FR3 fluid.

All compositions in Table 6 contain up to 1.0 wt% pour point depressant (Viscoplex 10-310, available from Rohmax), and up to 0.4 wt% antioxidant in vegetable oil.

Cl and C2 represent comparative examples.

E200 *= synthetic pentaerythritol ester with C7-C9 groups available from hatco Chemical Co. under the trade name Hatco 5005

EXP 1906 = synthetic ester with C8-C10 groups available from Hatco Chemical Co. under the trade name Hatco 2938.

Example C2 compared to Examples 3-2 and 3-4 shows the improved cold temperature performance of Euro rapeseed fluid compared to soybean oil based fluid.

Example 5

100% Euro rapeseed oil from Example 2 was blended with additives and tested to determine viscosity over extended periods of time at low temperature. Likewise, the test was also performed on soybean oil derived dielectric fluid available from Cooper Power Systems, Waukesha, Wl, under the trade name Envirotemp FR3 fluid. The results are shown in fig. 2.

The results in fig. 2 shows that, when introduced into electrical power equipment, the predominantly bio-based and biodegradable formulations according to the present described composition of dielectric fluid maintain a relatively constant viscosity for an extended period of time compared to a conventional vegetable oil.

Various designs of the invention have been described. These and other designs are within the scope of the following attached requirements.

Claims (16)

1. Electrical device, characterized in that it contains a dielectric fluid composition, wherein the dielectric fluid composition comprises at least one refined, bleached and deodorized rapeseed oil derived from non-GMO winter rapeseed grown in a northern European climate. 2. Electrical device according to claim 1, characterized in that the dielectric fluid composition has a further comprising at least one of a pour point depressant and an antioxidant. 3. Electrical device according to claim 2, characterized in that the antioxidant is selected from the group consisting of butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), tertiary butylhydroxyquinone (TBHQ), tetrahydroxybutrophenone (THBP), ascorbyl palmitate, propyl gallate, alpha-, beta- or delta-tocopherol and combinations thereof .. 4. Electrical device according to any of claims 1-3, characterized in that the dielectric fluid composition further comprises a synthetic ester. 5. Electrical device according to claim 4, characterized in that the synthetic ester is derived from biologically based compounds, petroleum by-products and combinations thereof. 6. Electrical device according to any of claims 4-5, characterized in that the synthetic ester is derived from biologically based compounds. 7. Electrical device according to any of claims 4-6, characterized in that the dielectric fluid composition comprises at least 30% by weight of the rapeseed oil 8. Electrical device according to any one of claims 1-7, characterized in that the dielectric fluid composition further comprises a second vegetable oil. 9. Electrical device according to claim 8, characterized in that the second vegetable oil is selected from the group consisting of soybean, cabbage of the genus Crambe, corn, olive, cottonseed, saffron, vernonia, lesquerella and combinations thereof. 10. Electrical device according to any of claims 8-9, characterized in that the vegetable oils have a viscosity of between 2 and 15 cSt at 100 °C, and less than 110 cSt at 40 °C. 11. Electrical device according to any one of claims 1-10, characterized in that the dielectric fluid composition further comprises a dye. 12. Electrical device according to any one of claims 1-11, characterized in that the electrical device is selected from a transformer, a switching system, a regulator and a re-connector. 13. Method for filling a transformer with a dielectric fluid, characterized in that it includes: - remove the original dielectric fluid composition, and - replacing the original dielectric fluid composition with a new dielectric fluid composition according to any one of claims 1-11 14. Method for reducing the rate of degradation of a paper insulating material in a transformer comprising a conductor insulated with the paper insulating material, characterized by using a dielectric fluid composition according to claim 1 in said transformer. 15. Fluid composition, characterized in that it consists of the dielectric fluid composition according to claim 1 and an antioxidant, where the fluid composition has a pour point of less than 25 °C. 16. Fluid composition, characterized in that it consists of the dielectric fluid composition according to claim 1, an antioxidant and a synthetic ester.