Note: Descriptions are shown in the official language in which they were submitted.
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VEGETABLE OIL DIELECTRIC FLUID COMPOSITION
This is a divisional application of Canadian Patent Application No.
2,683,310, filed May 13,2008. It should be understood that the expression "the
present invention" or the like used in this specification encompasses not only
the
subject matter of this divisional application but that of the parent
application also.
TECHNICAL FIELD
[0001] The present disclosure relates to dielectric fluids for use in
electrical
apparatus.
BACKGROUND
[0002] Dielectric (or insulating) fluid compositions used in electrical
distribution
and power equipment act as an electrical insulating medium, i.e., exhibit
dielectric
strength, and they transport generated heat away from the equipment, i.e., act
as a
cooling medium. When used in a transformer, for example, dielectric fluids
transport heat from the windings and core of the transformer or connected
circuits
to cooling surfaces.
100031 Liquid filled electrical apparatus 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 limited the range of applications for vegetable oil based
dielectric
fluid compositions, which typically have pour points above about -10 C.
SUMMARY
100041 Since some electrical apparatus use large amounts of dielectric fluid,
and
the dielectric fluid may remain in the apparatus for extended periods of time,
there
is a possibility that, during the service life of the apparatus, the
dielectric fluid may
be introduced into the environment. To create a dielectric fluid with improved
low
temperature performance, a vegetable oil base fluid may be blended with
petroleum based mineral oils or silicones, or formulated with significant
amounts
of non-biologically based synthetic additives. However, in many cases these
additives are expensive, toxic and/or non-biodegradable, and accidental
spillage or
leakage from the electrical apparatus could damage the surrounding
environment.
[0005] In one embodiment, this disclosure is directed to a dielectric fluid
composition including at least one refined, bleached and deodorized (RBD)
vegetable oil. The RBD vegetable oil has a sufficiently low pour point (less
than
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about -20 C, preferably less than about -25 C, as measured according to
either of
ASTM D97 or ASTM D5950) to make the composition well suited for use in
electrical apparatus, particularly in cold climates. Such RBD vegetable oils
may
be used in the compositions, dielectric fluid compositions and methods
according
to the other aspects of this invention recited herein.
[0006] 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 as measured according to either of
ASTM D97 or ASTM D5950.
100071 In another aspect, the present disclosure is directed to a composition
consisting of 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 as measured according to either of ASTM D97 or ASTM D5950.
[0008] In yet another aspect, the present disclosure is directed to a
dielectric fluid
composition including at least one rapeseed oil selected from Brassica Juneca,
Brassica Campestris and combinations thereof; and a synthetic ester.
[0009] The dielectric fluid compositions may be used in an electrical device
such
as, for example, transformers, switchgear, regulators and reclosers.
[0010] In yet anther aspect, the present disclosure is directed to a method of
making a dielectric fluid, including providing at least one refined, bleached
and
deodorized rapeseed oil 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;
and filtering the rapeseed oil to produce a processed rapeseed oil.
[0011] 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: (I) readily biodegradable as defined by USEPA
OPP'TS
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, allows use of the fluids
in
apparatus and in climatic areas in which vegetable oil based fluids have not
been
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previously employed. Since many components of the vegetable oil dielectric
fluid
compositions are derived from renewable, seed-based resources, the fluids may
be produced
easily and at a reasonable cost.
[0012] The details of one or more embodiments of the invention are set forth
in the
accompanying drawings and the description below. Other features, objects, and
advantages of
the invention will be apparent from the description and drawings, and from the
claims.
[0012a] In one embodiment, the parent application relates to an electrical
device having
therein a dielectric fluid composition, wherein the dielectric fluid
composition comprises at
least one refined, bleached and deodorized non-GMO Northern European winter
rapeseed oil
and at least one antioxidant, wherein the dielectric fluid composition has a
pour point of less
than -20 C as measured according to either of ASTM D97 or ASTM D5950, and
wherein the
electrical device is selected from the group consisting of a transformer, a
switchgear, a
regulator and a recloser.
10012131 In one embodiment, this divisional application relates to a
dielectric fluid
composition, comprising: 25% by weight to 70% by weight of at least one
Northern European
winter rapeseed oil; and a synthetic ester, wherein the synthetic ester is
produced by reacting a
polyol and an organic acid derived from a vegetable oil.
[0012c] In a further embodiment, this divisional application relates to a
dielectric fluid
composition, comprising: 25% by weight to 70% by weight of at least one non-
GMO
Northern European winter rapeseed oil; and a synthetic ester produced by
reacting a polyol
and an organic acid derived from a vegetable oil, wherein the synthetic ester
is selected from
the group consisting of pentaerithritol esters with C7-C9 groups and
trimethylpropane esters
with C8-C10 groups.
BRIEF DESCRIPTION OF DRAWINGS
[0013] FIG. 1 is a cross-sectional view of a transformer including a vegetable
oil dielectric
fluid composition.
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[0014] FIG. 2 is a plot showing the viscosity of dielectric fluids over time
at temperatures
of -10 C and -20 C.
DETAILED DESCRIPTION
[0015] This disclosure is directed to dielectric fluid compositions including
at least one
refined, bleached and deodorized (RBD) vegetable oil. The RBD vegetable oil
has a pour
point of less than about -20 C, preferably less than about -25 C, as measured
according to
either 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
apparatus,
particularly in cold climates.
[0016] In one embodiment, this disclosure is directed to a dielectric fluid
composition that
consists of at least one RBD vegetable oil and an antioxidant. The dielectric
fluid
composition has a pour point less than about -20 C, preferably less than about
-25 C.
[0017] 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 a RBD
vegetable oil,
crude vegetable oil is de-gummed after addition of water followed by alkali
refining with a
base such as NaOH, bleaching with clay and deodorization using vacuum steam
stripping.
Such RBD processing of oils is well known in the art. The processing steps
remove
contaminants from the crude vegetable oils that would cause poor dielectric
performance.
Crude vegetable oils
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also contain more waxy components that would cause less desirable cold
temperature performance.
[0018] The pour point of the dielectric fluid composition may be measured by
either of two different methods, ASTM D97 or ASTM D5950 (pour point
measurements per the test methods herein may vary as much as 3 C). ASTM
D97, a manual technique, is an accepted standard test method for determination
of
pour point in the electrical equipment industry. However, automated equipment
to
measure pour point may in some cases provide improved speed and consistency
per ASTM Method D5950. However, the D5950 method is not yet approved in the
electrical industry, although the lubricating fluids industry has converted to
and
approved the D5950 automated method.
[0019] The vegetable oil is preferably obtained by processing naturally
occurring
(non-genetically modified, or non-GMO) seed stocks, but may also be obtained
from genetically modified (GMO) seeds, or from blends of oils obtained from
GMO and non-GMO seeds.
[0020] One suitable vegetable oil for the dielectric fluid composition may 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" rapeseeds grown in northern
European climates have particularly low pour points, and are preferred for use
in
electrical apparatus operated in cold climates. Oils obtained from the seeds
of
Brassica Juneca and Brassica Campestris plants are particularly preferred, and
suitable oils are available from Cargill, Inc., Minneapolis, MN, under the
trade
designation Agri-Pure 60 Rapeseed Oil.
[0021] While not wishing to be bound by any theory, presently available
evidence
indicates that RBD oils obtained from northern European rapeseeds such as, for
example. Brassica Juneca and Brassica Campestris seeds, have a fatty acid
distribution that results in a pour point of less than about -20 C,
preferably less
than about -25 C, as measured according to either of ASTM D97 or ASTM
D5950. Other RBD rapeseed oils such as, for example, those available from
North
American seed stocks, exhibit a much higher pour point of about -10 to about -
16
C. Compared to these North American oils, northern European rapeseed oils
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derived from Brassica Juneca and Brassica Campestris can provide a significant
advantage in low temperature applications.
[0022] The Brassica Juneca and Brassica Campestris oils used in the dielectric
fluid composition may be obtained from a single year's harvest, or oils from
various cultivars may be blended to provide a vegetable oil dielectric fluid
composition with the desired electrical, chemical and physical properties.
[0023] 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 appropriate processing.
[0024] The dielectric fluid compositions preferably have a dielectric strength
of at
least about 55 kv, preferably greater than about 60 kV. The dielectric
strength may
be measured per ASTM method D1816 using a 0.08 inch (2 mm) gap between
VDE electrodes. The determination of dielectric strength is well known in the
art
and is within the knowledge of the skilled person.
[0025] The dielectric fluid composition also preferably has a fire point
greater than
300 C, as well as a flash point greater than about 275 C. Both fire point
and flash
point may be measured by ASTM D92. The determination of fire point is well
known in the art and is within the knowledge of the skilled person.
[0026] The dielectric fluid composition also preferably has a dissipation
factor
(DF) at 25 C of less than about 0.1%, and a dissipation factor at 100 C of
less
than about 4%. The dissipation factors may be measured using ASTM D924.
The determination of dissipation factor is well known in the art and is within
the
knowledge of the skilled person.
[0027] Other electrical, chemical and physical properties are set forth in
Table 4
below.
[0028] 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 about 20 and about 50 cSt at 40 C.
[0029] A common method for measuring the kinematic viscosity at 40/100 C is
ASTM D445, however, at cold temperatures of-10 C and -20 C and colder, a
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different technique may be used. The yield stress and viscosity were measured
using a Cannon mini-rotary viscometer (MRV) per ASTM D3829. The MRV
operated as a concentric cylinder viscometer in which the yield stress is
determined
by observing the movement of the cylinder under different applied stress. For
example, a 5 gram weight may be used to apply the yield stress and the
viscosity
may be determined by measuring the time to complete three revolutions. The
time
is multiplied by a constant, which depends on the cell used for the
measurement,
and the applied stress, 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
temperature of measurement. The determination of viscosities is well known in
the
art and is within the knowledge of the skilled person.
[0030] For example, the density may be determined using a 250 ml volumetric
flask with a 15 ml graduated cylinder for a neck. The internal volume was
calibrated with water at a known temperature and mass prior to measuring the
fluid. The densities of the fluids at temperature were calculated using the
weight
of the fluid with the measured volume.
[0031] The vegetable oil dielectric fluid composition further includes one or
more
antioxidant compounds. Useful antioxidant compounds include, for example, 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).
[0032] The antioxidant compounds may be present in the dielectric fluid
composition at less than about 1 wt%, preferably less than about 0.5 wt%,
based on
the total weight of the composition.
[0033] 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 may be
used, and suitable additional vegetable oils include, for example, soybean,
sunflower, crambe, corn, olive, cottonseed, safflower, vernonia, lesquerella
and
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combinations thereof. Of these additional oils, soybean oil and sunflower oil
are
preferred.
[0034] The additional vegetable oils may be present or used in any amount, as
long
as their presence does not substantially degrade the physical, chemical and
electrical properties of the composition.
100351 In another embodiment, 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 pour point depressant. A wide variety of
compounds may be used as pour point depressants, and preferred pour point
depressants include polyvinyl acetate oligomers and polymers and/or acrylic
oligomers and polymers. Suitable pour point depressant compounds include
(meth)acrylates such as those available from Rohmax, Philadelphia, PA, under
the
trade designation Viscoplex. Alkyl methacrylates with a molecular weight of
about 200,000, such as Viscoplex 10-310, have been found to be particularly
suitable.
[00361 The pour point depressant may be used alone or may optionally be
further
diluted with a vegetable oil. Suitable vegetable oil diluted pour point
depressant
compounds include, for example, the vegetable oil diluted alkyl methacrylates
available from Functional Products, Macedonia, OH, under the trade designation
PD-551. =
[00371 The pour point depressant is present in the vegetable oil dielectric
fluid
composition up to about 4 wt%, preferably about 0.2 wt% to about 2 wt%, and
more preferably from about 0.4 wt% to 2 wt%.
[00381 Vegetable oil dielectric fluid compositions include an antioxidant and
a
pour point depressant typically have a pour point of less than about -30 C,
preferably less than about -33 C, as measured by at least one of ASTM D97 and
ASTM D5950. Including these additives, the vegetable oil dielectric fluid
composition typically has a fire point greater than about 300 C, preferably
greater
than about 350 C, and a flash point of greater than about 275 C, preferably
greater than about 325 C. Other properties of a typical vegetable oil
dielectric
fluid composition with additives are shown in Table 5 below.
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[0039] 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 that is compatible with the dielectric fluid may be
blended into the
fluid. In some cases, compounds that are useful as antioxidants also may be
used as
antimicrobials. It is known, for example, that phenolic antioxidants such as
BHA also exhibit
some activity against bacteria, molds, viruses and protozoa, particularly when
used with other
antimicrobial substances such as potassium sorbate, sorbic acid or
monoglycerides. Vitamin
E, ascorbyl palmitate and other known compounds also are suitable for use as
antimicrobial
additives.
[0040] Any of the vegetable oil dielectric fluid compositions described herein
may further
optionally include a colorant such as a dye or pigment. Any known dye or
pigment can be
used for this purpose, and many are available commercially as food additives.
The most
useful dyes and pigments are those that are oil soluble. The colorant is
present in the
composition in minor amounts, typically less than about 1 ppm.
[0041] In appropriate circumstances, any of the vegetable oil dielectric fluid
compositions
described herein may optionally include a minor amount of one or more
petroleum derived
oils, such as, for example, mineral oils and/or polyalphaolefins. Mineral oils
from naphthenic
and paraffinic sources are typically refined and processed in to transformer
fluids that meet
the electrical industry standards per ASTM D3687. Suitable mineral oil-based
dielectric
fluids include, for example, those available from Petro-Canada under the trade-
mark Luminol
TR, those available from Calumet Lubricating Co. under the trade-mark Caltran
60-15, and
those available from Ergon Refining Inc. under the trade-mark Hivolt II.
Suitable
polyalphaolefins have a viscosity from about 2 cSt to about 14 cSt at 100 C,
and are available
from Chevron under the trade-mark Synfluid PAO, Amoco under the trade-mark
Durasyn and
Ethyl Corp. under the trade-mark Ethylflo. Particularly preferred
polyalphaolefins have a
viscosity from about 4 cSt to about 8 cSt, and originate from dimers, trimers
and tetramers of
chains of 10 carbons. The most preferred viscosity range for the
polyalphaolefins is from
about 6 cSt to about 8 cSt.
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[0042] The petroleum derived oils and polyalphaolefins may be incorporated
into
the composition at less than about 10 % by weight, preferably less than about
than
percent by weight.
[0043] In another embodiment, the present disclosure is directed to a
vegetable oil
dielectric fluid composition including 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 preferable
further
includes an antioxidant as described above and a pour point depressant as
described herein.
[0044] The synthetic ester may be blended 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 pour point for a
particular
cold temperature application. The term "synthetic ester" as used herein refers
to
esters produced by a reaction between: (1) a bio-based or petroleum-derived
polyol; and, (2) a linear or branched organic acid that may be bio-based or
petroleum-derived. The term polyol as used herein refers to alcohols with two
or
more hydroxyl groups.
[0045] While the synthetic esters may be derived from biologically based
compounds, petroleum by-products, or combinations thereof, biologically based
esters derived from renewable compounds produced by animals and plants are
preferred.
[0046] 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 "bio-based" has the meaning set forth in the USDA FB4P (2002 Farm Bill),
e.g. 70 Fed. Reg. 1792 (January 11, 2005) and 71 Fed. Reg. 59862 (October 11,
2006) (to be codified at 7 C.F.R. pt. 2902).
[0047] Suitable examples of bio-based synthetic esters include those produced
by
reacting a polyol and an organic acid with carbon chain lengths of C8-C10
derived
from a vegetable oil such as, for example, coconut oil. Suitable synthetic
esters are
available from Cargill (Brazil) under the trade designation lnnovatti, as well
as
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from Hatco Chemical Co., Kearney, NJ. Among these synthetic esters, synthetic
pentaerithritol esters with C7-C9 groups available under the trade designation
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 the trade designation EXP 1906 from Innovatti and Hatco 2938
from Hatco Chemical Co., are particularly well suited for use in the
dielectric fluid
compositions. Other polyols suitable for reacting with organic acids to make
synthetic esters include, for example, neopentyl glycol, dipentaerythritol,
and 2-
ethylhexyl, n-octyl, isooctyl, isononyl, isodecyl and tridecyl alcohols.
[0048] The synthetic esters may be used in the vegetable oil dielectric fluid
composition at up to about 70% by weight, preferably about 30% by weight to
about 70% by weight, and even more preferably about 25% by weight to 70% by
weight. Generally, larger amounts of the synthetic ester result in a
dielectric fluid
composition with a lower pour point. For example, some vegetable oil
dielectric
fluid compositions including up to about 30 wt% synthetic ester have a pour
point
of less than about -38 C, while some compositions including up to about 70
wt%
synthetic ester have a pour point of less than about -50 C, according to at
least one
of ASTM D97 and ASTM D5950.
[0049] While 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 costs and may reduce the
"environmentally friendly" nature of the composition. To ensure that a spill
or leak
of the vegetable oil dielectric fluid composition will not have significant
environmental impact, the composition should preferably be biodegradable,
nontoxic and formulated with a minimum of non-bio based material. The
vegetable oil dielectric fluid composition should preferably include at least
70%
bio-based material and more preferably at least about 72.5% bio-based
material.
[0050] For example, bio-based content can be determined by using ASTM Method
D 6866, which is based on the amount of bio-based carbon in the material as %
of
the mass of the total organic carbon in the product.
[0051] The vegetable oil dielectric fluid compositions described above should
also
preferably be formulated to include a minimum amount of non-biodegradable
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material. The amount of synthetic and/or non-biodegradable additives in the
vegetable oil dielectric fluid composition should preferably be limited such
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 method OECD 301.
[0052] Readily biodegradable as defined by USEPA OPPTS 835.3110 is an
arbitrary classification of chemicals which have passed certain specified
screening
tests for ultimate biodegradability. These tests are so stringent that it is
assumed
that such compounds will rapidly and completely biodegrade in aquatic
environments under aerobic conditions.
[0053] Ultimate biodegradability as defined by USEPA OPPTS 835.3100 is the
breakdown of an organic compound to CO2, water, the oxides or mineral salts of
other elements, and/or to products associated with normal metabolic processes
of
microorganisms.
[0054] The vegetable oil dielectric fluid compositions described above should
preferably be formulated to be essentially free of GMO material, which means
that
the composition includes no more than about 5% by weight GMO material. Even
more preferably, the composition should be substantially free of GMO material
(no
more than about 1 wt% GMO), and most preferably completely free of GMO
material, which means that no GMO material is present in the composition
except
for impurities. In the present application, substantially does not exclude
completely, e.g. a composition that is substantially free from GMO material
may
be completely free from GMO material. Where necessary, the word substantially
may be omitted from the definition of the invention.
[0055] The vegetable oil dielectric fluid compositions described above may be
made 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 absorber, such as an activated clay, to remove impurities, which can
be
detrimental to the electrical properties of the oils. In addition to or
instead of the
clay treatment step, the RBD oils may be heated and/or filtered to remove
particles,
microorganisms and the like.
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100561 Preferably, the RBD oils are treated by adding about 10 wt% heated clay
(170 C) to the heated oil while stirring. The oil is then filtered to remove
the clay
particles containing the absorbed contaminants followed by vacuum processing
to
less than about 10 torn
100571 Typically, following these or similar treatment steps, preferred
processed
oils contain a maximum of about 200 ppm water, more preferably a maximum of
about 100 ppm water.
[0058] Following the impurity removal steps, the processed oils may be used
alone
as dielectric fluids in electrical apparatus. However, prior to use the oils
are
typically blended with the additives described above, e.g. antioxidants, pour
point
depressants, colorants and the like. The processed oils may be further blended
with additional vegetable oils, synthetic esters, synthetic or petroleum
derived oils
and the like to tailor their properties for a particular application.
100591 In another embodiment, the present disclosure is directed at electrical
apparatus having therein a dielectric fluid composition including at least one
RBD
vegetable oil as described above and an antioxidant. The dielectric fluid
composition has a pour point of less than about -20 C, preferably less than
about -
25 C, as measured according to either of ASTM 097 or ASTM 05950. In
addition to the antioxidant, the dielectric fluid composition in the
electrical
apparatus may further include any of the additives described above, including,
for
example, pour point depressants, additional vegetable oils, synthetic esters,
mineral
oils, polyalphaolefins, and the like.
100601 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.
10061] For example, referring to Fig. 1, a transformer 10 includes a tank body
12
enclosing 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
headspace 20, may optionally include an oxygen permeable container 24 housing
an oxidation reducing composition 22 such as those described in US
2005/0040375. For example, a pre-packaged oxygen scavenging compound, such
12
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as is available commercially under the Ageless and Freshmax trade names, may
be
encased in a pouch constructed of a oxygen permeable polymer film, a polyester
felt or a cellulose pressboard. The tank body 12 may also include optional
features
such as a threaded plug 28 with a view port 30, and a pressure release device
40.
[00621 The dielectric fluid compositions preferably are introduced into the
electrical apparatus in a manner that minimizes the exposure of the fluid to
atmospheric oxygen, moisture, and other contaminants that could adversely
affect
their performance. A preferred process includes drying of the tank contents,
evacuation and substitution of air with dry nitrogen gas, filling under
partial
vacuum, and immediate sealing of the tank. If the electrical device requires a
headspace between the dielectric fluid and tank cover, after filling and
sealing of
the tank, the gas in the headspace may be evacuated and substituted with an
inert
gas, such as dry nitrogen.
[00631 Electrical transformers and switchgear typically are constructed by
immersing the core 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 frequently are also wrapped with a cellulose or
paper
material. The vegetable oil dielectric fluid compositions described herein
also may
be used to protect and extend the useful service life of the cellulose chains
of the
paper insulating material. While not wishing to be bound by any theory,
presently
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 breakdown, particularly at higher equipment operating temperatures.
[00641 The vegetable oil dielectric fluids compositions can also be used to
retrofill
existing electrical equipment that incorporate other, less desirable
dielectric fluids.
Retrofilling existing equipment can be accomplished using any suitable method
known in the art, though because of the increased sensitivity of vegetable oil
fluids
to moisture, the components of the electrical equipment may optionally be
dried
prior to the introduction of the vegetable oil based dielectric fluid. This
may be
particularly useful if the equipment includes cellulose or paper wrapping,
which
can absorb moisture over time. Because of the relatively high solubility of
water in
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vegetable oils, a vegetable oil fluid can itself be used to dry out existing
electrical
equipment.
EXAMPLES
Example 1
100651 Three different samples of RBD European Rapeseed oil that represent at
least three different crop years were obtained and tested. The oils were
obtained
from a refinery in Antwerp, Belgium, which processed rapeseeds from the
preferred genus and species types Brassica Juneca and Brassica Campestris.
10066] The results are shown in Table 1 below.
Table 1
Sample Crop Year Pour Point ( C)
(ASTM D97)
1 2004 -26
2 2005 -25
3 2006 -26
Example 2
100671 The pour points of the following fluids were measured according to ASTM
D 97 and ASTM D5950, and the results are shown in Table 2.
Table 2
Sample Pour Point ( C) Pour Point ( C)
ASTM D97 ASTM D5950
100% Euro-Rapeseed / "As received" -21 -20
100% Euro-Rapeseed / Clay treated- No additives -21 -24
Example 3
100681 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 genus and species types Brassica Juneca and
Brassica
Campestris. As received, the RBD soybean oil had a pour point of about -10 to
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about -16 C according to ASTM D5950, while the RBD rapeseed oil had a pour
point of -26 C.
[0069] The properties of the oils are shown in Table 3 below.
Table 3
Euro-Rapeseed Soybean Oil
Moisture 37 ppm 66 ppm *
Dielectric D1816 62 kV 46 kV *
DF.@ 25 C 0.04% 0.21%
DF @ 100 C 1.91% 5.67%
Acid No. 0.069 mg KOH/g 0.014 mg KOH/g
IFT 28.6 dynes/cm 27.1 dynes/cm
Flash Point 334 C 334 C
Fire Point 358 C 360 C
Pour Point -26 C -10 C
- *After 24 hours vacuum treatment, moisture = lppm,
D1816 = 54 kV
[0070] The RBD oils were then treated with clay and filtered, and the
properties of
the resulting processed oils are shown in Table 4 below.
Table 4
Euro-Rapeseed Soybean Oil
Moisture 3 ppm I ppm
Dielectric 01816 71 kV 61 kV
OF 25 C 0.02% 0.01%
DF @ 100 C 0.39% 0.38%
Acid No. 0.029 mg KOH/g 0.005 mg KOH/g
IFT 32.0 dynes/cm 30.0 dynes/cm
Flash Point 334 C 336 C
Fire Point 358 C 362 C
Pour Point -21 C -10 C
Viscosity @ 40 C 34.90 cSt 31.40 cSt
Viscosity @ 100 C 8.04 cSt 7.77 eSt
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[0071] The processed oils were then blended with additives to enhance their
performance as electrical insulating fluids. The processed oils were blended
with
0.40% by weight of BUT antioxidant, and 1.0 wt% of a pour point depressant,
Viscoplex 10-310, available from Rohmax, Philadelphia, PA.
[0072] . The properties of the resulting blends are shown in Table 5 below.
Table 5
Euro-Rapeseed Soybean Oil
Moisture 13 ppm 5 PPm
Dielectric DI816 73 kV 66 kV
DF @ 25 C 0.02% 0.03%
DF @ 100 C 1.53% 1.75%
Acid No. 0.047 mg KOH/g 0.028 mg KOH/g
1FT 32.2 dynes/cm 31.6 dynes/cm
Flash Point 332 C 330 C
Fire Point 358 C 360 C
Pour Point (D5950) -33 C -26 C
Pour Point (D97) -31 C -24 C
Viscosity @40 C 36.31 cSt 34.53 cSt
Viscosity @ 100 C 8.79 cSt 8.35 cSt
Volume Resistivity 74 x 1012 51 x 1012
Example 4
100731 The Euro Rapeseed Oil from Example 2 was blended with various synthetic
esters as shown in Table 6 below.
[0074] In Table 6, Soybean Oil refers to a soybean oil derived dielectric
fluid
available from Cooper Power Systems, Waukesha, WI, under the trade designation
Envirotemp FR3 Fluid.
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Table 6
Base Fluid Synthetic Synthetic Pour Pour Beneficial
Aspects
Ester Ester Point ( C) Point ( C) Fire Point
> >70% Bio-
E200 EXP 1906 (ASTM D (ASTM 300 C
based &
5950) D97)
Renewable
Example CI 0 70% -48 Yes (304 C)
Yes
30 '% Soybean Oil
Example C2 0 30% -33 -34 Yes (323 C)
Yes
70 % Soybean Oil
__________________________________________________________________
Example 3-1 0 70% -50 Yes (303 C)
Yes
30 % Euro-
Rapeseed
Example 3-2 0 30% -39 -38 Yes (321 C)
Yes
70 A) Euro-
Rapeseed
Example 3-3 '70% 0 -51 Yes No
30% Euro-
Rapeseed
Example 3-4 30% 0 -38 Yes No
70 % Euro-
Rapeseed
= Example 3-5 0 27.5% -39 -40
Yes (327 C) Yes
72.5 % Euro-
Rapeseed
= All blends in Table 6 contain up to 1.0% by wt pour point depressant
(Viscoplex 10-310,
available from Rohmax), and up to 0.4% by wt antioxidant in vegetable oil.
Cl and C2 represent comparative examples.
E200 = Synthetic pentaerithritol ester with C7-C9 groups available from Hatco
Chemical
Co. under the trade designation Hatco 5005
EXP 1906 = Synthetic ester with C8-C10 groups available from Hatco Chemical
Co. under
the trade designation Hatco 2938.
[0075] Example C2 compared to examples 3-2 and 3-4 show the improved cold
temperature performance of the Euro-Rapeseed fluid compared to a soybean oil
based fluid.
Example 5
[0076j The 100% Euro-Rapeseed oil from example 2 was blended with additives
and tested to determine the viscosity over extended periods of time at low
temperature. Likewise, the test was also performed on a soybean oil derived
dielectric fluid available from Cooper Power Systems, Waukesha, WI, under the
trade designation Envirotemp FR3 Fluid. The results are shown in Figure 2.
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[0077] The results of Fig. 2 show that, when introduced into electrical power
equipment,
the substantially bio-based and biodegradable formulations of the presently
described
dielectric fluid composition flow and maintain a relatively constant viscosity
for an extended
period of time compared to a conventional vegetable oil.
[0078] (Left blank intentionally)
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