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USE OF CERTAIN AROMATIC COMPOUNDS AS ADDITIVES TO A DIELECTRIC LIQUID FOR
REDUCING THE VISCOSITY THEREOF
Field of the invention
The present invention generally relates to dielectric fluids for transformers,
and more
particularly to the use of certain aromatic compounds as additives to a
transformer liquid
in order to reduce the viscosity, and especially the low-temperature viscosity
thereof.
The invention also relates to the use of such dielectric liquid having reduced
viscosity in a
transformer.
Background
Magnetic and electrical fields create losses in a transformer. The energy of
these losses is
converted in the steel sheet core, the copper windings and other conductors
and parts to
so-called "loss heat" that leads to an increase of temperature in a
transformer. The heat
losses are different for different transformers. The high temperature in a
transformer
also stresses construction materials which are sensitive to high temperatures,
particularly
materials based on cellulose. According to IEC 60076 the design peak
temperature is 98 C
at the spots with highest temperature in the transformer in the case of a
transformer
with normal paper that is meant to last at least 40 years of service.
Transformer cooling
systems are engineered and designed to keep the temperature of the transformer
below
the design peek temperature under normal conditions. Normally transformer
cooling
systems are designed with a flowing dielectric liquid, commonly mineral oil.
The
effectiveness of the cooling depends on the transformer design, including i.a.
oil volume,
diameter of oil ducts and dimensions of the coolers and pumps. Beside design
factors,
the specific heat capacity, designated Cp, the viscosity of the oil at
operating
temperatures, and the flow properties (laminar/turbulent flow) also influence
the
cooling. Assuming that most mineral transformer oils have similar specific
heat capacity,
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it is the viscosity that plays the most important role in the heat transfer
and dissipation
calculations, and hence low viscosity oils have an advantage.
In cold climate areas there can be special requirements, such as e.g. cold
start-up
specifications, on viscosity and pour point of the dielectric liquid at low
temperatures.
The viscosity must be
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low enough to enable the liquid to start flowing; otherwise parts of the
transformer will heat up
to dangerous temperatures while cooler parts are clogged with cold and highly
viscous liquid.
Having a clogged or slow flowing system at start up may lead to overheating
and breakdown of
the transformer.
Not only must a dielectric liquid be a good heat dissipater but it must also
have good insulating
properties. The constant development and optimization of transformer
construction has led to
compact structures with the conductors as close to each other as the physics
allow without risk
of discharges going from one conductor to the other. Oil and paper have been
used as insulat-
ing material in oil filled electrical equipment for nearly a century. The main
technical reason for
this is that oil and paper are effective insulators, especially in
combination.
In a transformer the oil can, in some cases, be exposed to partial discharges
due to poor im-
pregnation of the solid insulation, or if the insulation is wet. Design or
assembly error may be
other factors causing partial discharges. With partial discharges, some oil
molecules will break
and the fragments may combine to form hydrogen and methane, which dissolve in
the oil.
Some reactions in the oil can absorb dissolved hydrogen, this is tested with
the industry stand-
ard gassing tendency IEC 60626 or ASTM D3300. In the gassing tendency standard
the oil is sat-
urated with hydrogen or nitrogen gas in a sealed container and exposed to
discharges. The hy-
drogen absorbing reactions occur mainly when aromatic structures are present,
and, to some
degree, are dependent on the amount of aromatic structures. Insulating oils
with high natural
aromatic content absorb more hydrogen gas in the gassing tendency tests but
this property can
also be altered by certain additives.
The trend for power transformers is that they are built for higher voltages
and run at higher
average loads closer to their maximum capacity. All parts of the transformer
need to be opti-
mized and so must also the dielectric liquid. The dielectric liquid must also
have excellent oxida-
tion stability to last in the transformer for many years at high temperature.
The dielectric liquid
must also have good solubility properties to keep any impurities formed in
solution where they
will make no harm.
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When choosing an insulating liquid for electrical equipment there are many
material
properties that need to be considered. The common requirements for mineral
insulting
oil are found in the specifications IEC60296 and ASTM D3487.
To fulfil all demands of modern high voltage transformers naphthenic super
grade oil is
most often chosen as the insulating liquid. The transformer design must take
the oil
properties into consideration and with high quality oil the design can be
optimised
better.
Today less refined oils are commonly used to obtain the desired low gassing
tendency
effect, since they contain more aromatic compounds. In other cases a well
refined oil is
used but with an additive. A commonly used additive is Tetralin'
(tetrahydronaphthalene), a volatile compound that also has some negative
health issues,
such as being suspected carcinogenic and being irritating to skin and eye.
The use of alkyl(C1-C4)naphthalene as an additive to mineral oil to impart to
the oil higher
gas-absorbing qualities is known from i.a. DE 24 53 863 and WO 93/21641.
US 2010/0059725 teaches that addition up to 10 wt% of reformer distillate,
containing 1-
and 2-ring aromatic compounds, to a transformer oil improves the gassing
tendency of
the transformer oil. Suitable 1- and 2-ring aromatics are e.g. alkylated
benzene,
naphthalene, alkylated naphthalenes, indanes, biphenyls and diphenyls.
US 3 932 267 teaches that addition of up to 5 % by weight of certain aromatic
compounds containing two or more six carbon membered fused or unfused rings at
least
one of which is a benzene ring, e.g. biphenyl, can improve the gassing
properties of an
uninhibited transformer oil, which oil has been produced according to a
specific process
disclosed therein.
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US 4 493 943 teaches the use of a combination of at least one diarylalkane,
and at least
one of mono- and and/or diolefin having two condensed or noncondensed aromatic
nuclei, for obtaining an electrical insulating oil having i.a. good hydrogen
absorbing
capacity. Preferred diarylalkanes are diarylmethane, 1,1-diarylethane, 1,2-
diarylethane,
and among these especially com-
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pounds having a benzene ring, which is not substituted with an alkyl group,
e.g. ar-
ylphenylethane. Other conventional electrical insulating oils such as
polybutene, mineral oils,
alkylbenzenes, alkylnaphthalenes and alkylbiphenyls can be added to the oil.
US 4 967 039 teaches that a silicone base oil for use as impregnant in an
electric power cable
for fire hazard conditions is rendered non-gassing by the addition of about 2-
8% of an aryl al-
kane having at least two benzene rings spaced apart by not less than one nor
more than two
aliphatic carbon atoms. According to US 4 967 039 the preferred additive is 1-
phenyl 1-(3,4 di-
methylphenyl) ethane, also known as PXE.
US 5 601 755 teaches a dielectric composition comprising benzyltoluene,
benzylxylene,
(methylbenzyl)toluene and (methylbenzyl)xylene. The composition can be mixed
with mineral
oils typically used in transformers.
Summary of invention
The present inventor has surprisingly found that diphenylmethane,
diphenylethane and similar
compounds when added in a small amount to mineral oil will markedly reduce the
viscosity of
the oil. The extent of reduction of viscosity is unexpected. For example, at -
40 C the viscosity of
the fluid is almost reduced by 50% when 5% diphenylmethane is added thereto.
Accordingly, in one aspect the present invention relates to the use of a C12-
C16 aromatic com-
pound consisting of a naphthalene, biphenyl, biphenyl ether, or diphenylalkane
structure, op-
tionally substituted with one, two, three, or four C1-C4 alkyl groups, as an
additive to a dielectric
liquid for a transformer in an amount of 1-10 % by weight, for reducing the
viscosity of the die-
lectric liquid.
Accordingly, by means of the present invention, the cold start-up
specification of a given dielec-
tric liquid will be improved, and the compound can thus be used as an additive
for improving
the cold start-up specification of a given dielectric liquid.
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The invention will thus enable a given dielectric liquid comprising the
inventive additive
to be used as having a cold start-up classification corresponding to a lower
temperature
as compared to the cold start-up specification of the oil without the
additive.
In one aspect the invention relates to the use of a dielectric liquid
containing the
inventive additive for improving the cold start-up performance and
characteristics of a
transformer.
In another aspect the invention consequently relates to the use of a
dielectric liquid
containing the inventive additive as having a cold start-up specification
corresponding to
a lower temperature than that of the cold start-up specification of the
dielectric liquid
without the additive.
In a further aspect the present invention relates to the use, e.g. including
start-up, of the
inventive transformer at an ambient temperature or temperature of the
transformer of
below -20 C.
In a further aspect, the present invention provides use of one or more C12-C16
aromatic
compounds selected from the group of compounds consisting of diphenylether,
diphenylnnethane, biphenyl, diphenylethane, nnethylbiphenyl, dimethylbiphenyl,
ethylbiphenyl, dimethylnaphthalene, trimethylnaphthalene,
ethylmethylnaphthalene,
propylnaphthalene, isopropylnaphthalene, methylpropylnaphthalene,
isopropylnnethylnaphthalene and diethylnaphthalene, as a viscosity-reducing
additive to
a dielectric liquid selected from the group consisting of naphthenic mineral
oil, paraffinic
mineral oil, synthetic ester, natural ester, synthetic isoparaffin, and
mixtures of any
thereof, for a transformer in a total amount of 1-10 % by weight.
In a further aspect, the present invention provides use of one or more C12-C16
aromatic
compounds selected from the group of compounds consisting of diphenylether,
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diphenylmethane, biphenyl, diphenylethane, methylbiphenyl, dimethylbiphenyl,
ethylbiphenyl, dimethylnaphthalene, trimethylnaphthalene,
ethylmethylnaphthalene,
propylnaphthalene, isopropylnaphthalene, methylpropylnaphthalene,
isopropylmethylnaphthalene and diethylnaphthalene, as a cold start-up
specification
improving additive to a dielectric liquid for a transformer selected from the
group
consisting of naphthenic mineral oil, paraffinic mineral oil, synthetic ester,
natural ester,
synthetic isoparaffin, and mixtures of any thereof, in an amount of 1-10 % by
weight for
improving the cold start-up specification of the dielectric liquid in terms of
the LCSET of
the liquid as established according to IEC 60296.
In a further aspect, the present invention provides use of a dielectric liquid
selected from
the group consisting of naphthenic mineral oil, paraffinic mineral oil,
synthetic ester,
natural ester, synthetic isoparaffin, and mixtures of any thereof, the
dielectric liquid
containing 1-10 % by weight of an additive comprising one or more C12-C16
aromatic
compounds selected from the group of compounds consisting of diphenylether,
diphenylmethane, biphenyl, diphenylethane, methylbiphenyl, dimethylbiphenyl,
ethylbiphenyl, dimethylnaphthalene, trimethylnaphthalene,
ethylmethylnaphthalene,
propylnaphthalene, isopropylnaphthalene, methylpropylnaphthalene,
isopropylmethylnaphthalene and diethylnaphthalene, in a transformer as a cold
start-up
performance improving dielectric liquid improving the cold start-up
performance of the
transformer.
In a further aspect, the present invention provides use of a dielectric liquid
selected from
the group consisting of naphthenic mineral oil, paraffinic mineral oil,
synthetic ester,
natural ester synthetic iso-paraffin, and mixtures of any thereof, containing
1-10 % by
weight of an additive comprising one or more C12-C16 aromatic compounds
selected from
the group of compounds consisting of diphenylether, diphenylmethane, biphenyl,
diphenylethane, methylbiphenyl, dimethylbiphenyl, ethylbiphenyl,
dimethylnaphthalene,
trimethylnaphthalene, ethylmethylnaphthalene, propylnaphthalene,
isopropylnaphthalene, methylpropylnaphthalene, isopropylmethylnaphthalene and
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diethylnaphthalene, in a transformer at a start-up or ambient temperature of
below -
20 C.
In a further aspect, the present invention provides a dielectric liquid
selected from the
group consisting of naphthenic mineral oil, paraffinic mineral oil, natural
ester, synthetic
ester, synthetic iso-paraffin, and mixtures of any thereof for a transformer
containing 1-
% by weight of an additive comprising one or more compounds selected from the
group of compounds consisting of diphenylether, diphenylethane,
methylbiphenyl,
dimethylbiphenyl, ethylbiphenyl, trimethylnaphthalene, ethylmethylnaphthalene,
10 propylnaphthalene, isopropylnaphthalene, isopropylmethylnaphthalene and
diethylnaphthalene.
By virtue of the invention the viscosity dependent heat transfer coefficient
of the system
will also be improved, and hence also the overall heat transfer coefficient of
the system.
By virtue of the reduced viscosity the invention allows for cooling of the
transformer to a
lower temperature. A lower temperature of the transformer will in turn extend
the
service life of the transformer. The improved heat transfer coefficient of the
system will
further enhance the cooling performance of the inventive dielectric liquid.
Also, the lower the temperature can be kept in a transformer, the lower the
power losses
will be. The lower power losses at lower temperatures are due to i.a. a lower
resistance
in the metal conductors, and a lower dielectric dissipation factor in the oil
at such lower
temperatures.
A number of the compounds of the invention are known from the prior art to
decrease
the gassing tendency of an insulating oil. The compounds of the invention can
thus be
used as a multipurpose additive to dielectric fluids to decrease both gassing
tendency
and viscosity thereof.
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In cold climate areas there is a need to have insulating oils with low
viscosity at low tempera-
tures in order to ensure safe start-ups. The additives of the present
invention enables achieve-
ment of a combination of a low viscosity at a vide temperature range, e.g.
from -40 C to
+100 C, and a negative gassing tendency, without affecting flash point
negatively or having
health and safety issues.
The present invention is especially intended for use in the power industry,
particularly in power
transformers. The cooling system of the inventive transformer can e.g. be of
ONAN, ONAF,
OFAN, OFAF, OFWF, ODAN, ODAF, or ODWF type.
The terms "oil", "dielectric oil", "dielectric liquid", and "dielectric fluid"
have been used inter-
changeably herein.
As used herein the term "cold start-up specification" of an oil is intended to
primarily refer to
the Lowest Cold Start Energizing Temperature (LCSET) as defined in IEC 60296
of the oil. In the
table below the maximum viscosity, and the maximum pour point for different
LCSETs are set
out.
LCSET Maximum viscosity Maximum pour point
C mm2/S
0 1 800 -10
-20 1 800 -30
-30 1 800 -40
-40 2 500 -50
Detailed description of the invention
In an attempt to support the modern transformers with top of the line
insulating oil a multipur-
pose additive has been tested for the application of both decreasing viscosity
and decreasing
gassing tendency. As a result C12-C16 aromatic compounds of a naphthalene,
biphenyl, biphenyl
ether, or diphenylalkane structure, optionally substituted with one, two,
three, or four C1-C4
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alkyl groups have been found to both decrease the viscosity and the gassing
tendency of a die-
lectric liquid. The extent of the reduction of the viscosity is however
unexpected.
For example, at 40 C addition of 5% by weight of the additive to a dielectric
fluid will typically
produce a decrease in viscosity about twice the expected decrease, e.g. as
estimated using Ref-
utas equation. The decrease in viscosity according to the invention will
generally be even great-
er at lower temperatures. For example, at -40 C, the addition of 5% of the
additive may even
result in a reduction of the viscosity of the dielectric fluid by about 50%.
Accordingly, the in-
ventive additive is generally more efficient at lower temperatures, such as at
0 C, and below.
A reduced viscosity of a given dielectric liquid will correspond to an
improved cold start-up
specification of the dielectric liquid. The inventive dielectric liquid
containing the additive can
thus be used in new applications, requiring a cold start-up specification
corresponding to a low-
er temperature than that of previous specifications of the dielectric liquid,
to which applica-
tions the dielectric liquid previously has not been qualified.
As mentioned previously the function of an oil in a transformer is cooling and
insulation. The oil
flows through the transformer and removes heat and therefore it is not only
viscosity but also
the viscosity dependent heat transfer coefficient that is interesting to look
at. Heat transfer
works in different ways depending on the design of the system to be cooled
(e.g. ONAN, ONAF,
OFAN, OFAF, OFWF, ODAN, ODAF, or ODWF). According to the present invention,
addition of
5% by weight of the additive to a dielectric fluid can e.g. improve the heat
transfer coefficient
of the system at 40 C with about 14%.
Examples of suitable compounds for use as an additive according to the
invention are diphe-
nylether, diphenylmethane, biphenyl, both isomers of diphenylethane, all
isomers of methylbi-
phenyl, dimethylbiphenyl, ethylbiphenyl, dimethylnapthalene,
trimethylnapthalene, ethylme-
thylnapthalene, propylnaphthalene, isopropylnapthalene,
methylpropylnapthalene, isopropyl-
methylnaphthalene and diethylnapthalene, or a mixture of any of the previous
compounds. An
especially preferred compound is diphenylmethane. Another preferred compound
is diphe-
nylether.
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The viscosity decreasing effect is been found to be greater when compounds in
the range of
C12-C14 are being used.
The C12-C16 compounds of a diphenylalkane structure are preferably diphenyl C1-
C3alkane com-
pounds, and more preferably diphenyl C1-C2alkane compounds, i.e.
diphenylmethane and di-
phenylethane structure compounds.
The inventive compounds preferably exhibit 0, 1, or 2 C1-C4 substituents, and
more preferably
.. no substituents. In preferred embodiments, any C1-C4substituents present
are C1-C3substitu-
ents.
The compounds used as additives according to the invention are preferably non-
halogenated.
The flash point is another important property of transformer oils, especially
when fire hazard is
a critical factor.
Compounds having a relatively high flash point are generally being preferred.
For example, di-
phenylmethane has a flash point around 130 C, as compared to 77 C for
tetralin.
According to the invention the additive is mixed into an insulating fluid for
the purpose of de-
creasing the viscosity, especially the low temperature viscosity, and to
decrease the gassing
tendency of the fluid. The insulating fluid could be e.g. of the following
kinds, naphthenic min-
eral oil, paraffinic mineral oil, natural ester, synthetic ester, poly-alpha
olefin, silicon oil, syn-
thetic iso-paraffin or a mixture of any of said insulating fluids.
A generally preferred group of dielectric fluids according to the invention is
the group compris-
ing naphthenic mineral oil, paraffinic mineral oil, natural ester, synthetic
ester, and mixtures
thereof.
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At low temperatures, e.g. at below 0 C, natural esters may be less suitable as
the dielectric liq-
uid, due the relatively low pour point.
Preferred insulating fluids for use at low temperatures are naphthenic mineral
oil, paraffinic
mineral oil, synthetic ester, and mixtures thereof.
The means of addition of the additive to the dielectric fluid and the mixing
thereof is not critical
as long as an adequate mixing of the components can be accomplished. For
example, if the ad-
ditive is solid when added to the dielectric fluid, the mixture should be
heated to a temperature
.. above the melting point of the additive, in order to enable adequate
mixing. A suitable temper-
ature of addition of the additive to the dielectric fluid is a temperature at
which both additive
and dielectric fluid are in a liquid state.
The additive should be added in an amount low enough in order that
crystallization of the addi-
.. tive in the dielectric fluid is avoided also at the low temperature end of
the intended service
temperature range. If crystallization of the additive occurs, the dielectric
solution may freeze,
or become unduly high in viscosity.
For example, depending on the specific oil, diphenylmethane may crystallize at
-40 C when
used in an amount greater than 5% in naphthenic insulating oil.
The solubility of the additive may also vary for different oils. For example,
a naphthenic oil will
probably be able to dissolve more additive than a paraffinic oil.
Examples of specific compounds for use in the invention are diphenylether,
diphenylmethane,
1,2-diphenylethane, 1,1-diphenylethane, and benzyltoluene.
In the table below values of certain properties for two compounds used in the
invention, viz.
diphenylmethane, and diphenylether, and for tetralin, respectively, are
provided for compari-
son.
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Tetralin Diphenylmethane Diphenylether
Ox. Stab. 500 h (1 % in naph- 500 h (2 % in naph- 500 h
(5 `)/0 in naph-
TEC61/25C thenic oil) - no im- thenic oil) - no im-
thenic oil) - no im-
pact on ox. stab. pact on ox. stab. pact on ox.
stab.
Flash point p.m. 77 C 130 C 115 C
ISO 2719
Boiling point 206-208 C 264-266 C 259 C
Of pure substance
Effect on Gassing ten- - 15 ml / min - 11 ml / min - 17 ml / min
dency when 1% added
_ASTM D2300
Hazard statements - H351: Suspected of - H400: Very toxic to - H319: Causes
seri-
causing cancer aquatic life. ous eye
irritation.
- H315: Causes skin - H410: Very
toxic to - H411: Toxic to
irritation, aquatic life with long aquatic
life with long
- H319: Causes serious lasting effects. lasting effects
eye irritation.
- H411: Toxic to
aquatic life with long
lasting effects
- H304: May be fatal if
swallowed and enter
airways
The above inventive compounds in the table have different hazard statements,
but the more
serious hazard statement of cancer suspicion that tetralin has is not stated
for any of them.
The present invention will now be described in more detail by means of the
following examples.
In the Examples the following dielectric fluids were used.
Oil Type Pour Point, PP (ISO 3016)
A Naphthenic Mineral Oil -63
B Naphthenic Mineral Oil -57
C Naphthenic Mineral Oil -66
D Paraffinic Mineral Oil -45
E Synthetic Ester -63
F Natural Ester -21
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Example 1¨ addition of 5 % by weight of diphenylmethane
% by weight of diphenylmethane, which has a melting point of about 25 C, was
added to 200
cm3 of naphthenic mineral oil (i.e. Oil A above) having a viscosity of 7.60
mm2/s at 40 C. The oil
5 was heated to 40 C, and mixed using a magnetic stirrer.
Using Refutas equation, and a value of the viscosity of diphenylmethane at 40
C of 2.14 mm2/s,
the resulting viscosity of the mixture at 40 C was estimated to be 7.02 mm2/s.
The actual viscosity of the resulting mixture was measured to be 6.53 mm2/s
using ASTM meth-
od D7042. In other words, the resulting decrease in viscosity was a factor of
about two larger
than expected.
Due to the high melting point of diphenylmethane it not possible to measure
the viscosity
thereof at lower temperatures. The reduction in viscosity of a mineral oil,
however, as com-
pared to the viscosity of the oil itself at a given low temperature, and that
of the resulting mix-
ture at same temperature, is extensive. The lower the temperature, the higher
the observed
relative viscosity reduction, until the solidification point of the mix
occurs. At -40 C the viscosity
can be reduced by almost 50% when 5% diphenylmethane is added to mineral oil
having a vis-
cosity within the viscosity range normally used for a transformer oil.
The heat transfer coefficient to the walls of a long pipe with the diameter of
5 cm and a fluid
flow speed of 1 m/s was estimated. The heat transfer coefficient for the pipe
was calculated
based on the the Nusselt-number, a friction factor f = 0.34, a dimensionless
number describing
turbulence in a system that in itself relies on viscosity, density, thermal
conductivity and heat
capacity. Adding 5% of diphenylmethane to Oil A will increase the heat
transfer coefficient at
40 C with about 14% in the previously described pipe-system.
The following values were used for the heat transfer coefficient calculation.
Density of the oil, d = 0.867 (kg/m3)
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Thermal conductivity of the oil, k = 0.13 (W/m=K)
Specific heat capacity of the oil, Cp = 1.875
Density of diphenylmethane, d = 0.872 (kg/m3)
Thermal conductivity of diphenylmethane, k = 0.135 (W/m=K)
Specific heat capacity of diphenylmethane, Cp = 1.59
Heat transfer coefficient, hwith = 184.5 with diphenylmethane
Heat transfer coefficient, hwithout = 161.9 without diphenylmethane
hwithihwithout = 1.14
Example 2- addition of diphenylmethane to different dielectric fluids
In this Example, using the mixing procedure in Example 1, diphenylmethane as
an additive was
mixed with different dielectric fluids to demonstrate the effect on the
viscosity of the fluids.
The gassing tendency of the resulting mixtures was established according to
ASTM D2300. Six
different dielectric fluids (A-F, as defined above) were used.
Gassing Visc -40 C Visc -30 C Visc -20 C Visc 0 C Visc 40 C Visc
Tendency ASTM ASTM ASTM D445 ASTM ASTM 100 C
ASTM D445 D445 (cSt) (cSt) D445 D7042 ASTM
D2300 (cSt) (cSt) (cSt)
D7042
(ml/min)
(cSt)
Oil A 33.5 2666 682.3 226.8 46.26
7.623 2.070
2.5%
5.9 1992 520.5 181.3 39.66
7.044 .. 1.985
additive
5.0%
-13.5 1463 411.3 149.4
34.63 6.535 1.910
additive
Oil B 7.0 5343
2.5%
-14.1 3818
additive
5.0%
-29.9 2756
additive
Oil C 31.8 2418
2.5%
4.7 1774
additive
5.0%
-15.8 1377
additive
Oil D _*** 268.5
2.5%
219.3
additive
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5.0%
- - 189.1 - - - -
additive
Oil E 1376 247.3 28.56
5.186
2.5%
1125 203.4 25.47
4.852
additive
5.0%
911.6 175.0 22.76
4.546
additive .
Oil F < PP < PP _*** 198.6 34.61
8.279
177.0 31.68 7.790
additive _ _
5.0%
157.5 29.02 7.347
additive
- Not measured
***Temperature very close to the pour point of the oil. Viscosity of the oil
at the relevant tem-
perature not measured.
The above results demonstrate that diphenylmethane significantly can reduce
viscosity, cold
temperature viscosity and gassing tendency. Other tests performed have shown
that diphenyl-
methane has no detectable impact on oxidation stability and very little impact
on the flash
point of the solution.
Example 3 - diphenylether
In this example, using the mixing procedure in Example 1, the effect of
diphenylether on the
viscosity at different temperatures, and gassing tendency, respectively, were
tested using Oils
A, D, E, and F, respectively.
Gassing Visc -40 C Visc -30 C Visc -20 C Visc 0 C Visc 40 C
Visc
Tendency ASTM ASTM ASTM ASTM ASTM 100 C
ASTM D445 D445 D445 (cSt) D445
D7042 ASTM
D2300 (cSt) (cSt) (cSt) (cSt)
D7042
(ml/min)
(cSt)
Oil A 33.5 2666 682.3 226.8 46.28 7.623
2.070
2.5%
-10.6 2134 555.2 190.1
7.123 1.999
additive
5.0%
-34.0 1717 460.4 162.6 36.51
6.704 1.936
additive
Oil D _>or* 268.5 118.2 34.73 7.375
2.188
5.0%
95.51 29.40 6.627
2.056
additive
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Oil E 1376 247.3 28.56
5.186
5.0%
974.2 187.0 23.28 4
6276
additive
Oil F < PP < PP 198.6 34.61
8.279
5.00/0
165.0 29.44 7.368
additive
- Not measured
***Temperature very close to the pour point of the oil. Viscosity of the oil
at the relevant tem-
perature not measured.
.. The above results demonstrate that diphenylether significantly can reduce
viscosity, cold tem-
perature viscosity and gassing tendency. Other tests performed have shown that
diphenylether
has no detectable impact on oxidation stability and very little impact on the
flash point of the
solution.
Example 4- biphenyl
In this example, using the mixing procedure in example 1, the effect of
biphenyl on viscosity
at different temperatures, and gassing tendency, respectively, were tested
using Oils A, D, E,
and F, respectively.
Gassing Visc -40 C Visc -30 C Visc -20 C Visc
Visc Visc
Tendency ASTM
ASTM ASTM D445 (cSt) 0 C 40 C 100 C
ASTM D445 (cSt) D445 (cSt) ASTM ASTM ASTM
D2300 D445 D7042 D7042
(ml/min) (cSt) (cSt) (cSt)
Oil A 33.5 2666 682.3 226.8 46.28 7.623
2.070
2.5%
-18.2 2078* 540.6 185.9 40.06 7.100 2.001
additive
5.0 /o
-58.7 2k* 36.41 6.648 1.923
additive
Oil D 268.5 118.2 34.73 7.375
2.188
2.5%
106.0 31.87
additive
5.0%
_** 29.07 6.552
2.045
additive
Oil E 1376 247.3 28.56
5.186
2.5%
1182 220.1
additive
5.0%
23.59
4.654
additive
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Oil F < PP < PP 198.6 34.61
8.279
5.0%
165.0 29.27 7.347
additive
- Not measured
* Value probably not stable, additive slowly precipitated.
** Additive precipitated.
*** Temperature very close to the pour point of the oil. Viscosity of the oil
at the relevant tern-
perature not measured.
The above results demonstrate that biphenyl significantly can reduce
viscosity, cold tempera-
ture viscosity and gassing tendency. Other tests performed have shown that
biphenyl has no
detectable impact on oxidation stability and very little impact on the flash
point of the solution.
Example 5- bibenzyl (also referred to as 1,2-diphenylethane or dibenzyl)
In this example, using the mixing procedure in example 1_, the effect of
bibenzyl on viscosity at
different temperatures, and gassing tendency, respectively, were tested using
Oils A, D, E, and
F, respectively.
Gassing Visc -40 C Vise -30 C Visc -20 C Visc 0 C Visc 40 C
Visc
Tendency ASTM ASTM ASTM ASTM ASTM 100 C
ASTM D445 D445 D445 (cSt) D445 (cSt) D7042
ASTM
D2300 (cSt) (cSt) (cSt)
D7042
(ml/min)
(cSt)
Oil A 33.5 2666 682.3 226.8 46.28 7.623
2.070
2.5%
20.0 2127 556.2 191.5 41.05 7.184 2.008
additive
8.5 1741 460.9 163.7 37.10 6.817 1.956
additive
Oil D 268.5 118.2 34.73 7.375
2.188
2.5%
106.2 31.97 6.954
2.121
additive
Oil E 1376 247.3 28.56
5.186
2.5%
25.61
4.904
additive
Oil F <PP <PP _*** 198.6 34.61
8.28
2.5%
178.8 31.45
7.736
additive
- Not measured
*** Temperature very close to the pour point of the oil. Viscosity of the oil
at the relevant tem-
perature not measured.
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The above results demonstrate that bibenzyl significantly can reduce
viscosity, cold tempera-
ture viscosity and gassing tendency. Other tests performed have shown that
bibenzyl has no
detectable impact on oxidation stability and very little impact on the flash
point of the solution.
