DESC:PRIORITY CLAIM
[0001] This application claims the benefit of Indian Provisional Application No. 201741017025 , filed in India on 15/05/2017 and titled “A DIELECTRIC FLUID COMPOSITION”
BACKGROUND
[0002] Embodiments of the present disclosure relate to a dielectric fluids, and more particularly, to a dielectric fluid composition.
[0003] Dielectric fluids reflect the condition of the transformers and shunt reactors in service. The role of dielectric fluid is crucial in the trouble free performance of power transformer, shunt reactors, switchgears, capacitors, etc. The dielectric fluid circulating in the main equipment does the task of insulating, cooling, diagnostic assessment etc. The dielectric fluids are used as electrical insulators in various applications. One such application includes high voltage power transmission systems, which employ equipment like transformers, capacitors, high voltage cables, and switchgear (namely high voltage switchgears). The dielectric fluid undergoes severe thermo-electric stress continuously and requires exceptional long term stability to withstand.
[0004] Dielectric fluids have another critical role in the insulation system and protects the solid insulation system degradation from moisture and oxygen.
[0005] Dielectric fluids are composition of blends of base oils and additives, additive can be phenolic or amine type. Dielectric fluids have to conform to international and national standards. To ensure dielectric fluids have all the necessary attributes for efficient performance stringent standards have been formulated by IEC, ASTM etc.
[0006] One such standard provided by IEC is oxidation stability of the dielectric fluid. The oxidation stability is a measure of a chemical reaction that occurs with a combination of the dielectric fluid and oxygen. The rate of oxidation increases with time and leads to an increase in the oil's viscosity and deposits of varnish and sludge in the equipment. The rate of oxidation is dependent on the quality and type of the base oil as well as the additive package used to manufacture the dielectric fluid.
[0007] The IEC standards for such oxidation stability are defined with respect to a testing period of 500 hours, where the dielectric fluid is accepted to meet the IEC standards if a maximum total acidity of the dielectric fluid is 0.30 mg KOH/g, a maximum sludge in the dielectric fluid is about 0.05% and a maximum dielectric dissipation factor of the dielectric fluid is about 0.05 at 90 degree Celsius. Although, some of the currently available compositions of the dielectric fluids adhere to the IEC standards, the composition of the dielectric fluids can be further improved to improve a service life of power transmission systems and reduce maintenance costs.
[0008] Hence, to overcome at least one of the above mentioned problems, there exists a need for an improved dielectric fluid having extended oxidation stability.
SUMMARY
[0009] This summary is provided to introduce a selection of concepts, in a simple manner, which are further described in the detailed description of the invention. This summary is neither intended to identify key or essential inventive concepts of the subject matter, nor to determine the scope of the invention.
[0010] In an embodiment of the present disclosure, a dielectric fluid composition having extended oxidation stability is disclosed. The composition comprising, a base oil 1 present by weight in a percentage range of about 5% to 90% of the total weight of the dielectric fluid, a base oil 2 present by weight in a percentage range of about 5% to 15% of the total weight of the dielectric fluid, a base oil 3 present by weight in a percentage range of about 5% to 30% of the total weight of the dielectric fluid; and one or more additives selected from an additive package present by weight in a percentage range of about 1% to 2% of the total weight of the dielectric fluid. Wherein, the dielectric fluid has kinematic viscosities at -40 °C in a range of about 900 to 1050 mm2/s, at -30 °C in a range of about 300 to 400 mm2/s, at 40 °C in a range of about 6 to 15 mm2/s and at 100 °C in a range of about 1 to 4 mm2/s.
[0011] In an another embodiment of the present disclosure, a dielectric fluid composition comprising one or more additives from the additive package in combination with the specific percentages of base oil 1, base 2 and base oil 3 is disclosed. The one or more additives selected from the additive package comprises at least one from the group of an oxidation inhibitor present in a percentage range of about 0.08% to 0.4% of the additive package, an anti-gassing agent present in a percentage range of about 0.01% to 0.4% of the additive package, a pour point depressant present in a percentage range of about 10 mg/kg to 40 mg/kg of the additive package, an anti-foaming agent present in a percentage range of about 2 mg/kg to 15 mg/kg of the additive package; and the mixtures there of the additive package.
[0012] To further clarify the advantages and features of the present invention, a more particular description of the invention will follow by reference to specific embodiments thereof, which are illustrated in the appended tables. It is to be appreciated that these tables depict only typical embodiments of the invention and are therefore not to be considered limiting in scope. The invention will be described and explained with additional specificity and detail with the appended tables.
DETAILED DESCRIPTION
[0013] For the purpose of promoting an understanding of the principles of the invention, reference will now be made to the embodiment illustrated in the tables and specific language will be used to describe them. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended. Such alterations and further modifications in the illustrated system, and such further applications of the principles of the invention as would normally occur to those skilled in the art are to be construed as being within the scope of the present invention.
[0014] It will be understood by those skilled in the art that the foregoing general description and the following detailed description are exemplary and explanatory of the invention and are not intended to be restrictive thereof.
[0015] The terms "comprises", "comprising", or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a process or method that comprises a list of steps does not include only those steps but may include other steps not expressly listed or inherent to such a process or method. Similarly, one or more devices or sub-systems or elements or structures or components preceded by "comprises... a" does not, without more constraints, preclude the existence of other devices, sub-systems, elements, structures, components, additional devices, additional sub-systems, additional elements, additional structures or additional components. Appearances of the phrase "in an embodiment", "in another embodiment" and similar language throughout this specification may, but not necessarily do, all refer to the same embodiment.
[0016] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this invention belongs. The system, methods, and examples provided herein are only illustrative and not intended to be limiting.
[0017] Embodiments of the present invention will be described below in detail with reference to the accompanying tables.
[0018] Embodiments of the present disclosure relate to a dielectric fluid composition having extended oxidation stability. The composition comprising, a base oil 1 present by weight in a percentage range of about 5% to 90% of the total weight of the dielectric fluid, a base oil 2 present by weight in a percentage range of about 5% to 15% of the total weight of the dielectric fluid, a base oil 3 present by weight in a percentage range of about 5% to 30% of the total weight of the dielectric fluid and one or more additives selected from an additive package present by weight in a percentage range of about 1% to 2% of the total weight of the dielectric fluid. Wherein, the dielectric fluid has excellent kinematic viscosities at -40 °C is from 900 to 1050 mm2/s, at -30 °C is from 300 to 400 mm2/s, at 40 °C is from 6 to 15 mm2/s and at 100 °C is from 1 to 4 mm2/s.
[0019] Further with respect to the above embodiment of the present disclosure, the dielectric fluid composition comprises the base oil 1, wherein the base oil 1 comprises a naphthenic carbon present by weight in a percentage range of about 20% to 40% of the base oil 1, a paraffinic carbon present by weight in a percentage range of about 50% to 70% of the base oil 1, and an aromatic carbon present by weight in a percentage range of about 0.1% to 4% of the base oil 1.
[0020] Further with respect to the present disclosure, the dielectric fluid composition comprises the base oil 2, wherein the base oil 2 comprises, an aromatic carbon present by weight in a percentage range of about 40% to 50% of the base oil 2, a naphthenic carbon present by weight in a percentage range of about 10% to 15% of the base oil 2 and a paraffinic carbon present by weight in a percentage range of about 35% to 40% of the base oil 2.
[0021] Further with respect to the present disclosure, the dielectric fluid composition comprises the base oil 3, wherein the base oil 3 comprises, an aromatic carbon present by weight in a percentage range of about 75% to 80% of the base oil 3, a naphthenic carbon present by weight in a percentage range of about 10% to 15% of the base oil 3 and a paraffinic carbon present by weight in a percentage range of about 5% to 10% of the base oil 3.
[0022] Further, the dielectric fluid composition also comprises the one or more additives selected from additive package, wherein the additive package comprises at least one from the group of an oxidation inhibitor, an anti-gassing agent, a pour point depressant, an anti-foaming agent and the combinations thereof.
[0023] Further, the dielectric fluid composition may comprise the one or more additives selected from the additive package. The one or more additive package comprises at least one from the group of an oxidation inhibitor present in a percentage range of about 0.08% to 0.4% of the additive package, an anti-gassing agent present in a percentage range of about 0.01% to 0.4% of the additive package, a pour point depressant present in a percentage range of about 10 mg/kg to 40 mg/kg of the additive package, an anti-foaming agent present in a percentage range of about 2 mg/kg to 15 mg/kg of the additive package and the mixtures there of the additive package.
[0024] Furthermore, the oxidation inhibitor may comprise a hindered phenol antioxidant or the like. The antigassing agent may comprise any one of C1 to C12 aromatic hydrocarbons or the like. Also, the total sludge percentage of the dielectric fluid composition is less than or equal to 0.05% and the acidity is less than or equal to 0.3 mg KOH/gm.
[0025] The test results for the dielectric fluid composition of the present disclosure as per the IEC60296:2012 standards have been disclosed below in table 1. The results disclosed in Table 1 showed that the composition is in full compliance with IEC 60296:2012 specification limits. The kinematic viscosity at -40 °C in a range of about 900 mm2/s to 1050 mm2/s, at -30 °C in a range of about 300 mm2/s to 400 mm2/s, at 40 °C in a range of about 6 mm2/s to 15 mm2/s and at 100 °C in a range of about 1 mm2/s to 4 mm2/s. The break down voltage is greater than or equal to 70 kV and the dielectric dissipation factor (DDF) at 90 oC is greater than or equal to 0.005. The anti-oxidants additives of the dielectric fluid composition is less than or equal to 0.40%. The oxidation stability of dielectric fluid composition for 500 hours of testing duration shows that the total acidity of the dielectric fluid is equal to or less than 0.3 mg KOH/g, the total sludge in the dielectric fluid is less than or equal to 0.05% and the dielectric dissipation factor of the dielectric fluid is less or equal to 0.05 at 90 degree Celsius.. The oxidation stability of dielectric fluid composition for 1000 hours of testing duration shows the total acidity of the dielectric fluid is 0.01mg KOH/g, the total sludge is 0.008% and the dielectric dissipation factor of the dielectric fluid is 0.0017 at 90 degree Celsius. As under IEC 60296:2012, there are no limits for 1000 hours oxidation stability, we are reporting the actuals.
TABLE 1
Characteristics IEC 60296: 2012 Specification Limits Dielectric Fluid Composition of the present disclosure
Kinematic Viscosity at 40o C mm2/s, Max 12.0 9.66
at -30o C mm2/s, Max 1800 350
at -40°C mm2/s, Max 2500 993
Pour Point oC, Max ? -40 -48
Water Content, mg/kg 20 10
Break Down Voltage, kV, Min 70 74
Density at 20 oC, g/ml, Max 0.895 0.827
DDF at 90 oC, Max 0.005 0.0005
Particle Count No General Requirement NAS 5 (16/14/11)
Appearance Transparent Clear & free from suspended impurities Transparent Clear & free from suspended impurities
Neutralization Value / Acidity, mg KOH/g, Max 0.01 Nil
Interfacial tension, mN/m, Min 40 48
Total Sulphur Content, % , Max 0.05 0.002
Corrosive Sulphur, silver strip, 100oC, 18 hrs Non Corrosive Non Corrosive
Cu Strip, 150 oC, 48 hrs Non Corrosive Non Corrosive
Cu Strip & Paper 150 oC, 72 hrs Non corrosive Non corrosive
DBDS, mg/kg, Max Not Detectable (< 5) Not Present
Antioxidant Additives, % Max 0.08 – 0.40 0.36
Metal Passivator, mg/kg Not detectable (< 5) Not Present
2-Furfural content, mg/kg, Max Not detectable (0.05) Nil
Stray Gassing No General Requirement Nil
Oxidation Stability, 500 Hrs
- Total acidity, mg KOH/g, Max 0.30 0.001
- Sludge, %, Max 0.05 0.004
- DDF at 900C, Max 0.05 0.0001
Oxidation Stability, 1000 Hrs -
- Total acidity, mg KOH/g, Max - 0.01

- Sludge, %, Max - 0.008
- DDF at 90°C, Max 0.0017
Gassing tendency, µL/mini No General Requirement +5
ECT No General Requirement Nil
Flash Point, PMCC, 0C , Min 135 160
Polycyclic Aromatics (PCA) content, % Max 3.00 0.5
Polychlorinated biphenyls (PCB) content Not Detectable (<2 mg/kg) Not Detected
Carbon Type Analysis, %
CA
CP
CN
-
-
-
9.36
60.83
29.81

[0026] The additional properties result of the dielectric fluid composition are given in the Table 2 below. The Rotating Vessel Oxidation property test results shows a time range of about 815 minutes that leads to the excellent oxidation resistance. The thermal conductivity property shows a results of around 0.140 W/mK and Specific Heat Capacity of the oil is around 1900 J/kgK. The dielectric fluid composition also leads to the faster cooling of the equipment. The negative impulse breakdown voltage shows a result that is greater than 300 kV that leads to safety during switching surges and lightening surges. The Biodegradability, OECD 301B, CO2 Evolution Test shows a result of greater than 60% that makes the fluid to be environmental friendly. The compatibility (miscibility) of the dielectric fluid composition with other dielectric fluids such as natural esters and synthetic esters may also be good.
TABLE 2
Other Properties of dielectric fluid composition of the present disclosure Results
Rotating Vessel Oxidation Test (RVOT), minutes 815
Thermal Conductivity, W/mK 0.140
Specific Heat Capacity, J/kgK 1900
Negative Impulse Breakdown Voltage, kV >300
Biodegradability, OECD 301B, CO2 Evolution Test Readily Biodegradable (>60% )
Compatibility (miscibility with other dielectric fluids) Fully miscible with Other mineral oils, Vegetable Oils & Synthetic Esters

[0027] Further, the test results for comparison of the dielectric fluid composition with the market-1 dielectric fluid is given below in the Table 3. The test was conducted for duration of about 0 Hours, 500 Hours and 1000 Hours respectively. The oxidation inhibitor content for the dielectric fluid composition of the present disclosure seems better when compared to the Market-1 dielectric fluid. For 1000 Hours of testing duration, the total acidity of the new dielectric fluid composition is measured at 0.01 mg KOH/g, total sludge percentage of the dielectric fluid is measured at 0.008% and the dielectric dissipation factor of the dielectric fluid is about 0.0017 at 90 degree Celsius substantiating its excellent long term stability as compared to market sample-1.
TABLE 3
Characteristics Dielectric fluid composition of the present disclosure Market-1 dielectric fluid
Durations in Hrs 0 500 1000 0 500 1000
Oxidation Inhibitor Content, % 0.36 0.29 0.09 0.33 0.23 0.00
Acidity, mg KOH/gm 0.0001 0.001 0.01 0.0001 0.01 2.69
Total sludge, % 0.0001 0.004 0.008 0.0001 0.0199 1.98
DDF at 90 degree Celsius 0.00004 0.0001 0.0017 0.00007 0.0139 0.29
Colour 0 0.5 1.0 0 0.5 3.5
[0028] Further, the test results for comparison of the dielectric fluid composition of the present disclosure with the Market-2 Dielectric Fluid is given below in the Table 4. The test was conducted for a duration of about 0 Hours, 500 Hours and 1000 Hours. The oxidation inhibitor content for the dielectric fluid composition is better when compared to the market-2 dielectric fluid. For 1000 Hours, the total acidity of the dielectric fluid composition is measure at 0.01 mg KOH/g, the total sludge in the dielectric fluid is measured at 0.008% and the dielectric dissipation factor of the dielectric fluid composition is measured at 0.0017 at 90 degree Celsius as compared to the Market-2 dielectric fluid which has the total acidity measured at 2.9 mg KOH/g, the total sludge is measured at 2.17% and the dielectric dissipation factor measured at 0.33 at 90 degree Celsius substantiating the excellent long term stability of the dielectric fluid composition of the present disclosure.
TABLE 4
Characteristics Dielectric fluid composition of the present disclosure Market-2 Dielectric Fluid
Durations in Hrs 0 500 1000 0 500 1000
Oxidation Inhibitor Content, % 0.36 0.29 0.09 0.4 0.23 0.00
Acidity, mg KOH/gm 0.0001 0.001 0.01 0.0001 0.02 2.9
Total sludge, % 0.0001 0.004 0.008 0.0001 0.02 2.17
DDF at 90 degree Celsius 0.00004 0.0001 0.0017 0.00005 0.016 0.33
Colour 0 0.5 1.0 0.5 1.5 4
[0029] Further, the test results for the comparison of the dielectric fluid composition with the Market-3 Dielectric Fluid is given below in Table 5. The test was conducted for a duration of about 0 Hours, 500 Hours and 1000 Hours. The oxidation inhibitor content for the dielectric fluid composition is better as compared to the Market-3 Dielectric Fluid. For 1000 Hours, The total acidity of the dielectric fluid composition is measured at 0.01 mg KOH/g, the total sludge of the dielectric fluid is measured at 0.008% and the dielectric dissipation factor of the dielectric fluid is measured at 0.0017 at 90 degree Celsius when compared to the total acidity of the Market-3 Dielectric Fluid measured at 1.9 mg KOH/g, the total sludge is measured at 1.87% and the dielectric dissipation factor is measured at 0.122 at 90 degree Celsius substantiating the excellent long term stability of the new dielectric fluid.
TABLE 5
Characteristics Dielectric fluid composition of the present disclosure Market-3 Dielectric Fluid
Durations in Hrs 0 500 1000 0 500 1000
Oxidation Inhibitor Content, % 0.36 0.29 0.09 0.4 0.23 0.00
Acidity, mg KOH/gm 0.0001 0.001 0.01 0.0001 0.022 1.9
Total sludge, % 0.0001 0.004 0.008 0.0001 0.02 1.87
DDF at 90 degree Celsius 0.00004 0.0001 0.0017 0.00005 0.016 0.122
Colour 0 0.5 1.0 0.5 1.5 6.5
[0030] Further, the test results for extended oxidation stability of the dielectric fluid composition are given in the Table 6. The oxidation stability tests for dielectric fluid composition are carried out for 0 hour, 500 hours, 1000 hours and 1669 hours respectively. The depletion rate of oxidation inhibitor content according to the test results is very slow i.e. 0.36% for 0 Hour, 0.29% for 500 Hours, 0.09% for 1000 Hours and 0.01% for 1669 hours. The total acidity of the dielectric fluid composition is equal to 0.0001 mg KOH/gm for 0 Hour, 0.001 mg KOH/gm for 500 Hours, 0.01 mg KOH/gm for 1000 Hours, 0.37 mg KOH/gm for 1669 Hours. Similarly the Total Sludge formation is low and the dielectric dissipation factor (DDF) at 90 degree Celsius is far better than limits under the standard. The exceptional stability of the new dielectric fluid enhances service life of the insulation system and the main equipment. Further, the results of accelerated test in rotating vessel oxidation test (RVOT) where the oil is tested at higher temperatures and with contamination in presence of oxygen at 90 psi pressure for the new formulation dielectric fluid given in Table 7, indicates that the new formulation has taken longer duration as compared to market samples.
TABLE 6
Characteristics Dielectric Fluid Composition of the present disclosure
Durations in Hrs 0 500 1000 1669
Oxidation Inhibitor Content, % 0.36 0.29 0.09 0.01
Acidity, mg KOH/gm 0.0001 0.001 0.01 0.37
Total sludge, % 0.0001 0.004 0.008 0.036
DDF at 90 °C 0.00004 0.0001 0.0017 0.043
Colour 0 0.5 1.0 2.5
Inter Facial Tension, (IFT) mN/m 49 39 32 15
Resistivity at 90 °C 333.9 169.4 161.2 3.79

TABLE 7
Property New Formulation Market-1 Dielectric Fluid Market-2 Dielectric Fluid Market-3 Dielectric Fluid
Rotating Vessel Oxidation (RVOT) Test as per ASTM D2112, Minutes 815 390 370 345

[0031] Furthermore, the dielectric fluid composition as disclosed in the present disclosure may be advantageous in providing an extended oxidation stability because of the reduction in acid formation and sludge accumulation. Also the dielectric dissipation factor (DDF) of the dielectric fluid composition are very low, that increases the service life of the liquid and the equipment in which they are used. The dielectric fluid composition has excellent flow-ability also at sub-zero temperatures with flash point (PMCC) more than or equal to 135°C because of good dielectric properties such as density, DDF, break down voltage and others with very low total sulphur content. The dielectric fluid composition consumes less amount of Inhibitor because of non-accumulation of oxidation products and absence of unsaturation and conductive contaminants.
[0032] It is to be understood that a skilled artisan will recognize the interchangeability of various features from different embodiments and that the various features described, as well as other known equivalents for each feature, may be mixed and matched by one of ordinary skill in this art to construct additional systems and techniques in accordance with principles of this disclosure. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention
,CLAIMS:WHAT IS CLAIMED IS:
1. A dielectric fluid composition having extended oxidation stability; the composition comprising:
a base oil 1 present by weight in a percentage range of about 5% to 90% of the total weight of the dielectric fluid;
a base oil 2 present by weight in a percentage range of about 5% to 15% of the total weight of the dielectric fluid;
a base oil 3 present by weight in a percentage range of about 5% to 30% of the total weight of the dielectric fluid; and
one or more additives selected from an additive package present by weight in a percentage range of about 1% to 2% of the total weight of the dielectric fluid;
wherein, the dielectric fluid has kinematic viscosities at -40 °C in a range of about 900 mm2/s to 1050 mm2/s, at -30 °C in a range of about 300 mm2/s to 400 mm2/s, at 40 °C in a range of about 6 mm2/s to 15 mm2/s and at 100 °C in a range of about 1 mm2/s to 4 mm2/s.

2. The dielectric fluid composition as claimed in claim 1, wherein the base oil 1 comprises:
a naphthenic carbon present by weight in a percentage range of about 20% to 40% of the base oil 1;and
a paraffinic carbon present by weight in a percentage range of about 50% to 70% of the base oil 1.
an aromatic carbon present by weight in a percentage range of about 0.1% to 4% of the base oil 1.

3. The dielectric fluid composition as claimed in claim 1, wherein the base oil 2 comprises:
an aromatic carbon present by weight in a percentage range of about 40% to 50% of the base oil 2;
a naphthenic carbon present by weight in a percentage range of about 10% to 15% of the base oil 2; and
a paraffinic carbon present by weight in a percentage range of about 35% to 40% of the base oil 2.

4. The dielectric fluid composition as claimed in claim 1, wherein the base oil 3 comprises:
an aromatic carbon present by weight in a percentage range of about 75% to 80% of the base oil 3;
a naphthenic carbon present by weight in a percentage range of about 10% to 15% of the base oil 3; and
a paraffinic carbon present by weight in a percentage range of about 5% to 10% of the base oil 3.

5. The dielectric fluid composition incorporating an additive from the additive package to improve the oxidation stability for extended service life during storage, processing and service as claimed in claim 1, wherein the one or more additives selected from the additive package comprises at least one from the group of an oxidation inhibitor, an anti-gassing agent, a pour point depressant, an anti-foaming agent and the combinations thereof.

6. The dielectric fluid composition as claimed in claim 1 wherein the one or more additives selected from the additive package comprises at least one from the group of:
an oxidation inhibitor present in a percentage range of about 0.08% to 0.9% of the additive package;
an anti gassing agent present in a percentage range of about 0.01% to 0.4% of the additive package;
a pour point depressant present in a percentage range of about 10 mg/kg to 40 mg/kg of the additive package;
an anti-foaming agent present in a percentage range of about 2 mg/kg to 15 mg/kg of the additive package; and the mixtures there of the additive package.

7. The dielectric fluid composition as claimed in claim 6, wherein an oxidation inhibitor more precisely present in a percentage range of about 0.08% to 0.4% of the additive package and the antigassing agent comprising from any one of C1 to C12 aromatic hydrocarbons.

8. The dielectric fluid composition as claimed in claim 5, wherein a total sludge percentage of the dielectric fluid is less than 0.05%.

9. The dielectric fluid composition as claimed in claim 5, wherein a acidity of the dielectric fluid is less than 0.3 mg KOH/gm.

10. The dielectric fluid composition as claimed in claim 5, wherein a dielectric dissipation factor of the dielectric fluid at 90°C is less than 0.05.