US3406111A - Transformer oil - Google Patents

Transformer oil Download PDF

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Publication number
US3406111A
US3406111A US209345A US20934562A US3406111A US 3406111 A US3406111 A US 3406111A US 209345 A US209345 A US 209345A US 20934562 A US20934562 A US 20934562A US 3406111 A US3406111 A US 3406111A
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oil
oils
sodium
transformer
oxidation
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US209345A
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Wynkoop Raymond
Jr Shirley C Bartlett
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Sunoco Inc
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Sun Oil Co
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    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
    • C10G29/00—Refining of hydrocarbon oils, in the absence of hydrogen, with other chemicals
    • C10G29/20—Organic compounds not containing metal atoms
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
    • C09K3/00—Materials not provided for elsewhere
    • C09K3/14—Anti-slip materials; Abrasives
    • C09K3/1454—Abrasive powders, suspensions and pastes for polishing
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B3/00—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties
    • H01B3/18—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances
    • H01B3/20—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances liquids, e.g. oils
    • H01B3/22—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances liquids, e.g. oils hydrocarbons

Definitions

  • This invention relates to novel transformer oil compositions and more particularly to uninhibited transformer oils which, under Doble Oxidation Test conditions, consistently exhibit power factors less than two percent throughout surprisingly long periods of oxidation and also low sludging tendency and high oxidation stability under the test conditions.
  • oils used as insulating media in transformers are well known in the art and a list of typical characteristics is given in the text by F. M. Clark entitled, Insulating Materials for Design and Engineering Practice (1962), page 135.
  • Such oils typically boil in the range of 460-775 F. and preferably have viscosities in the range of 55-60 S.U.S. at 100 F., as may be seen by reference to Wasson et al. Patent No. 3,000,807.
  • the other is a precipitation test in which one volume of the oil is diluted with five volumes of pentane, the mixture is allowed to stand at least eight hours and the presence or absence of a sludge precipitate is noted.
  • the endpoint of the Doble test is taken as the number of days of oxidation either before the acidity of the oil reaches 0.25 mg. of KOH per gram or before a positive precipitation test for sludge is obtained.
  • the best commercial transformer oils heretofore available generally have a life of only about three days under Doble test conditions. Longer life values could be obtained by adding an oxidation inhibitor to the oil but the use of such additive traditionally has been considered unacceptable by transformer manufacturers and users.
  • FIGURE 1 illustrates the type of curves found to be characteristic of commercially available transformer oils.
  • FIGURE 1 shows two curves that were obtained for commercial transformer oils A and B. It can be seen that for each oil a sharp hump in the power factor curve occurs in the earlier stages of oxidation. The power factor rapidly increases to a value considerably in excess of two percent, following which it decreases to a relatively low value and thereafter rises continuously.
  • the time of oxiice dation at which the peak of the hump is reached may differ with different oils, but it is characteristic for all uninhibited commercial transformer oils previously available that a hump in the PFVO curve is obtained and that the power factor at the peak of the hump is considerably above two percent.
  • the ideal transformer oil of course would be one that exhibits no increase whatever in power factor throughout the test life.
  • Transformer oils of the present invention are unlike any previously available in that the power factor curve obtained is relatively fiat.
  • FIG- URES 2-A and 2-B representing three uninhibited transformer oils (C, D and E) according to the present invention. These oils were prepared by the process described and claimed in the aforesaid copending applica tion Ser. No. 94,433, hereinafter described.
  • FIGURE 2-A shows the power factor curves for the three oils during the first 200 hours of oxidation by the Doble procedure, while FIGURE 2-B presents an extension of the curves for the oxidation period of 200-400 hours. It can be seen that the curves are remarkably fiat as compared to those obtained for other transformer oils.
  • the hump is insignificant and the power factor consistently remains less than two percent for at least 96 hours of oxidation (4 days).
  • Preferred compositions, such as the oils illustrated in FIGURES 2-A and 2-B, have power factors that remain consistently below two percent for oxidation times exceeding 192 hours (8 days) and often considerably in excess of such time.
  • They are napthenic petroleum distillates having a viscosity in the range of -65 S.U.S. at 100 F. and more preferably -60 S.U.S. at F.
  • the improved transformer oils of the invention can be prepared by the process described in the aforesaid application Ser. No. 94,433.
  • the preferred procedure involves first treating a naphthenic distillate of the abovespecified viscosity range with strong sulfuric acid, removing the acid sludge and then contacting the oil with adsorptive clay. Typically the oil is contacted with 10 lbs./bbl. of concentrated sulfuric acid and 20 lbs./bbl. of clay. At this stage the oil generally will have a Doble test life of only about 2 days and a nitrogen content of the order of 10 ppm. The oil is next treated at 250- 280 F.
  • alkali metal alkoxide in which the alkoxide portion corresponds to a secondary or tertiary alcohol of the C -C range.
  • the preferred alkoxide is sodium isopropoxide.
  • Other alkali metals, such as potassium or lithium, can be used and the alkoxide portion of the treating agent can correspond to other secondary or tertiary alcohols, such as t-butyl alcohol, but not to primary alcohols such as ethanol or n-propanol.
  • the alkoxide can be pre-formed by reacting sodium with an appropriate alcohol or it can be formed in situ in the oil by dispersing metallic sodium therein and then adding the alcohol.
  • the oil is contacted at 250-280 F. with carbon dioxide in molar excess of the amount of alkali metal used.
  • the oil can be contacted with carbon dioxide while being treated with the alkali metal alkoxide although this is not preferred.
  • the oil is then washed with water to remove the organo-metallic materials and thereafter is heated under vacuum while being sparged with an inert gas (e.g. nitrogen) to remove residual water. Finally the oil is contacted again at say 225 F.
  • the resulting refined product will have a nitrogen content less than 4 p.p.m. and generally not exceeding 2. p.p.m. and will exhibit the unique Doble test characteristics specified above. The product will give outstanding performance in transformer service.
  • the foregoing treatment removes little of the aromatic hydrocarbons present in the charge stock.
  • the presence of these naturally occurring aromatics in the refined product is highly important in providing the performance characteristics desired. It appears that the aromatics function as natural oxidation inhibitors and are essential for securing the unique Doble test characteristics as described above and illustrated in FIGURES 2-A and 2-B.
  • the extremely low nitrogen content obtained by the above-specitied treatment also is important in contributing to the outstanding stability of the present oils under the oxidizing conditions of the Doble test, as it has been found that if the nitrogen content exceeds 4 p.p.m. the oil generally will have a Doble test life of only about 2 days and a pronounced hump in the initial portion of the power factor curve will appear.
  • the aromatics in naphthenic oils having viscosities in the range of 50-65 S.U.S. at 100 F. appear to have molecular weights and structures such that they function more effectively as inhibitors under Doble test conditions than do the aromatics in oils of a substantially different viscosity range.
  • the fact is that the oil should have a viscosity of 50-65 S.U.S. at 100 F. to exhibit the outstanding Doble test characteristics illustrated in FIGURES 2-A and 2-B.
  • the charge oil was a naphthenic distillate stock of boiling range suitable for electrical transformer use.
  • the charge oil was first contacted at room temperature with 99% sulfuric acid in amount of 10 lbs./bbl. and was water washed and dried by air blowing. The oil was then heated to a temperature of about 270 F., and sodium in amount of 1% by weight was dispersed therein by means of a high speed stirrer. Then isopropanol was added in amount of 0.5% by volume on the oil, whereupon reaction occurred and the temperature rose about 10 F. over a'time of about 6 minutes and thereafter dropped. After about 30 minutes of mixing, carbon dioxide was bubbled into the mixture at a temperature of about 245 F. This caused the temperature to rise during a period of about 10 minutes, the amount of rise being somewhat greater than during the treatment with sodium and alcohol.
  • EXAMPLE II Another run was carried out as in the preceding example except that the amount of sodium used was increased to 2.5% by weight and the isopropanol to 1.0% by volume on the oil.
  • the finished oil in this case had a Doble life of 11 days,
  • EXAMPLE III Sodium recovered from the run of Example II was used for treating another batch of oil in the same manner except that in this case contact of the oil with sodium and with carbon dioxide was done concurrently. Again a Doble life of 11 days was obtained. This shows that the excess sodium can be reused and that successive and concurrent treaments with sodium and carbon dioxide each are efiective in preparing transformer oils according to the invention.
  • EXAMPLE IV Another run was carried out in the same manner as in Example II except that after the sodium treatment the oil was cooled to room temperature before being contacted with carbon dioxide. The resulting oil had a Doble life of 9 days. This shows that an elevated temperature is not required for the carbon dioxide treatment to be effective.
  • the low dissipation values obtained indicate that most of the sodium compounds can be removed from the reaction mixture by centrifuging and that a final water-washing or clay-treating step is not necessarily essential for producing a good transformer oil.
  • EXAMPLE VI The present example illustrates preparation of the present transformer oil composition in continuous manner.
  • the reactor used was provided with a high speed stirrer and with means for separately introducing streams of the charge oil, the alkoxide reagent which had been pre-formed and carbon dioxide and for continuously withdrawing the reaction mixture.
  • the alkoxide reagent was prepared by forming a concentrated dispersion of sodium in a small amount of the charge oil heated to a temperature above the melting point of sodium, cooling the dispersion to room temperature and then slowly adding isopropanol while stirring the mixture.
  • the charge oil was the same stock as described in Example I but had been treated with 10 lbs./bbl. of 99% sulfuric acid, neutralized by aqueous caustic soda and then dried by air blowing. It had a Doble test life of only 2 days.
  • the treatment was carried out by continuously passing the oil at a temperature of about 280 F. through the reactor at a rate providing a residence time of minutes, continuously feeding in a stream of the isopropoxide slurry in amount such that the sodium content of the reaction mixture was 0.56% by weight and continuously passing CO into the agitated mixture in molar excess of the isopropoxide.
  • Sodium-containing material was separated from the reactor efiiuent by sedimentation and the treated oil was finished by contact with 20 lbs./bbl. of adsorptive clay at 220 F.
  • the treated cil product was found to have a Doble test life of about 5 days, showing that it had good stability for transformer service.
  • EXAMPLE VII Another continuous run was made in the same manner as described above except that the sodium content of the reaction mixture was increased to about 1.1% by weight. The Doble test life of the oil was found to be about 7 days.
  • EXAMPLE VIII A sample of the acid-treated and neutralized charge oil used in Example VI was treated batchwise with tertiary butoxide as the treating agent.
  • the alkoxide was prepared by dispersing 0.5% by weight of sodium in the oil while hot, cooling to room temperature and slowly adding 1.1 moles of tertiary butanol per mole of sodium. The mixture was then heated to about 280 F. and agitated for 30 minutes. Carbon dioxide was then passed into the mixture at about 280 F. for 20 minutes. Sodium-containing material was removed from the mixture by settling.
  • the treated oil had a Doble Test life of 5 days.
  • EXAMPLE IX The charge oil was another batch of naphthenic distillate oil having the following properties: A.P.*I.
  • oils C, D and E are typical properties of oils C, D and E:
  • a transformer oil comprising a naphthenic petroleum distillate boiling in the range of 460-775 having a viscosity in the range of 50-65 S.U.S. at F., a viscosity-gravity constant in the range of 0.84-0.92 and a nitrogen content less than 4 p.p.-m. and, when tested under -D0ble Oxidation Test conditions in the absence of an added inhibitor, exhibiting the following characteristics: (1) a neutralization number less than 0.25 mg. KOH/g. at 96 hours oxidation time; (2) absence of sludge at 96 hours oxidation time; and (3) power factors during the oxidation period of 0-96 hours consistently less than 2 percent.
  • a transformer oil according to claim 1 having a nitrogen content not exceeding 2 ppm.
  • a transformed oil according to claim 1 having a power factor at 192 hours of oxidation less than 2 percent.
  • a transformer oil according to claim 1 having a viscosity in the range of 55-60 S.U.S. at 100 F.

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  • Chemical & Material Sciences (AREA)
  • Oil, Petroleum & Natural Gas (AREA)
  • Engineering & Computer Science (AREA)
  • Organic Chemistry (AREA)
  • Materials Engineering (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • General Chemical & Material Sciences (AREA)
  • Physics & Mathematics (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • Lubricants (AREA)
  • Production Of Liquid Hydrocarbon Mixture For Refining Petroleum (AREA)
US209345A 1960-03-18 1962-07-12 Transformer oil Expired - Lifetime US3406111A (en)

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US209345A US3406111A (en) 1960-03-18 1962-07-12 Transformer oil

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US1581060A 1960-03-18 1960-03-18
US9443361A 1961-03-09 1961-03-09
US209345A US3406111A (en) 1960-03-18 1962-07-12 Transformer oil

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US (1) US3406111A (enrdf_load_stackoverflow)
DE (1) DE1239048B (enrdf_load_stackoverflow)
GB (1) GB939699A (enrdf_load_stackoverflow)
LU (1) LU39905A1 (enrdf_load_stackoverflow)
NL (1) NL262451A (enrdf_load_stackoverflow)

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3619414A (en) * 1969-02-19 1971-11-09 Sun Oil Co Catalytic hydrofinishing of petroleum distillates in the lubricating oil boiling range
US3714021A (en) * 1969-10-22 1973-01-30 Kureha Chemical Ind Co Ltd Thermally stable insulating oil
US3753188A (en) * 1969-12-29 1973-08-14 Hitachi Ltd Inductive electric apparatus
US3839188A (en) * 1967-05-05 1974-10-01 Sun Oil Co Hydrorefined transformer oil and process of manufacture
US3839189A (en) * 1969-08-18 1974-10-01 Sun Oil Co Hydrorefined lube oil and process of manufacture
US3932267A (en) * 1974-09-11 1976-01-13 Shell Oil Company Process for producing uninhibited transformer oil
EP0497467A1 (en) * 1991-01-18 1992-08-05 Cooper Power Systems, Inc. Very low pour point dielectric

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5225159A (en) * 1991-12-13 1993-07-06 Henry Sawatzky Deodorization of sewage sludge-derived oils

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1856700A (en) * 1928-04-12 1932-05-03 Westinghouse Electric & Mfg Co Insulating oil
US3000807A (en) * 1958-12-04 1961-09-19 Exxon Research Engineering Co Blended transformer oil
US3095366A (en) * 1960-03-03 1963-06-25 Standard Oil Co Insulating oil

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1856700A (en) * 1928-04-12 1932-05-03 Westinghouse Electric & Mfg Co Insulating oil
US3000807A (en) * 1958-12-04 1961-09-19 Exxon Research Engineering Co Blended transformer oil
US3095366A (en) * 1960-03-03 1963-06-25 Standard Oil Co Insulating oil

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3839188A (en) * 1967-05-05 1974-10-01 Sun Oil Co Hydrorefined transformer oil and process of manufacture
US3619414A (en) * 1969-02-19 1971-11-09 Sun Oil Co Catalytic hydrofinishing of petroleum distillates in the lubricating oil boiling range
US3839189A (en) * 1969-08-18 1974-10-01 Sun Oil Co Hydrorefined lube oil and process of manufacture
US3714021A (en) * 1969-10-22 1973-01-30 Kureha Chemical Ind Co Ltd Thermally stable insulating oil
US3753188A (en) * 1969-12-29 1973-08-14 Hitachi Ltd Inductive electric apparatus
US3932267A (en) * 1974-09-11 1976-01-13 Shell Oil Company Process for producing uninhibited transformer oil
EP0497467A1 (en) * 1991-01-18 1992-08-05 Cooper Power Systems, Inc. Very low pour point dielectric

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LU39905A1 (enrdf_load_stackoverflow) 1961-06-20
NL262451A (enrdf_load_stackoverflow)
DE1239048B (de) 1967-04-20
GB939699A (en) 1963-10-16

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