US3062912A - Paper for use in the manufacture of electric cables and capacitors and other purposes - Google Patents
Paper for use in the manufacture of electric cables and capacitors and other purposes Download PDFInfo
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- US3062912A US3062912A US800618A US80061859A US3062912A US 3062912 A US3062912 A US 3062912A US 800618 A US800618 A US 800618A US 80061859 A US80061859 A US 80061859A US 3062912 A US3062912 A US 3062912A
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- paper
- impregnated
- glass fibre
- dielectric material
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- 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
- H01B3/185—Substances or derivates of cellulose
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
- H01B7/00—Insulated conductors or cables characterised by their form
- H01B7/02—Disposition of insulation
- H01B7/0241—Disposition of insulation comprising one or more helical wrapped layers of insulation
Definitions
- This invention is concerned with paper for use, after impregnation with an insulating oil or compound, as dielectric material. More especially it is concerned with paper for use in the manufacture of impregnated-paperinsulated electric cables.
- Paper is a felted fabric of vegetable fibres which for insulating purposes must usually have a high tensile strength to enable it to be lapped or wound at high speed without breakage and, for cable manufacture, must have good resistance to tearing and freedom from brittleness to permit the finished cable to be bent without damaging the paper of which the cable dielectric is built up. It should also have a high electrical breakdown strength, a low power factor and be of uniform thickness and density and capable of being uniformly impregnated with insulating oil or compound.
- capacitor tissue of a thicl ness of 1 mil or less which has been impregnated an electrical impulse breakdown strength of about 3000 kv./cm., when tested in single-sheet form, it has not hitherto been possible to manufacture cable insulating paper having an equivalent impulse breakdown strength but which has a thickness of 2 mils or more, the best 3 mil cable paper at present in use having a single sheet, impulse breakdown strength of little more than 2000 kv./cm.
- the proportion of glass fibre to yield a paper having optimum breakdown strength appears to be about 8%.
- the breakdown strength increases uniformly with the increase in glass fibre content, above 5% it increases less rapidly to a maximum of about 8% and then decreases at about the same rate until the content reaches about 10%. Further increase up to 20% in glass fibre content results in a substantially uniform decrease in breakdown strength but at a rate less steep than the rate of increase over the range 0% to 5% of glass fibre content.
- the size of the glass fibre appears to be critical. High breakdown strength is obtainable only with very fine glass fibre, that is to say, fibre having a diameter of one micron or less. It should also be short, for example, of an average length of about 0.1 mm. Fibre of this diameter is known in USA. as AAA grade. The incorporation in wood pulp of glass fibre obtained by treating ordinary glass wool having a fibre diameter of about 0.017 mm. in a beater fails to give a similar increase in the breakdown strength of the paper manufactured from it and results in a brittle sheet. To obtain the low power factor required of a cable dielectric, I prefer to use an alkali-free or low alkali content glass fibre, for example, glass fibre known in the USA. as type E.
- the degree to which the wood pulp is beaten is also of great importance. I have found that this should be ice extremely well-beaten in order to obtain an increase in the breakdown strength by the incorporation of very fine glass fibre.
- extremely well beaten I mean having a Schopper-Riegler (freeness) value closely approaching or equal to or even higher.
- the paper made in accordance with the invention can be used in the manufacture of impregnated paper insulated electric cables by conventional methods.
- the glass fibre used was of alkali free borosilicate glass (known as type E in U.S.A.) and of a diameter corresponding to that known as grade AAA in U.S.A.
- the pulp used was a first quality, unbleached, water-washed, sulphate wood pulp.
- the wood pulp was beaten until it had a Schopper-Riegler freeness value as indicated in the second column of the table below and the glass fibre, dispersed in low conductivity (demineralised) water, was then mixed with the wood pulp in the beater, 5% by weight (based on the glass fibre) of a water soluble methyl ether of cellulose, having a viscosity of 20 centipoises at 20 C.
- the single ply papers were made directly on the machine by the normal process. Although I would normally prefer to make the two ply papers on a twin wire machine, in this case they were made on a single wire machine by taking from the machine a wet web of paper on to a roll and later combining it with a web of paper passing through the machine at the first press.
- the substance (column 5) was obtained by weighing squares 5 x 5 crns. on an analytical balance. The thick ness was obtained by taking five readings on each square with a standard paper-makers dead-weight micrometer and the density was calculated from substance and thickness. The mechanical properties of the papers were found to be comparable with those of good quality cable paper.
- Samples of all five papers were vacuum dried and impregnated with a light mineral oil of the kind used in oil filled cables, the oil being a naphthenic-base oil with a high proportion of aromatics derived from low sulphur, low-wax crude oils of South American origin, subjected after distillation to acid and clay treatment and having a viscosity at 25 C. of 25 centistokes.
- the impulse strength of all of the impregnated papers was measured on single layers of the paper from each batch using A1" diameter electrodes, the sample being immersed in the impregnant. The impulse strength was calculated on the thickness of the impregnated paper.
- An impregnated paper insulated cable comprising at least one conductor, impregnated dielectric material surrounding said conductor, and an impervious sheath surrounding said dielectric material, in which the inner part of the impregnated dielectric material comprises paper made from an extremely well beaten wood pulp stock containing from 2% to not more than 20% by Table Per No. Sub- 'llnck- Density Imperme Impulse 7 Freecent of stance ness (clam ability Strcn gth Example ness Glass plies (glm (Mil) Gui-icy (kv./cm.)
- the accompanying drawing shows in cross-section an impregnated paper insulated power cable in which the inner part of the dielectric is of the paper referred to as Example 3 and the outer part is of a standard cable paper.
- An impregnated paper insulated cable comprising at least one conductor, impregnated dielectric material surrounding said conductor, and an impervious sheath surrounding said dielectric material, in which at least a part of the impregnated dielectric material comprises paper made from an extremely well beaten wood pulp stock containing from 2% to not more than 20% by weight of short glass fibre of a diameter not greater than one micron impregnated with an impregnant selected from the group consisting of mineral insulating oils and compounds based on such insulating oils.
- An impregnated paper insulated cable comprising at least one conductor, impregnated dielectric material surrounding said conductor, and an impervious sheath surrounding said dielectric material, in which at least a part of the impregnated dielectric material comprises paper made from an extremely well beaten unbleached, Water-washed, sulphate wood pulp stock containing from weight of short glass fibre of a diameter not greater than one micron impregnated with an impregnant selected from the group consisting of mineral insulating oils and compounds based on such insulating oils and the outer part of the impregnated dielectric material comprises paper not containing glass fibres impregnated with the same impregnant.
- An impregnated paper insulated cable comprising at least one conductor, impregnated dielectric material surrounding said conductor, and an impervious sheath surrounding said dielectric material, in which the inner part of the impregnated dielectric material comprises paper made from an extremely well beaten unbleached, water-washed, sulphate wood pulp stock containing from 2% to not more than 20% by weight of short, low alkali content borosilicate glass fibre of a diameter not greater than one micron, impregnated with an impregnant selected from the group consisting of mineral insulating oils and compounds based on such insulating oils and the outer part of the impregnated dielectric material comprises paper not containing glass fibres impregnated with the same impregnant.
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- Physics & Mathematics (AREA)
- Spectroscopy & Molecular Physics (AREA)
- Organic Insulating Materials (AREA)
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Description
Nov. 6, 1962 E. KELK 3,062,912 PAPER FOR USE IN THE MANUFACTURE OF ELECTRIC CABLES AND CAPACITORS AND OTHER PURPOSES Filed March 20, 1959 Inventor 0004/ A Home y United States Patent PAPER FOR USE 1N THE MANUFACTURE OF ELECTRKI CABLES AND CAPACETORS AND GTHER ?URPGST.S
Eric Kellr, Harmondsworth, England, assignor to British Insulated Cailenders (fables Limited, London, England, a British company Filed Mar. 20, 1950, Ser. No. 800513 Claims priority, application Great Britain Mar. 25, 1.958 8 Claims. Cl. 174-120) This invention is concerned with paper for use, after impregnation with an insulating oil or compound, as dielectric material. More especially it is concerned with paper for use in the manufacture of impregnated-paperinsulated electric cables.
Paper is a felted fabric of vegetable fibres which for insulating purposes must usually have a high tensile strength to enable it to be lapped or wound at high speed without breakage and, for cable manufacture, must have good resistance to tearing and freedom from brittleness to permit the finished cable to be bent without damaging the paper of which the cable dielectric is built up. It should also have a high electrical breakdown strength, a low power factor and be of uniform thickness and density and capable of being uniformly impregnated with insulating oil or compound. Although capacitor tissue of a thicl ness of 1 mil or less is available which has been impregnated an electrical impulse breakdown strength of about 3000 kv./cm., when tested in single-sheet form, it has not hitherto been possible to manufacture cable insulating paper having an equivalent impulse breakdown strength but which has a thickness of 2 mils or more, the best 3 mil cable paper at present in use having a single sheet, impulse breakdown strength of little more than 2000 kv./cm.
I have now found that a paper that meets all resonable requirements of the cable maker as regards mechanical strength, absence of brittleness, uniformity of thickness and density and impregnability, and low power factor yet has an unexpectedly high electrical breakdown strength which approximates to that of the best capacitor tissue can be obtained from an extremely well-beaten wood pulp stock, capable of yielding a very high impermeability paper, in which stock is incorporated from 2 to 20%, preferably from 5 to of very fine glass fibre.
The proportion of glass fibre to yield a paper having optimum breakdown strength appears to be about 8%.
Between 0 and 5% the breakdown strength increases uniformly with the increase in glass fibre content, above 5% it increases less rapidly to a maximum of about 8% and then decreases at about the same rate until the content reaches about 10%. Further increase up to 20% in glass fibre content results in a substantially uniform decrease in breakdown strength but at a rate less steep than the rate of increase over the range 0% to 5% of glass fibre content.
The size of the glass fibre appears to be critical. High breakdown strength is obtainable only with very fine glass fibre, that is to say, fibre having a diameter of one micron or less. It should also be short, for example, of an average length of about 0.1 mm. Fibre of this diameter is known in USA. as AAA grade. The incorporation in wood pulp of glass fibre obtained by treating ordinary glass wool having a fibre diameter of about 0.017 mm. in a beater fails to give a similar increase in the breakdown strength of the paper manufactured from it and results in a brittle sheet. To obtain the low power factor required of a cable dielectric, I prefer to use an alkali-free or low alkali content glass fibre, for example, glass fibre known in the USA. as type E.
The degree to which the wood pulp is beaten is also of great importance. I have found that this should be ice extremely well-beaten in order to obtain an increase in the breakdown strength by the incorporation of very fine glass fibre. By extremely well beaten I mean having a Schopper-Riegler (freeness) value closely approaching or equal to or even higher. The addition of such fibre to pulps having a substantially lower freeness value, eg a value of from 40 to 65 S.R. such as those normally used for the manufacture of cable paper, was found not to raise but to lower the breakdown strength of the paper. I prefer to use an unbleached, water-washed sulphate pulp, preferably of first quality.
The paper made in accordance with the invention can be used in the manufacture of impregnated paper insulated electric cables by conventional methods.
Examples of the manufacture of paper in accordance with the invention will hereinafter be described.
In all cases the glass fibre used was of alkali free borosilicate glass (known as type E in U.S.A.) and of a diameter corresponding to that known as grade AAA in U.S.A. The pulp used was a first quality, unbleached, water-washed, sulphate wood pulp. The wood pulp was beaten until it had a Schopper-Riegler freeness value as indicated in the second column of the table below and the glass fibre, dispersed in low conductivity (demineralised) water, was then mixed with the wood pulp in the beater, 5% by weight (based on the glass fibre) of a water soluble methyl ether of cellulose, having a viscosity of 20 centipoises at 20 C. in 2% aqueous solution, being added to the suspension of glass fibres as deflocculating agent. My preferred method of making a single and double ply papers in accordance with the invention from the pulp containing glass fibre thus obtained is as follows. After mixing the glass fibre with the pulp in the beater the mixture was diluted to .5% solids in the stock chest of the papermaking machine (again using low conductivity water) and diluted to 0.3% solids in the breast box of the machine prior to sheet formation on the Fourdrinier wire.
The single ply papers were made directly on the machine by the normal process. Although I would normally prefer to make the two ply papers on a twin wire machine, in this case they were made on a single wire machine by taking from the machine a wet web of paper on to a roll and later combining it with a web of paper passing through the machine at the first press.
Details of single ply and double ply paper made in this way are set out as Examples 1, 2 and 3 in columns ('3) 8) of the table below.
The substance (column 5) was obtained by weighing squares 5 x 5 crns. on an analytical balance. The thick ness was obtained by taking five readings on each square with a standard paper-makers dead-weight micrometer and the density was calculated from substance and thickness. The mechanical properties of the papers were found to be comparable with those of good quality cable paper.
For comparison purposes similar single and double ply papers were made in exactly the same way except that the glass fibre was omitted. Details of these papers are shown as Examples 4 and 5 respectively in the table below.
Samples of all five papers were vacuum dried and impregnated with a light mineral oil of the kind used in oil filled cables, the oil being a naphthenic-base oil with a high proportion of aromatics derived from low sulphur, low-wax crude oils of South American origin, subjected after distillation to acid and clay treatment and having a viscosity at 25 C. of 25 centistokes. The impulse strength of all of the impregnated papers was measured on single layers of the paper from each batch using A1" diameter electrodes, the sample being immersed in the impregnant. The impulse strength was calculated on the thickness of the impregnated paper. From column (9) of the table below it will be seen that the addition of by weight of the glass fibre to a single ply paper of thickness about 3 mils, made from the extremely well beaten pulp, gives an increase in impulse strength of 14% and that for similar paper in two ply form the addition of 5% of the glass fibre gives an increase of 31% and of 7 /2% of the glass fibre an increase of 62%.
To show the effect of varying the beating time and varying the glass fibre content, comparative tests were carried out on papers made on a laboratory sheet making apparatus from the same glass fibre and wood pulp as used in Examples 1-5. The same impregnant was used and the impulse strength Was measured under the same conditions. The results obtained are set out in the table below as Examples 6-15.
2% to not more than by weight of short, low alkali content borosilicate glass fibre of a diameter not greater than one micron, impregnated with an impregnant selected from the group consisting of mineral insulating oils and compounds based on such insulating oils.
5. A cable in accordance with claim 4 in which the content of the glass fibre in the stock is 510%.
6. An impregnated paper insulated cable in accordance with claim 4 in which the wood pulp stock is beaten to a Schopper-Riegler freeness value at least closely approaching 90.
7. An impregnated paper insulated cable comprising at least one conductor, impregnated dielectric material surrounding said conductor, and an impervious sheath surrounding said dielectric material, in which the inner part of the impregnated dielectric material comprises paper made from an extremely well beaten wood pulp stock containing from 2% to not more than 20% by Table Per No. Sub- 'llnck- Density Imperme Impulse 7 Freecent of stance ness (clam ability Strcn gth Example ness Glass plies (glm (Mil) Gui-icy (kv./cm.)
Sec/mil) 90 5 1 81 3.10 1.03 45, 000 1, 830 90 5 2 69 2. 50 1. O9 240, 000 2, 240 87 7% 2 90 3. 29 1. 08 9, 000 2, 770 90 O 1 70 2. 52 1. 10 150, 000 1, 600 90 0 2 75 2. 96 1.00 280, 000 1, 710 93 0 1 100 3. 5 1. 14 400, 000 1, S 93 5 1 84 2.9 1. 14 160, 000 3, 040 93 10 1 89 3. 0 1. 19 20, 000 3. 040 93 20 1 93 3.0 1. 21 ,000 3,020 93 1 83 3. 0 1. G9 500 2, 450 93 40 1 80 2. 9 1.08 80 1, 870 93 80 1 77 2. 8 1. 08 20 65 0 1 83 3. 1 1. 05 800 2, 100 65 5 1 84 3. 2 l. 04 400 1, 980 65 10 1 85 2. 2 1. O5 200 1, 940
It will be seen from Examples 6 to 15 that the highest impulse strengths were obtained when the freeness value was 93 and the glass fibre content from 520%.
The accompanying drawing shows in cross-section an impregnated paper insulated power cable in which the inner part of the dielectric is of the paper referred to as Example 3 and the outer part is of a standard cable paper.
What I claim as my invention is:
1. An impregnated paper insulated cable comprising at least one conductor, impregnated dielectric material surrounding said conductor, and an impervious sheath surrounding said dielectric material, in which at least a part of the impregnated dielectric material comprises paper made from an extremely well beaten wood pulp stock containing from 2% to not more than 20% by weight of short glass fibre of a diameter not greater than one micron impregnated with an impregnant selected from the group consisting of mineral insulating oils and compounds based on such insulating oils.
2. A cable in accordance with claim 1 in which the content of the glass fibre in the stock is 5-10%.
3. An impregnated paper insulated cable in accordance with claim 1 in which the wood pulp stock is beaten to a Schopper-Riegler freeness value at least closely approaching 90.
4. An impregnated paper insulated cable comprising at least one conductor, impregnated dielectric material surrounding said conductor, and an impervious sheath surrounding said dielectric material, in which at least a part of the impregnated dielectric material comprises paper made from an extremely well beaten unbleached, Water-washed, sulphate wood pulp stock containing from weight of short glass fibre of a diameter not greater than one micron impregnated with an impregnant selected from the group consisting of mineral insulating oils and compounds based on such insulating oils and the outer part of the impregnated dielectric material comprises paper not containing glass fibres impregnated with the same impregnant.
8. An impregnated paper insulated cable comprising at least one conductor, impregnated dielectric material surrounding said conductor, and an impervious sheath surrounding said dielectric material, in which the inner part of the impregnated dielectric material comprises paper made from an extremely well beaten unbleached, water-washed, sulphate wood pulp stock containing from 2% to not more than 20% by weight of short, low alkali content borosilicate glass fibre of a diameter not greater than one micron, impregnated with an impregnant selected from the group consisting of mineral insulating oils and compounds based on such insulating oils and the outer part of the impregnated dielectric material comprises paper not containing glass fibres impregnated with the same impregnant.
References Cited in the file of this patent UNITED STATES PATENTS 2,093,445 Hunter Sept. 21, 1937 2,315,736 Rosch Apr. 6, 1943 2,504,744 *Sproull et al Apr. 18, 1950 2,692,220 Labino Oct. 19, 1954 2,706,156 Arledter Apr. 12, 1955 2,734,095 Nears et al Feb. 7, 1956 2,772,157 Cilley et al Nov. 27, 1956
Claims (1)
1. AN IMPREGNATED PAPER INSULATED CABLE COMPRISING AT LEAST ONE CONDUCTOR, IMPREGNATED DIELECTRIC MATERIAL SURROUNDING SAID CONDUCTOR, AND AN IMPERVIOUS SHEATH SURROUNDING SAID DIELECTRIC MATERIAL, IN WHICH AT LEAST A PART OF THE IMPTEGNATED DIELECTRIC MATERIAL COMPRISES PAPER MADE FROM AN EXTREMELY WELL BEATEN WOOD PULP STOCK CONTAINING FROM 2% TO NOT MORE THAN 20% BY WEIGHT OF SHORT GLASS FIBRE OF A DIAMETER NOT GREATER THAN ONE MICRON IMPREGNATED WITH AN IMPTEGNANT SELECTED FROM THE GROUP CONSISTING OF MINERAL INSULATING OILS AND COMPOUNDS BASED ON SUCH INSULATING OILS.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB3062912X | 1958-03-25 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| US3062912A true US3062912A (en) | 1962-11-06 |
Family
ID=10920868
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| US800618A Expired - Lifetime US3062912A (en) | 1958-03-25 | 1959-03-20 | Paper for use in the manufacture of electric cables and capacitors and other purposes |
Country Status (1)
| Country | Link |
|---|---|
| US (1) | US3062912A (en) |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3225131A (en) * | 1963-01-18 | 1965-12-21 | Owens Corning Fiberglass Corp | Cable wrap |
| US3287259A (en) * | 1963-12-17 | 1966-11-22 | Exxon Research Engineering Co | Electrical insulating oil |
| EP0004833A3 (en) * | 1978-04-05 | 1979-10-31 | Gullfiber Ab | Paper-like fibre product and method of manufacturing such a product |
| US20030006654A1 (en) * | 2000-05-29 | 2003-01-09 | Jean-Pierre Chochoy | Rotary electric machine and method for making windings |
Citations (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2093445A (en) * | 1933-10-10 | 1937-09-21 | Callenders Cable & Const Co | Electric cable |
| US2315736A (en) * | 1940-04-24 | 1943-04-06 | Anaconda Wire & Cable Co | Electric cable |
| US2504744A (en) * | 1944-06-03 | 1950-04-18 | Gen Electric | Glass fiber sheet material |
| US2692220A (en) * | 1951-11-19 | 1954-10-19 | Glass Fibers Inc | Method for making glass paper |
| US2706156A (en) * | 1952-02-19 | 1955-04-12 | Hurlbut Paper Company | Method of making sheet material |
| US2734095A (en) * | 1956-02-07 | Plate separator for storage batteries | ||
| US2772157A (en) * | 1953-03-16 | 1956-11-27 | Raybestos Manhattan Inc | Production of mixed fibrous sheet material |
-
1959
- 1959-03-20 US US800618A patent/US3062912A/en not_active Expired - Lifetime
Patent Citations (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2734095A (en) * | 1956-02-07 | Plate separator for storage batteries | ||
| US2093445A (en) * | 1933-10-10 | 1937-09-21 | Callenders Cable & Const Co | Electric cable |
| US2315736A (en) * | 1940-04-24 | 1943-04-06 | Anaconda Wire & Cable Co | Electric cable |
| US2504744A (en) * | 1944-06-03 | 1950-04-18 | Gen Electric | Glass fiber sheet material |
| US2692220A (en) * | 1951-11-19 | 1954-10-19 | Glass Fibers Inc | Method for making glass paper |
| US2706156A (en) * | 1952-02-19 | 1955-04-12 | Hurlbut Paper Company | Method of making sheet material |
| US2772157A (en) * | 1953-03-16 | 1956-11-27 | Raybestos Manhattan Inc | Production of mixed fibrous sheet material |
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3225131A (en) * | 1963-01-18 | 1965-12-21 | Owens Corning Fiberglass Corp | Cable wrap |
| US3287259A (en) * | 1963-12-17 | 1966-11-22 | Exxon Research Engineering Co | Electrical insulating oil |
| EP0004833A3 (en) * | 1978-04-05 | 1979-10-31 | Gullfiber Ab | Paper-like fibre product and method of manufacturing such a product |
| US20030006654A1 (en) * | 2000-05-29 | 2003-01-09 | Jean-Pierre Chochoy | Rotary electric machine and method for making windings |
| US6774511B2 (en) * | 2000-05-29 | 2004-08-10 | Valeo Equipements Electriques Moteur | Rotary electric machine and method for making windings |
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