DE2051562A1 - High voltage electrical cable - Google Patents

Description

PATENT Attorney Phone: (0271) 32409

DIPL-ING. ERICH SCHUBERT Telegram-Adr, PaI ₅ ChUb, Siegen

Postal check accounts: Cologne 106931, Essen 20362

Bank accounts: Paragraph: Patent attorney Dipl.-Ina. SCHUBERT, 59 Siegen, Eiserner Strasse 227 Deutsche Bank AG., P.O. Box 325 branches Siegen and Oberhausen (RhId.)

70 116 kitchen / dchm

Oct. 20, 1970

British Insulated Gallender's Cables Limited, - ■> * ■ " '21 Bloomsbury Street, London, WC1., England

For this application priority is _{claimed from British patent application Fr 0} 51783/69 of Oct. 22, 1969,

High voltage electrical cable

The invention relates to high voltage electrical cables with a layered or lamellar Dielektri kum, which has overlaps of insulating tape with an insulating liquid is impregnated, which is enclosed in a metal shell, which has sufficient flexibility has so that the cable can be wound on a drum. Such a lamellar dielectric is generally made up of overlapping turns of paper tape, although proposals have been made, a plastic film to be used alone or in layers with paper,

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and in British Patent 894,498 it was proposed to use a plastic film that was applied to either or both Sides has an adherent layer of fibrous material.

A specialist part of the use of plastic film in one impregnated lamellar dielectric, either alone or sandwiched between paper, is that it becomes more difficult to dry the layered dielectric and to impregnate, and another disadvantage of using plastic film alone is that ionization in the Joint spaces the plastic material, which forms the boundaries of the joint spaces, can degrade directly, which leads to a premature electrical breakdown

The advantages of using plastic and paper in combination are that compared to impregnated Paper the pulse resistance can be increased, the dielectric constant can be reduced, e.g. 3.4 to 2.6 to 2.8, the power factor can be reduced, e.g., from -0.002 to 0.001 or less, and in some cases the thermal conductivity the dielectric wall can be increased.

In British Patent 1,057,744 there is a method of overcoming the difficulty of drying and impregnating a lamellar dielectric composed of strips of polyolefin film and cellulose paper, described, wherein the plastic film is perforated before it is brought together in layers with paper to form a sandwich-like To form a structure which has a plastic film, paper adheres to both surfaces «

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The invention is based on the discovery that by appropriate Choice of impregnation agent and paper it is possible to manufacture a high-voltage cable of the type mentioned, of which a part of its dielectric or the entire dielectric is made up of impregnated strips of paper which is attached to a non-perforated plastic film adheres and improved electrical properties and / or smaller Dimensions than a similar cable in which the entire dielectric is made up of impregnated paper.

The cable according to the invention is an oil-filled cable, ie a cable which has a mobile impregnating agent of low viscosity, which is kept at a higher than atmospheric pressure, and the lamellar dielectric of the cable is at least partially composed of tapes which have a non-perforated plastic film, on the main surfaces of which a thin cellulose paper tape of low density and high impermeability is bound. The paper tapes and the plastic film are preferably bonded to each other that a pre-stressed laminate material is formed, that is, a layer of material as it is formed by an extruded melted plastic strips as soon as it leaves an extruder, between two strips of paper having a g portion of of the layer material form, is captured or introduced.

By the term "low viscosity", as applied when impregnating agent is a viscosity of less than 57 centistokes at 20 ⁰ C and 11 centistokes at 60 ⁰ G, and preferably less than 25 centistokes at 20 ⁰ G to understand.

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The term "low density" as used in relation to that

Paper is called, means a density of less than 0.8

and preferably less than 0.75 g / cm.

The term "high impermeability" as used in relation to paper means impermeability, which is comparable to or higher than that normally used with oil-filled cables, and preferably in the higher part of the range, e.g. 10,000 Gurley seconds or higher. '

By "cellulosic paper" is meant a paper which consists essentially entirely of cellulosic fibers.

The preferred paper is uncalendered paper electrical grade of inter-fiber length and a density of 0.7 g / cm and a Gurley impermeability of more than 10,000 seconds. One such paper is a Kraft spool wrapping paper, which is generally based on the British standard BS 690: 1956 » Class 1A, manufactured to the very high level of chemical purity that normally makes capacitor foils heard.

The paper layers can be coated with an active material of the type described in British. Patent specification 1 185 474 is described, loaded or »charged, i.e. with aluminum oxide or another active metal oxide, hydrogenated Metal oxide, hydroxide, 'carbonate or a basic carbonate, which sorptive abilities compared to those of aluminum oxide has to the deterioration in electrical properties as a result of contamination of the impregnation agent by residues Keep your plastic to a minimum.

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The plastic film is preferably made of polyethylene or polypropylene, aber'alternativ also polycarbonates, polysulfones, saturated linear polyesters (eg polyethylene terephthalate _0), polyphenylene oxide, poly-4-niethylpenten-i, PoIytetrafluoräthylen, Ä'thylenpropylen copolymers, fluorinated ethylene propylene copolymers, Polyfluorostyrene or polyvinyl carbazole can be used. The impregnating agent is preferably a conventional oil for oil-filled cables.

If the plastic material is of such a type, whose physical properties can be improved by treatment with high-energy radiation, the radiation can after the lamellar layering with the paper take place.

It can be assumed that the prestressed layer materials, as defined in the foregoing, better compatibility with impregnating agents of low viscosity than Have layer materials which are produced by other processes.

The plastic film is usually swollen and to a certain G-wheel by absorbing the oil swollen, etc. and this swelling is controlled in part by the resistance of the paper ribbons against elongation. This function is of greater importance in the outer parts of the dielectric, since inner parts are also retained or held in place by the superimposed strips of the outer parts Stress is greatest. In most cases it will therefore be advantageous to leave the dielectric off

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a number of different composite tapes so that that portion of the dielectric which formed by plastic material, with 'increasing distance' decreases from the cable ladder. The number of steps or levels * which is desired increases with the thickness of the dielectric wall and therefore with the operating voltage of the cable. Will For example, polypropylene is used as the plastic material and a normal low-viscosity cable oil is used as the impregnation agent ν, where the dielectric has a wall thickness of 10 mm, there are two steps or stages, and if the dielectric wall thickness is 25 mm, then three steps or stages will be desirable.

It was surprising to note that the dielectric loss angle of the entire dielectric varies with the thickness of the individual bands, even if the proportion of plastic material remains constant _o In the case of a dielectric, which is composed of bands each with a polypropylene film, on both surfaces of which a paper from half "of its thickness and is impregnated with a conventional oil for oil-filled cables (with a viscosity in the range of 12.5 - 15 centistokes at 2O ⁰ C), the power ^{factor at 85 0} G averages to 0.0007, when the total thickness of each band is 100 µm, but only to 0.0005 when it is 160 µm. ' It may therefore be desirable to use the thickest composite tapes that are mechanically acceptable.

Although it is generally preferable, at least at lower voltages, all of the dielectric from d'en mentioned Building composite ligaments can be beneficial be just part of the dielectric from such tapes to form, the remainder in such cases preferably being made up of paper tapes. For example, in the case of an execution

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for example the dielectric along its entire length having an inner portion of the composite tape and an outer portion of paper; and in another exemplary embodiment the composite tape can only do the restoration of the dielectric at junctions and end connections be used. It will usually be preferable to have the composite tape in joints or Always use end connections, whether all of the original dielectric or a part of it from the composite Tape exists, but the optimal layer thicknesses of the " Plastic and paper layers of the composite tape used in the joints and end connections can differ from the optimal layer thicknesses of the corresponding layers in the cable due to the different stress distribution.

The conductor shielding and / or dielectric shielding of the cable according to the invention are preferably formed from single or multiple layers of the lamellar tape, similar to that which is used to form the entire dielectric or etastiPart thereof, which is metalized accordingly and / or with carbon or another managerial ä the material is fed. Preferably all three layers of the laminate are loaded with conductive material, but in some cases, e.g. paper layers that adjoin the dielectric. The paper that is not loaded with conductive material is preferably loaded with aluminum oxide or another active material of the type already mentioned above.

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The invention is now based on one in the drawing illustrated embodiment described for a single-core oil-filled cable.

In the drawing, 1 is a steel band screw winding which forms a central oil line within the metallic conductor 2. A conductor shield 3, a dielectric 4, which is described in more detail below, and a dielectric shield 5 are applied to the conductor, the ^! Shields 3 and 5 are formed from metallized strips or from strips which, as already mentioned, are loaded or charged with conductive material. The cable is completed by a lead jacket 6, a bronze tape or some other pressure-resistant armouring 7 and a plastic outer jacket 8.

In a first embodiment of the cable shown, which is a 132 kV cable, the radial layer thickness of the dielectric 4 is 5.5 mm, corresponding to a Henn stress of 16 MV / m. The entire dielectric is made up of composite strips, which have 50 μm polypropylene, which is sandwiched between two layers of paper with a thickness of 25 Aim each. ,

In the second embodiment, which is a 220 kV cable is, the dielectric has three concentric, parts that each have a radial layer thickness of approximately 3.5 mm, v / o for each part consists of composite bands which have a layer of polypropylene sandwiched between two layers of paper. With the ligaments of the inner Partly the polypropylene layer is 80 / µm thick and every paper ice layer 10 / µm thick; with the ligaments of the intermediate part is the

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^0RIQINAL

· "9 -

Polypropylene layer 50 µm thick and each paper layer 25 µm thick; and "for the tapes of the outer part, the polypropylene layer is only 20 / µm thick and each paper layer is 40 / µm thick.

In the third exemplary embodiment, which is a 400 kV cable, the dielectric has four concentric parts, each of which has a radial layer thickness of approximately 6.25 mm. The three inner parts each consist of a composite. Ribbon, wherein the central polypropylene layers, layer thicknesses of 60, 40 and 20 / um, beginning with the innermost layer, i and each of the paper layers have a layer thickness to have each of 20, 40 and 75 /. The outer part is formed from tapes of ordinary cable insulating paper with a thickness of 250 µm.

In each of the three embodiments, the paper used in the composite belt is the preferred uncalendered electrical grade paper mentioned above, and the composite sheet material is prestressed by being made in the manner described above. The impregnating material in any case is a conventional cable oil for oil-filled cable with a petroleum-based viscosity 12.5 to 15 centistokes at 20 ⁰ C.

The invention also relates to modifications of the enclosed Claim 1 outlined embodiment and relates above all to all features of the invention, which in detail - or in combination - are disclosed in the entire description and drawing.

Claims

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Claims (9)

- ίο - Claims Electrical high-voltage cable with a metallic conductor, a lamellar dielectric, which surrounds the conductor and is impregnated with an insulating liquid which is kept under increased pressure, and ψ ' with a fluid-tight overall jacket, characterized by the combination of a dielectric, which at least is constructed of composite strips in part ,, which have a non-perforated plastic film ,, in which each major surface of a thin cellulose paper tape is bonded by a ■ Dicht® 'of less than 0.8 g / cm and high opacity, with a movable impregnating agent having a viscosity less than 57 centistokes at ⁰ C and 2Q '■ less than 11 centistokes at 6O ⁰ C. 2. Cable according to .Anspruch 1 _r characterized, that the lamellar dielectric at least two different A composite ligament bears, in such a way, that the portion of the Dielectric, which is formed by plastic, decreases with increasing distance from the cable holder. . . 3. Cable according to claim 1 or 2, characterized in that the paper tape made of an uncalendered paper electrical Grade of inter-fiber length consists, which is a density essentially equal to 0.7 'g / önr and a Gurley impermeable v ity of more than 10,000 seconds. 18 / 146Ö 4. Cable according to one of claims 1 to 3, characterized in that that the viscosity of the mobile impregnant is less than 25 centistokes at 20 ° C. 5. Cable according to one of claims 1 to 4, characterized in that that the density of the paper is less than 0.75 g / cm 6. Cable according to one of claims 1 to 5, characterized in that the composite strips of a prestressed | ten layer material exist. . 7. Cable according to one of claims 1 to 6, characterized in that that at least one of the paper layers is each of at least some of the active alumina or ribbons with another active metal oxide, hydrogenated metal oxide, hydroxide, carbonate or a basic carbonate, which sorptive abilities compared to those of aluminum oxide ;, has, is loaded or loaded. 8. Cable according to one of claims 1 to 7 »which is a conductor shield or a dielectric shield or both contains, characterized in that the or each shield ™ is formed from at least one layer of lamellar tape similar to that used for the said Dielectric or a Veil of the same to form, which is metallized in 3-talk manner and / or with conductive Kai.erial is loaded or loaded. 9. A method for producing the cable according to one of the Claims 1 to β, wherein the plastic material is of a Genus is whose physical properties by treatment ^109818/1468 can be improved with high energy radiation by the process step of irradiating the plastic layer after the lamellar layering together the paper. 109818/1468