EP0256340B1 - Isolation électrique - Google Patents

Isolation électrique Download PDF

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Publication number
EP0256340B1
EP0256340B1 EP87110609A EP87110609A EP0256340B1 EP 0256340 B1 EP0256340 B1 EP 0256340B1 EP 87110609 A EP87110609 A EP 87110609A EP 87110609 A EP87110609 A EP 87110609A EP 0256340 B1 EP0256340 B1 EP 0256340B1
Authority
EP
European Patent Office
Prior art keywords
weight
electrical insulation
polar
component
polymer blend
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
EP87110609A
Other languages
German (de)
English (en)
Other versions
EP0256340A1 (fr
Inventor
Peter Dr. Fischer
Hans-Joachim Dr. Henkel
Norbert Dr. Müller
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Siemens AG
Original Assignee
Siemens AG
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
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Publication of EP0256340A1 publication Critical patent/EP0256340A1/fr
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Publication of EP0256340B1 publication Critical patent/EP0256340B1/fr
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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Classifications

    • 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
    • H01B3/30—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances plastics; resins; waxes
    • H01B3/44—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances plastics; resins; waxes vinyl resins; acrylic resins

Definitions

  • the invention relates to electrical insulation based on polyolefins, in particular for cables and wires, for medium and high voltage from approximately 10 kV with an additive for retarding water trees.
  • ECT electrochemical treeing
  • water treeing processes that are particularly important with regard to the operational safety of plastic-insulated medium and high voltage cables, lead to the formation of tree-like structures, the so-called ECT structures.
  • the mechanism of ECT formation has not yet been clarified. In general, however, it is assumed that an electric field and the presence of a polar liquid, in particular water, are required for the formation of the ECT structures; the ECT structures are therefore also called water trees.
  • the initiation sites of the water trees always appear to be impurities, such as impurities, aggregated admixtures, cavities, gaps, cracks or interfaces, of which only a part leads to the formation of water trees.
  • the tree-like structures extend in the direction of the electrical field from the defects, which cannot be completely avoided in large-scale insulation.
  • ECT structures represent local changes in the insulation material, they can damage the insulation, especially with regard to the dielectric strength. Numerous attempts have therefore already been made to prevent or at least delay the growth of water trees. In particular, additives are added to the insulating layer.
  • the object of the invention is to design an electrical insulation of the type mentioned in such a way that it meets the requirements of practice in every respect, in particular an ECT-retarding effectiveness and low dielectric losses are sought.
  • the electrical insulation consists of an ethylene copolymer with a polar co-component or of a polymer blend of polyethylene and the ethylene copolymer, the proportion of the polar co-component in the copolymer or in the polymer blend being 1 to 5% by weight. is, and that it contains 0.1 to 1.5 wt .-% pyrogenic silica as an additive, based on the weight of the copolymer or the polymer blend.
  • the dielectric losses can be reduced - by using this special polyolefin - without adversely affecting the excellent ECT-retarding effect of the silica becomes. This is very surprising and could never have been foreseen.
  • Polyolefins serve as the basis for the known insulating materials, specifically in crosslinked or uncrosslinked form.
  • polyethylene and cross-linked polyethylene are used.
  • ethylene copolymers such as Ethylene-propylene copolymers (EPR), ethylene-vinyl acetate copolymers (EVA) and ethylene-alkyl acrylate copolymers (for example ethylene-ethyl acrylate and butyl acrylate copolymers), or ethylene-propylene-diene terpolymers and mixtures (blends) of these Ethylene copolymers and terpolymers with polyolefins, in particular polyethylene and polypropylene, can be used.
  • EPR Ethylene-propylene copolymers
  • EVA ethylene-vinyl acetate copolymers
  • ethylene-alkyl acrylate copolymers for example ethylene-ethyl acrylate and butyl acrylate copoly
  • ECT-retarding additives and the insulating materials just one combination would meet the requirements for ECT-retardation and low dielectric loss factor in a particularly outstanding manner, namely the combination of pyrogenic silica (as an additive for retarding water trees) and a special polyolefin.
  • This special polyolefin is an ethylene copolymer with a polar co-component or a polymer blend of polyethylene and such an ethylene copolymer.
  • the proportion of the polar co-component in the copolymer or in the polymer blend is in each case 1 to 5% by weight; this proportion is preferably 2 to 4% by weight.
  • a polymer blend When a polymer blend is used, it is preferably composed of 80 to 90% by weight of polyethylene and 10 to 20% by weight of the ethylene copolymer, the proportions of the two constituents of the mixture being 100% complementary.
  • the proportion of the ethylene copolymer is preferably approximately 15% by weight.
  • the ethylene copolymer can have a content of 10 to 45% by weight of polar co-component.
  • ethylene copolymer When using an ethylene copolymer alone, as already stated, it has a content of 1 to 5% by weight of the polar co-component. This proportion can also be realized in such a way that mixtures of ethylene copolymers with different polar co-component contents are used. The same applies to the ethylene copolymer in polymer blends.
  • the polar co-component of the ethylene copolymer must be sufficiently thermally and hydrolytically stable under the manufacturing and operating conditions of the electrical insulation according to the invention.
  • the polar co-component is therefore generally vinyl acetate, vinyl alcohol, acrylonitrile, an alkyl acrylate or an alkyl maleate.
  • the polar co-component of the ethylene copolymer is particularly advantageous methyl, ethyl or butyl acrylate.
  • Ethylene-butyl acrylate copolymers (EBA) are particularly preferred as the ethylene copolymer.
  • the fumed silica contained in the electrical insulation according to the invention is a synthetic product; it arises, for example, during the hydrolysis of silicon tetrachloride in a detonating gas flame (temperature: approx. 1000 ° C). Pyrogenic silica (chemical composition: Si0 2 ), which is in a highly dispersed, ie finely divided form, is characterized by the fact that it is not crystalline but X-ray amorphous.
  • the proportion of the ECT-retarding additive i.e. of the fumed silica in the electrical insulation according to the invention, as already stated, is 0.1 to 1.5% by weight, based on the weight of the polymer blend. This proportion is advantageously 0.3 to 1% by weight and preferably approximately 0.5% by weight.
  • the fumed silica is added to the insulating material.
  • the additives can also include the field-delimiting layers, i.e. the inner and / or outer conductive layer can be added.
  • the electrical insulation according to the invention can also be used in sleeves and fittings.
  • the polyolefins on which the insulating materials are based are generally crosslinked, but they can also be used in the uncrosslinked state. Crosslinking is preferably carried out peroxidically or by high-energy rays. Conventional additives, such as oxidation stabilizers, can also be added to the insulating materials.
  • LDPE high purity low density polyethylene
  • EBA ethylene butyl acrylate
  • polar co-component polar co-component
  • test results show that the plate test specimens containing pyrogenic silica do not have any ECT structures after the electrical stress, which is not the case for the test specimens without added silicic acid.
  • ECT retardation it is also important for electrical reasons that the dielectric losses and thus the tanö are as low as possible.
  • the electrical insulation according to the invention made of a special polyolefin containing pyrogenic silica both has low dielectric losses and effectively and permanently suppresses the formation of ECT.

Landscapes

  • Physics & Mathematics (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • Organic Insulating Materials (AREA)
  • Compositions Of Macromolecular Compounds (AREA)
  • Insulated Conductors (AREA)

Claims (6)

1. Isolant électrique à base de polyoléfine, notamment pour des câbles et des conducteurs, pour la moyenne tension et la haute tension à partir de 10 kV environ, comprenant un additif pour retarder l'arborescence d'eau, caractérisé en ce qu'il est constitué d'un copolymère d'éthylène à coconstituant polaire ou d'un mélange de polymères, constitué de polyéthylène et du copolymère d'éthylène, la proportion du coconstituant polaire dans le copolymère ou dans le mélange de polymères étant de 1 à 5% en poids, et il contient comme additif de 0,1 à 1,5% en poids d'acide silicique pyrogène rapporté au poids du copolymère ou du mélange de polymères.
2. Isolant électrique suivant la revendication 1, caractérisé en ce qu'il est constitué d'un mélange de polymères, constitué de 80 à 90 % en poids de polyéthylène et de 20 à à 10 % en poids d'un copolymère d'éthylène à coconstituant polaire.
3. Isolant électrique suivant la revendication 2, caractérisé en ce que la proportion du copolymère d'éthylène représente 15 % en poids environ du mélange de polymère.
4. Isolant électrique suivant l'une des revendications 1 à 3, caractérisé en ce que la proportion de l'additif est de 0,3 à 1% en poids, et notamment de 0,5% en poids environ.
5. Isolant électrique suivant l'une des revendications 1 à 4, caractérisé en ce que le coconstituant polaire du copolymère d'éthylène est de l'acétate de vinyle, de l'alcool vinylique, de l'acrylonitrile, un acrylate d'alcoyle, ou un maléate d'alcoyle.
6. Isolant électrique suivant la revendication 5, caractérisé en ce que le coconstituant polaire est l'acrylate de méthyle, l'acrylate d'éthyle ou l'acrylate de butyle.
EP87110609A 1986-08-04 1987-07-22 Isolation électrique Expired - Lifetime EP0256340B1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE3626409 1986-08-04
DE3626409 1986-08-04

Publications (2)

Publication Number Publication Date
EP0256340A1 EP0256340A1 (fr) 1988-02-24
EP0256340B1 true EP0256340B1 (fr) 1990-06-13

Family

ID=6306687

Family Applications (1)

Application Number Title Priority Date Filing Date
EP87110609A Expired - Lifetime EP0256340B1 (fr) 1986-08-04 1987-07-22 Isolation électrique

Country Status (3)

Country Link
EP (1) EP0256340B1 (fr)
JP (1) JPS6343209A (fr)
DE (1) DE3763270D1 (fr)

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS63226815A (ja) * 1987-03-16 1988-09-21 三菱電線工業株式会社 電気絶縁性組成物
JPS63226814A (ja) * 1987-03-16 1988-09-21 三菱電線工業株式会社 電気絶縁性組成物

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2737430C2 (de) * 1977-08-19 1983-03-17 Licentia Patent-Verwaltungs-Gmbh, 6000 Frankfurt Polyolefinisolierung mit einem Spannungsstabilisator
DE2909498A1 (de) * 1979-03-10 1980-09-18 Basf Ag Flammhemmende thermoplastische formmassen
WO1983001415A1 (fr) * 1981-10-26 1983-04-28 Gen Electric Fil a retardement de flamme avec resistance isolante elevee
DE3318988A1 (de) * 1983-05-25 1984-11-29 Siemens AG, 1000 Berlin und 8000 München Elektrische isolierungen
DE3318963A1 (de) * 1983-05-25 1984-11-29 Siemens AG, 1000 Berlin und 8000 München Stabilisierung organischer polymermaterialien

Also Published As

Publication number Publication date
DE3763270D1 (de) 1990-07-19
EP0256340A1 (fr) 1988-02-24
JPS6343209A (ja) 1988-02-24

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