GB2187589A - High voltage cable - Google Patents
High voltage cable Download PDFInfo
- Publication number
- GB2187589A GB2187589A GB08704814A GB8704814A GB2187589A GB 2187589 A GB2187589 A GB 2187589A GB 08704814 A GB08704814 A GB 08704814A GB 8704814 A GB8704814 A GB 8704814A GB 2187589 A GB2187589 A GB 2187589A
- Authority
- GB
- United Kingdom
- Prior art keywords
- tape
- polymer
- electric cable
- silyl modified
- layers
- 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.)
- Granted
Links
- 229920001577 copolymer Polymers 0.000 claims abstract description 52
- 125000001181 organosilyl group Chemical group [SiH3]* 0.000 claims abstract description 35
- -1 unsaturated silane compound Chemical class 0.000 claims abstract description 24
- 239000004020 conductor Substances 0.000 claims abstract description 23
- 238000009413 insulation Methods 0.000 claims abstract description 16
- 239000005977 Ethylene Substances 0.000 claims abstract description 14
- VGGSQFUCUMXWEO-UHFFFAOYSA-N Ethene Chemical compound C=C VGGSQFUCUMXWEO-UHFFFAOYSA-N 0.000 claims abstract description 13
- 239000006229 carbon black Substances 0.000 claims abstract description 5
- NKSJNEHGWDZZQF-UHFFFAOYSA-N ethenyl(trimethoxy)silane Chemical compound CO[Si](OC)(OC)C=C NKSJNEHGWDZZQF-UHFFFAOYSA-N 0.000 claims abstract description 4
- 229920000092 linear low density polyethylene Polymers 0.000 claims abstract description 4
- 239000004707 linear low-density polyethylene Substances 0.000 claims abstract description 4
- 239000010410 layer Substances 0.000 claims description 39
- 239000003054 catalyst Substances 0.000 claims description 19
- 238000009833 condensation Methods 0.000 claims description 16
- 230000005494 condensation Effects 0.000 claims description 16
- SCPYDCQAZCOKTP-UHFFFAOYSA-N silanol Chemical compound [SiH3]O SCPYDCQAZCOKTP-UHFFFAOYSA-N 0.000 claims description 15
- 239000004698 Polyethylene Substances 0.000 claims description 7
- 229920000578 graft copolymer Polymers 0.000 claims description 7
- 229920000573 polyethylene Polymers 0.000 claims description 7
- 229920001038 ethylene copolymer Polymers 0.000 claims description 5
- 239000000463 material Substances 0.000 claims description 5
- 238000004519 manufacturing process Methods 0.000 claims description 4
- 150000004756 silanes Chemical class 0.000 claims description 3
- NOZAQBYNLKNDRT-UHFFFAOYSA-N [diacetyloxy(ethenyl)silyl] acetate Chemical compound CC(=O)O[Si](OC(C)=O)(OC(C)=O)C=C NOZAQBYNLKNDRT-UHFFFAOYSA-N 0.000 claims description 2
- FWDBOZPQNFPOLF-UHFFFAOYSA-N ethenyl(triethoxy)silane Chemical compound CCO[Si](OCC)(OCC)C=C FWDBOZPQNFPOLF-UHFFFAOYSA-N 0.000 claims description 2
- WOXXJEVNDJOOLV-UHFFFAOYSA-N ethenyl-tris(2-methoxyethoxy)silane Chemical compound COCCO[Si](OCCOC)(OCCOC)C=C WOXXJEVNDJOOLV-UHFFFAOYSA-N 0.000 claims description 2
- 239000002356 single layer Substances 0.000 claims description 2
- 239000011248 coating agent Substances 0.000 claims 1
- 238000000576 coating method Methods 0.000 claims 1
- 229910000077 silane Inorganic materials 0.000 abstract description 7
- BLRPTPMANUNPDV-UHFFFAOYSA-N Silane Chemical compound [SiH4] BLRPTPMANUNPDV-UHFFFAOYSA-N 0.000 abstract description 5
- 230000005540 biological transmission Effects 0.000 abstract description 4
- 239000002480 mineral oil Substances 0.000 abstract description 2
- 235000010446 mineral oil Nutrition 0.000 abstract description 2
- 229920001083 polybutene Polymers 0.000 abstract description 2
- 238000000034 method Methods 0.000 description 13
- 239000003921 oil Substances 0.000 description 6
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 6
- 229920002678 cellulose Polymers 0.000 description 5
- 239000001913 cellulose Substances 0.000 description 5
- 239000000203 mixture Substances 0.000 description 5
- QTBSBXVTEAMEQO-UHFFFAOYSA-N Acetic acid Chemical group CC(O)=O QTBSBXVTEAMEQO-UHFFFAOYSA-N 0.000 description 4
- 238000010276 construction Methods 0.000 description 4
- 239000003999 initiator Substances 0.000 description 4
- 150000003254 radicals Chemical class 0.000 description 4
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 description 3
- 229920000642 polymer Polymers 0.000 description 3
- 239000011135 tin Substances 0.000 description 3
- 229910052718 tin Inorganic materials 0.000 description 3
- FERIUCNNQQJTOY-UHFFFAOYSA-N Butyric acid Chemical compound CCCC(O)=O FERIUCNNQQJTOY-UHFFFAOYSA-N 0.000 description 2
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 2
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 2
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 2
- JUJWROOIHBZHMG-UHFFFAOYSA-N Pyridine Chemical compound C1=CC=NC=C1 JUJWROOIHBZHMG-UHFFFAOYSA-N 0.000 description 2
- UKLDJPRMSDWDSL-UHFFFAOYSA-L [dibutyl(dodecanoyloxy)stannyl] dodecanoate Chemical compound CCCCCCCCCCCC(=O)O[Sn](CCCC)(CCCC)OC(=O)CCCCCCCCCCC UKLDJPRMSDWDSL-UHFFFAOYSA-L 0.000 description 2
- 239000000654 additive Substances 0.000 description 2
- 125000003545 alkoxy group Chemical group 0.000 description 2
- 150000007942 carboxylates Chemical class 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 2
- JQVDAXLFBXTEQA-UHFFFAOYSA-N dibutylamine Chemical compound CCCCNCCCC JQVDAXLFBXTEQA-UHFFFAOYSA-N 0.000 description 2
- 239000012975 dibutyltin dilaurate Substances 0.000 description 2
- 125000001183 hydrocarbyl group Chemical group 0.000 description 2
- 230000001965 increasing effect Effects 0.000 description 2
- 150000007522 mineralic acids Chemical class 0.000 description 2
- 150000007524 organic acids Chemical class 0.000 description 2
- 229920000620 organic polymer Polymers 0.000 description 2
- 239000003707 silyl modified polymer Substances 0.000 description 2
- 238000005809 transesterification reaction Methods 0.000 description 2
- 239000004711 α-olefin Substances 0.000 description 2
- BMVXCPBXGZKUPN-UHFFFAOYSA-N 1-hexanamine Chemical class CCCCCCN BMVXCPBXGZKUPN-UHFFFAOYSA-N 0.000 description 1
- LBLYYCQCTBFVLH-UHFFFAOYSA-N 2-Methylbenzenesulfonic acid Chemical compound CC1=CC=CC=C1S(O)(=O)=O LBLYYCQCTBFVLH-UHFFFAOYSA-N 0.000 description 1
- URDOJQUSEUXVRP-UHFFFAOYSA-N 3-triethoxysilylpropyl 2-methylprop-2-enoate Chemical compound CCO[Si](OCC)(OCC)CCCOC(=O)C(C)=C URDOJQUSEUXVRP-UHFFFAOYSA-N 0.000 description 1
- ADBORBCPXCNQOI-UHFFFAOYSA-N 3-triethoxysilylpropyl acetate Chemical compound CCO[Si](OCC)(OCC)CCCOC(C)=O ADBORBCPXCNQOI-UHFFFAOYSA-N 0.000 description 1
- XDQWJFXZTAWJST-UHFFFAOYSA-N 3-triethoxysilylpropyl prop-2-enoate Chemical compound CCO[Si](OCC)(OCC)CCCOC(=O)C=C XDQWJFXZTAWJST-UHFFFAOYSA-N 0.000 description 1
- FZTPAOAMKBXNSH-UHFFFAOYSA-N 3-trimethoxysilylpropyl acetate Chemical compound CO[Si](OC)(OC)CCCOC(C)=O FZTPAOAMKBXNSH-UHFFFAOYSA-N 0.000 description 1
- 239000004215 Carbon black (E152) Substances 0.000 description 1
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- OFOBLEOULBTSOW-UHFFFAOYSA-N Propanedioic acid Natural products OC(=O)CC(O)=O OFOBLEOULBTSOW-UHFFFAOYSA-N 0.000 description 1
- 235000021355 Stearic acid Nutrition 0.000 description 1
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 1
- HCHKCACWOHOZIP-UHFFFAOYSA-N Zinc Chemical compound [Zn] HCHKCACWOHOZIP-UHFFFAOYSA-N 0.000 description 1
- ISKQADXMHQSTHK-UHFFFAOYSA-N [4-(aminomethyl)phenyl]methanamine Chemical compound NCC1=CC=C(CN)C=C1 ISKQADXMHQSTHK-UHFFFAOYSA-N 0.000 description 1
- HRIMTTNYSCTIDV-UHFFFAOYSA-L [dibutyl(hexadecanoyloxy)stannyl] hexadecanoate Chemical compound CCCCCCCCCCCCCCCC(=O)O[Sn](CCCC)(CCCC)OC(=O)CCCCCCCCCCCCCCC HRIMTTNYSCTIDV-UHFFFAOYSA-L 0.000 description 1
- YVHDRFKHKGNLNW-UHFFFAOYSA-L [dibutyl(octadecanoyloxy)stannyl] octadecanoate Chemical compound CCCCCCCCCCCCCCCCCC(=O)O[Sn](CCCC)(CCCC)OC(=O)CCCCCCCCCCCCCCCCC YVHDRFKHKGNLNW-UHFFFAOYSA-L 0.000 description 1
- NBJODVYWAQLZOC-UHFFFAOYSA-L [dibutyl(octanoyloxy)stannyl] octanoate Chemical compound CCCCCCCC(=O)O[Sn](CCCC)(CCCC)OC(=O)CCCCCCC NBJODVYWAQLZOC-UHFFFAOYSA-L 0.000 description 1
- RMKZLFMHXZAGTM-UHFFFAOYSA-N [dimethoxy(propyl)silyl]oxymethyl prop-2-enoate Chemical compound CCC[Si](OC)(OC)OCOC(=O)C=C RMKZLFMHXZAGTM-UHFFFAOYSA-N 0.000 description 1
- XQBCVRSTVUHIGH-UHFFFAOYSA-L [dodecanoyloxy(dioctyl)stannyl] dodecanoate Chemical compound CCCCCCCCCCCC(=O)O[Sn](CCCCCCCC)(CCCCCCCC)OC(=O)CCCCCCCCCCC XQBCVRSTVUHIGH-UHFFFAOYSA-L 0.000 description 1
- 239000011358 absorbing material Substances 0.000 description 1
- 150000001252 acrylic acid derivatives Chemical class 0.000 description 1
- 125000001931 aliphatic group Chemical group 0.000 description 1
- 125000000217 alkyl group Chemical group 0.000 description 1
- 239000003963 antioxidant agent Substances 0.000 description 1
- 238000007664 blowing Methods 0.000 description 1
- 125000002843 carboxylic acid group Chemical group 0.000 description 1
- 230000015556 catabolic process Effects 0.000 description 1
- 239000010941 cobalt Substances 0.000 description 1
- 229910017052 cobalt Inorganic materials 0.000 description 1
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 239000000110 cooling liquid Substances 0.000 description 1
- 238000004132 cross linking Methods 0.000 description 1
- JQZRVMZHTADUSY-UHFFFAOYSA-L di(octanoyloxy)tin Chemical compound [Sn+2].CCCCCCCC([O-])=O.CCCCCCCC([O-])=O JQZRVMZHTADUSY-UHFFFAOYSA-L 0.000 description 1
- PNOXNTGLSKTMQO-UHFFFAOYSA-L diacetyloxytin Chemical compound CC(=O)O[Sn]OC(C)=O PNOXNTGLSKTMQO-UHFFFAOYSA-L 0.000 description 1
- 150000002148 esters Chemical group 0.000 description 1
- 150000002170 ethers Chemical class 0.000 description 1
- 125000004494 ethyl ester group Chemical group 0.000 description 1
- 150000003947 ethylamines Chemical class 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 229920001903 high density polyethylene Polymers 0.000 description 1
- 239000004700 high-density polyethylene Substances 0.000 description 1
- 229930195733 hydrocarbon Natural products 0.000 description 1
- 238000011065 in-situ storage Methods 0.000 description 1
- 230000001939 inductive effect Effects 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 239000011133 lead Substances 0.000 description 1
- GIWKOZXJDKMGQC-UHFFFAOYSA-L lead(2+);naphthalene-2-carboxylate Chemical compound [Pb+2].C1=CC=CC2=CC(C(=O)[O-])=CC=C21.C1=CC=CC2=CC(C(=O)[O-])=CC=C21 GIWKOZXJDKMGQC-UHFFFAOYSA-L 0.000 description 1
- 229920001684 low density polyethylene Polymers 0.000 description 1
- 239000004702 low-density polyethylene Substances 0.000 description 1
- VZCYOOQTPOCHFL-UPHRSURJSA-N maleic acid Chemical compound OC(=O)\C=C/C(O)=O VZCYOOQTPOCHFL-UPHRSURJSA-N 0.000 description 1
- 239000011976 maleic acid Substances 0.000 description 1
- 239000000155 melt Substances 0.000 description 1
- 150000002736 metal compounds Chemical class 0.000 description 1
- GEMHFKXPOCTAIP-UHFFFAOYSA-N n,n-dimethyl-n'-phenylcarbamimidoyl chloride Chemical compound CN(C)C(Cl)=NC1=CC=CC=C1 GEMHFKXPOCTAIP-UHFFFAOYSA-N 0.000 description 1
- 229910052759 nickel Inorganic materials 0.000 description 1
- 150000002825 nitriles Chemical class 0.000 description 1
- QIQXTHQIDYTFRH-UHFFFAOYSA-N octadecanoic acid Chemical compound CCCCCCCCCCCCCCCCCC(O)=O QIQXTHQIDYTFRH-UHFFFAOYSA-N 0.000 description 1
- OQCDKBAXFALNLD-UHFFFAOYSA-N octadecanoic acid Natural products CCCCCCCC(C)CCCCCCCCC(O)=O OQCDKBAXFALNLD-UHFFFAOYSA-N 0.000 description 1
- 235000005985 organic acids Nutrition 0.000 description 1
- 125000000962 organic group Chemical group 0.000 description 1
- 150000001451 organic peroxides Chemical class 0.000 description 1
- 125000000864 peroxy group Chemical group O(O*)* 0.000 description 1
- UMJSCPRVCHMLSP-UHFFFAOYSA-N pyridine Natural products COC1=CC=CN=C1 UMJSCPRVCHMLSP-UHFFFAOYSA-N 0.000 description 1
- 239000002516 radical scavenger Substances 0.000 description 1
- 150000004819 silanols Chemical class 0.000 description 1
- 239000002002 slurry Substances 0.000 description 1
- 239000008117 stearic acid Substances 0.000 description 1
- 239000001117 sulphuric acid Substances 0.000 description 1
- 235000011149 sulphuric acid Nutrition 0.000 description 1
- 239000000725 suspension Substances 0.000 description 1
- VXUYXOFXAQZZMF-UHFFFAOYSA-N titanium(IV) isopropoxide Chemical compound CC(C)O[Ti](OC(C)C)(OC(C)C)OC(C)C VXUYXOFXAQZZMF-UHFFFAOYSA-N 0.000 description 1
- VZCYOOQTPOCHFL-UHFFFAOYSA-N trans-butenedioic acid Natural products OC(=O)C=CC(O)=O VZCYOOQTPOCHFL-UHFFFAOYSA-N 0.000 description 1
- YUYCVXFAYWRXLS-UHFFFAOYSA-N trimethoxysilane Chemical compound CO[SiH](OC)OC YUYCVXFAYWRXLS-UHFFFAOYSA-N 0.000 description 1
- 229920001567 vinyl ester resin Polymers 0.000 description 1
- 125000000391 vinyl group Chemical group [H]C([*])=C([H])[H] 0.000 description 1
- 239000002982 water resistant material Substances 0.000 description 1
- 229910052725 zinc Inorganic materials 0.000 description 1
- 239000011701 zinc Substances 0.000 description 1
- CHJMFFKHPHCQIJ-UHFFFAOYSA-L zinc;octanoate Chemical compound [Zn+2].CCCCCCCC([O-])=O.CCCCCCCC([O-])=O CHJMFFKHPHCQIJ-UHFFFAOYSA-L 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
- H01B9/00—Power cables
- H01B9/02—Power cables with screens or conductive layers, e.g. for avoiding large potential gradients
- H01B9/027—Power cables with screens or conductive layers, e.g. for avoiding large potential gradients composed of semi-conducting layers
-
- 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
- H01B3/441—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 from alkenes
Landscapes
- Physics & Mathematics (AREA)
- Spectroscopy & Molecular Physics (AREA)
- Organic Insulating Materials (AREA)
Abstract
An electrical cable suitable for transmission of high voltage comprises a central core conductor coated substantially coaxially with a semi-conductive inner shielding layer, an insulation layer and an outer shielding layer, the insulation layer being formed from overlapping layers of tape comprising a silyl modified (co) polymer. The copolymer may be made by copolymerising ethylene with a hydrolysable unsaturated silane compound e.g. vinyl trimethoxy silane, or grafting the hydrolysable silane onto a linear low density polyethylene. The inner layers of tape may be thinner than the outer layers. Optionally the tape is impregnated with polybutene or mineral oil. The shielding layers are formed by incorporating carbon black in a silyl modified (co)polymer.
Description
SPECIFICATION
High voltage cable
The present invention relates to an electrical cable construction and in particular to an electrical cable suitable for the transmission of high voltage.
The construction of insulated electrical conductors for use in the transmission of high voltage electric current is well known. Such cables generally comprise a central core conductor surrounded coaxially by a semi-conductive shielding layer, an insulation layer and an outer shielding layer. The cable may also be provided with armoured covering and additional layers to provide, for example, weather protection or increased mechanical strength.
Generally, the core conductor has a central duct for the circulation of cooling liquid e.g.
oil. The core conductor is therefore usually of tubular construction. The conductor may, for example, comprise a continuous pipe of a suitable conducting material, e.g. copper, but preferably comprises a plurality of segments each of which segments is made of strands, e.g. copper wire, and is shaped such that when the segments are brought together they provide a substantially cylindrical conductor having a central oil duct.
The material most commonly used to insulate high voltage electrical cable is cellulose paper which is impregnated with oil. The paper is generally used in the form of tape which is wound about the core conductor in overlapping layers to provide the thickness of insulation required. High voltage cables insulated with cellulose paper tape have relatively high dielectric loss and must be oil-cooled.
The specific inductive capacity (dielectric constant) of oil-impregnated cellulose paper is approximately 3.5 and the power factor is approximately 0.20.
It is an object of the present invention to provide improved high voltage electrical cables, particularly high voltage cable, for long-distance transmission, by using a silyl modified (co) polymer tape in place of the conventional cellulose paper tape to insulate the core conductor. High voltage cables according to the present invention may not require the core conductor to be cooled by cooling oil in a central oil duct. Cables according to the present invention are particularly suitable for ver high voltages e.g. in excess of 750 kV.
Thus according to the present invention an electric cable comprising a central core conductor surrounded substantially coaxially and in sequential order by an inner semi-conductive shielding layer, an insulation layer and an outer shielding layer is characterised in that the insulation layer is formed from overlapping layers of tape essentially comprising crosslinked silyl modified (co) polymer.
It is known that organic polymers containing hydrolysable silane groups can be cross-linked by the action of H2O, preferably in the presence of a silanol condensation catalyst.
In the present invention the silyl modified (cho) polymer is preferably a silyl modified ethylene (co) polymer having hydrolysable silane groups and can be, for example, a polymer prepared by copolymerising monomeric material comprising ethylene with an unsaturated silane compound having hydrolysable groups or can be, for example, a graft polymer prepared by grafting an unsaturated silane compound having hydrolysable silane groups onto a polyethylene or an ethylene copolymer.
Preferred silyl modified (co) polymers are copolymers prepared by copolymerising ethylene, optionally together with one or more alphaolefins, vinyl esters, alkyl(meth)acrylates, unsaturated nitriles or unsaturated ethers with an unsaturated silane compound in the presence of a free radical initiator. Also preferred are graft polymers prepared by grafting an unsaturated silane compound onto polyethylene or onto a copolymer of ethylene with one or more alpha-olefins by heating the polyethylene, or copolymer of ethylene, with the unsaturated silane compound in the presence of a free radical initiator, for example, an organic peroxide. The polyethylene or copolymer of ethylene can comprise, for example, low density polyethylene, low density ethylene hydrocarbon copolymers (e.g. LLDPE) or high density polyethylene.The graft-copolymerisation method forms the basis of the known 'SlO- PLAS" commercial technique for making cross-linkable ethylene/silane copolymers.
(SIOPLAS is a Registered Trade Mark).
The silyl modified (co) polymer can be formed "in situ" by grafting an unsaturated silane compound onto polyethylene or onto a copolymer of ethylene in the presence of a free radical initiator and optionally in the presence of a silanol condensation catalyst. This method forms the basis of the known singlestep "MONOSIL" process. (MONOSIL is a
Registered Trade Mark). In this process, the grafting reaction is performed simultaneously with the fabrication of the polymeric article, for example, by feeding the organic polymer, the unsaturated silane compound, the radical initiator and silanol condensation catalyst (optionally with conventional additives) to an extruder wherein the grafting reaction occurs and a cross-linkable product is extruded e.g.
through a film-flowing die.
The silane compound copolymerised with the ethylene or graft copolymerised with the polyethylene or copolymer of ethylene is preferably a compound having the general formula R1SiR2mY3m wherein R' represents an ethylenically unsaturated hydrocarbyl or hydrocarbyloxy group; R2 represents an aliphatic saturated hydrocarbyl group; Y represents a hydrolysable organic group; m represents 0, 1 or 2. Preferred unsaturated silane compounds for use in making the copolymer or graft copolymer are vinyl trimethoxy silane, vinyl triethoxy silane, vinyl tris (methoxy ethoxy) silane and vinyl triacetoxy silane.
Another method for forming silyl modified (co) polymers which can be employed in the composition of the present invention is the known "transesterification" method. In this method, for example, the alkoxy groups present in an ethylene/alkoxy (meth) acrylate copolymer can be "ester exchanged" or replaced by a silane substituent bearing hydrolysable groups by reacting the copolymer with a suitable silane compound in the presence of a catalyst (for example titanium tetraisopropylate). Examples of suitable silane compounds are acetoxypropyl trimethoxy silane, acetoxypropyl triethoxy silane, methyacryloxypropyl trimethoxy silane, acryloxypropyl trimethoxy silane, methacryloxypropyl triethoxy silane and acryloxypropyl triethoxy silane.The transesterification method can also be used to prepare silyl modified copolymers by reacting an ethylene/vinyl acetate copolymer with a suitable silane compound bearing hydrolysable groups and having esterified carboxylic acid groups which exchange with the acetate groups on the copolymer. A suitable silane compound is 4-[tri(m)ethoxysilyl]butanoic acid(m)ethyl ester.
The silyl modified (co) polymer employed in the present invention is preferably a copolymer or a graft copolymer containing from 0.1 to 10% by weight, more preferably 0.5 to 5% by weight of copolymerised units of the silane compound. Preferably the silyl modified (co) polymer has a melt index (ISO1133, 1900C, 2.16 kg load) of 0.02 to 5 g/10 minutes.
A particularly suitable silyl modified (co) polymer comprises a graft copolymer prepared by grafting an unsaturated silane compound e.g. vinyl trimethoxy silane onto a linear low density polyethylene in the presence of a peroxy catalyst and a silanol condensation catalyst.
For further details of silyl modified polymers suitable for use in the present invention reference may be made to GB-A-2028831, GB-A-2039513, GB-A-1357549, GB-A-1415194, GB-A-1286460,
GB-A-1234034 and US-A-3225018.
Preferably, the cross-linkable silyl modified (co) polymer from which the tape is made contains a silanol condensation catalyst. Any of the silanol condensation catalysts known in the art for cross-linking silyl modified (co) polymers can be suitably employed in the present invention. Examples of suitable classes of silanol condensation catalysts are organic and inorganic acids and alkalis and metal compounds, for example complexes or carboxylates of lead, cobalt, iron, nickel, zinc or tin.
Specific examples of the silanol condensation catalyst are dibutyl tin dilaurate, dibutyl tin diacetate, dibutyl tin dioctoate, stannous acetate, stannous caprylate, lead naphthenate, zinc caprylate, cobalt naphthenate; ethylamines, dibutylamine, hexylamines, pyridine; inorganic acids such as sulphuric acid, hydrochloric acid; and organic acids such as toluenesulphonic acid, acetic acid, stearic acid and maleic acid. Carboxylates of tin are preferred. Particularly preferred silanol condensation catalysts are dialkyl tin dicarboxylates, for example dibutyl tin dilaurate, dibutyl tin dipalmitate, dibutyl tin distearate and dioctyl tin dilaurate.
The quantity of silanol condensation catalyst employed in the cross-linkable silyl modified (co) polymer tape is suitable in the range 0.001 to 3.0 moles, preferably in the range from 0.003 to 0.05 moles per mole of silyl units in the silyl modified (co) polymer. Generally, the quantity of the catalyst to be blended into the composition is in the range 0.001 to 10% by weight, preferably 0.01 to 5% by weight most preferably 0.03 to 3% by weight, relative to the quantity of the silyl modified (co) polymer.
The silyl modified polymers may be made into tape using conventional methods and apparatus. For example, the known blown film or cast film processes may be used to make film from the cross-linkable silyl modified (co) polymers which is then cut into tape. Conventional additives such as antioxidants may be included in the film composition. The tape thickness is preferably from 20 to 200 mm.
The silyl modified (co) polymer tape suitable for use in the present invention can be a laminate comprising layers of more than one silyl modified (co) polymer or can be a laminate comprising at least one layer comprising a silyl modified (co) polymer and at least one layer of another polymeric material. Preferably, however, the sily modified (co) polymer tape is in the form of a monolayer. The present invention does not include laminates with one or more layers of conventional cellulose paper insulation.
High voltage cables according to the present invention may be of conventional construction except that the conventional paper tape insulation is replaced by the sily modified (co) polymer tape. However as indicated hereinabove the high voltage cable according to the present invention may not require a cental oil duct.
In general, the risk of a polymer tape containing imperfections increases with increasing tape thickness. Thus, in order to provide improved breakdown resistance, the cable is preferably insulated with relatively thin tape, at least in the region close to the core conductor (i.e. the inner layers). However, thicker tape will generally be easier to handle and so the outer layers of tape may be relatively thick. A cable according to the present invention may therefore be insulated with cross-linked silyl modified ethylene (co) polymer tape which is, for example, about 50 microns thick in the region close to the core conductor while at a greater radial distance from the core conductor, the tape thickness is about 100 microns.
The semi-conductive shielding layers applied about the conductor and overlying the insulation, may be made from conventional material or may also be formed from sily modified (co) polymer tape which has been rendered semiconductive by the inclusion in the composition of an electrically conductive material. The employment of carbon black in semi-conductive shielding compositions is well known in the art and any such carbon black in any suitable form can be employed in the sily modified (co) polyme tapes suitable for use in the present invention. Typically a semi-conductive shielding layer based on a silyl modified (co) polymer would require from 5 to 50% by weight of carbon black.
The present invention includes a method of manufacturing an electrical cable which method comprises covering an electrical core conductor with sequential layers comprising an inner semi-conductive shielding layer, an insulation layer and an outer semi-conductive shielding layer, the method being characterised in that the insulation layer is formed by overlapping layers of tape essentially comprising a cross-linked or cross-linkable silyl modified (co) polymer.
If the cable according to the present invention is manufactured using a cross-linkable silyl modified ethylene (co) polymer tape, the tape can be cross-linked by exposing the cable to water, steam or moist air, preferably in the presence of a silanol condensation catalyst.
The cable can, for example, be cross-linked by contacting it with an aqueous slurry or suspension of a silanol condensation catalyst.
However, as indicated hereinabove, the silyl modified(co) polymer from which the tape is manufactured preferably contains a silanol condensation catalyst. The cable according to the present invention can also be manufactured using cross-linked silyl modified (co) polymer tape. The tape may be cross-linked by exposing the tape or the film from which the tape is cut to water, steam or moist air, preferably in the presence of a silanol condensation catalyst. If the film from which the tape is cut is produced by the blown film process, it may be possible to at least partially cross-link the film by introducing water vapour or moist air into the bubble during the blowing.
Tapes of cross-linkable or cross-linked silyl modified (co) polymer have good mechanical properties which enable the tape to be tightly wrapped about the conductor. In order to improve the water resistance of the finished cable, the (co) polymer silyl modified tape can contain a suitable water scavenger and/or can be coated with a water absorbing material or water-resistant material. For example, the tape may be passed through a bath of polybutene or electrical grade mineral oil prior to being wrapped about the conductor.
Claims (10)
1. An electric cable comprising a central core conductor surrounded substantially coaxially and in sequential order by a semi-conductive inner shielding layer, an insulation layer and an outer shielding layer, characterised in that the insulation layer is formed from overlapping layers of tape essentially comprising crosslinked silyl modified (co) polymer.
2. An electric cable as claimed in claim 1 in which the silyl modified (co) polymer is a copolymer prepared by copolymerising monomeric material comprising ethylene with a hydrolysable unsaturated silane compound or is a graft polymer prepared by grafting a hydrolysable unsaturated silane compound onto a polyethylene or ethylene copolymer.
3. An electric cable as claimed in claim 1 or claim 2 in which the silyl modified (co) polymer comprises a graft copolymer prepared by grafting a hydrolysable unsaturated silane onto a linear low density polyethylene.
4. An electric cable as claimed in any one of claims 1 to 3 in which the hydrolysable unsaturated silane compound is vinyl trimethoxy silane, vinyl triethoxy silane, vinyl tris (methoxy, ethoxy) silane and vinyl triacetoxy silane.
5. An electric cable as claimed in any one of claims 1 to 4 in which the tape contains a silanol condensation catalyst.
6. An electric cable as claimed in any one of claims 1 to 5 in which the tape is a single layer of silyl modified (co) polymer.
7. An electric cable as claimed in any one of claims 1 to 6 in which the inner layers of tape closer to the core conductor are relatively thin and the outer layers of tape are relatively thick.
8. An electric cable as claimed in any one of claims 1 to 7 in which the semi-conductive shielding layers are formed from tape comprising silyl modified (co) polymer and an electrically conducting carbon black.
9. A method of manufacturing an electric cable comprising coating a core conductor with sequential layers comprising an inner semi-conductive shielding layer, an insulation layer and an outer shielding layer, characterised in that the insulation is formed by overlapping layers of tape essentially comprising a crosslinked or crosslinkable silyl modified (co) polymer.
10. A method of manufacturing an electric cable as claimed in claim 9 in which the insulation layer is formed by overlapping layers of tape essentially comprising a crosslinkable silyl modified (co) polymer and is subsequently crosslinked by exposure to H2O, preferably in the presence of a silanol condensation catalyst.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB868605242A GB8605242D0 (en) | 1986-03-04 | 1986-03-04 | High voltage cable |
Publications (3)
| Publication Number | Publication Date |
|---|---|
| GB8704814D0 GB8704814D0 (en) | 1987-04-08 |
| GB2187589A true GB2187589A (en) | 1987-09-09 |
| GB2187589B GB2187589B (en) | 1989-11-22 |
Family
ID=10593978
Family Applications (2)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB868605242A Pending GB8605242D0 (en) | 1986-03-04 | 1986-03-04 | High voltage cable |
| GB8704814A Expired GB2187589B (en) | 1986-03-04 | 1987-03-02 | High voltage cable |
Family Applications Before (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB868605242A Pending GB8605242D0 (en) | 1986-03-04 | 1986-03-04 | High voltage cable |
Country Status (1)
| Country | Link |
|---|---|
| GB (2) | GB8605242D0 (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5460886A (en) * | 1988-12-16 | 1995-10-24 | Sumitomo Electric Industries, Ltd. | DC high-voltage wire |
| WO1998036424A1 (en) * | 1997-02-14 | 1998-08-20 | Ifö Ceramics Aktiebolag | Electrical high-voltage insulator |
| EP1916672A1 (en) * | 2006-10-27 | 2008-04-30 | Borealis Technology Oy | Flexible power cable with improved water treeing resistance |
-
1986
- 1986-03-04 GB GB868605242A patent/GB8605242D0/en active Pending
-
1987
- 1987-03-02 GB GB8704814A patent/GB2187589B/en not_active Expired
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5460886A (en) * | 1988-12-16 | 1995-10-24 | Sumitomo Electric Industries, Ltd. | DC high-voltage wire |
| WO1998036424A1 (en) * | 1997-02-14 | 1998-08-20 | Ifö Ceramics Aktiebolag | Electrical high-voltage insulator |
| EP1916672A1 (en) * | 2006-10-27 | 2008-04-30 | Borealis Technology Oy | Flexible power cable with improved water treeing resistance |
| WO2008049636A1 (en) * | 2006-10-27 | 2008-05-02 | Borealis Technology Oy | Flexible power cable with improved water treeing resistance |
| US8269109B2 (en) | 2006-10-27 | 2012-09-18 | Borealis Technology Oy | Flexible power cable with improved water treeing resistance |
Also Published As
| Publication number | Publication date |
|---|---|
| GB8605242D0 (en) | 1986-04-09 |
| GB8704814D0 (en) | 1987-04-08 |
| GB2187589B (en) | 1989-11-22 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PCNP | Patent ceased through non-payment of renewal fee |