EP0539905B1 - Electrical cable - Google Patents
Electrical cable Download PDFInfo
- Publication number
- EP0539905B1 EP0539905B1 EP19920118276 EP92118276A EP0539905B1 EP 0539905 B1 EP0539905 B1 EP 0539905B1 EP 19920118276 EP19920118276 EP 19920118276 EP 92118276 A EP92118276 A EP 92118276A EP 0539905 B1 EP0539905 B1 EP 0539905B1
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- EP
- European Patent Office
- Prior art keywords
- phase
- cable according
- cable
- thermoplastic
- voltage
- 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
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- 229920002725 thermoplastic elastomer Polymers 0.000 claims description 9
- 239000011810 insulating material Substances 0.000 claims description 8
- 229910052751 metal Inorganic materials 0.000 claims description 8
- 239000002184 metal Substances 0.000 claims description 8
- -1 polyethylene Polymers 0.000 claims description 8
- 229920001169 thermoplastic Polymers 0.000 claims description 8
- 239000004416 thermosoftening plastic Substances 0.000 claims description 8
- PPBRXRYQALVLMV-UHFFFAOYSA-N Styrene Chemical compound C=CC1=CC=CC=C1 PPBRXRYQALVLMV-UHFFFAOYSA-N 0.000 claims description 6
- 229920001971 elastomer Polymers 0.000 claims description 6
- 239000004698 Polyethylene Substances 0.000 claims description 5
- 229920000573 polyethylene Polymers 0.000 claims description 5
- 229920001195 polyisoprene Polymers 0.000 claims description 5
- 230000001681 protective effect Effects 0.000 claims description 5
- 239000005062 Polybutadiene Substances 0.000 claims description 4
- 229920002857 polybutadiene Polymers 0.000 claims description 4
- 229920000181 Ethylene propylene rubber Polymers 0.000 claims description 3
- 239000004743 Polypropylene Substances 0.000 claims description 3
- 229920001155 polypropylene Polymers 0.000 claims description 3
- 239000000806 elastomer Substances 0.000 claims 4
- 150000001336 alkenes Chemical class 0.000 claims 1
- 230000005611 electricity Effects 0.000 claims 1
- JRZJOMJEPLMPRA-UHFFFAOYSA-N olefin Natural products CCCCCCCC=C JRZJOMJEPLMPRA-UHFFFAOYSA-N 0.000 claims 1
- 239000012071 phase Substances 0.000 description 24
- 239000000463 material Substances 0.000 description 13
- 239000004065 semiconductor Substances 0.000 description 10
- 238000009825 accumulation Methods 0.000 description 8
- 230000035508 accumulation Effects 0.000 description 8
- 230000015556 catabolic process Effects 0.000 description 6
- 230000005684 electric field Effects 0.000 description 6
- 229910052500 inorganic mineral Inorganic materials 0.000 description 6
- 239000011707 mineral Substances 0.000 description 6
- 239000002245 particle Substances 0.000 description 6
- 239000012212 insulator Substances 0.000 description 5
- 238000004519 manufacturing process Methods 0.000 description 5
- 230000015572 biosynthetic process Effects 0.000 description 4
- 229920003020 cross-linked polyethylene Polymers 0.000 description 4
- 239000004703 cross-linked polyethylene Substances 0.000 description 4
- 239000012535 impurity Substances 0.000 description 4
- 230000002787 reinforcement Effects 0.000 description 4
- 239000004793 Polystyrene Substances 0.000 description 3
- 239000006227 byproduct Substances 0.000 description 3
- 238000001125 extrusion Methods 0.000 description 3
- 238000009413 insulation Methods 0.000 description 3
- 229920002223 polystyrene Polymers 0.000 description 3
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 2
- RRHGJUQNOFWUDK-UHFFFAOYSA-N Isoprene Chemical compound CC(=C)C=C RRHGJUQNOFWUDK-UHFFFAOYSA-N 0.000 description 2
- 229910052782 aluminium Inorganic materials 0.000 description 2
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 2
- 229920001400 block copolymer Polymers 0.000 description 2
- 238000010382 chemical cross-linking Methods 0.000 description 2
- 238000004132 cross linking Methods 0.000 description 2
- 239000006185 dispersion Substances 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 230000009931 harmful effect Effects 0.000 description 2
- 150000001451 organic peroxides Chemical class 0.000 description 2
- 239000012074 organic phase Substances 0.000 description 2
- 239000005060 rubber Substances 0.000 description 2
- 229920002994 synthetic fiber Polymers 0.000 description 2
- 239000004411 aluminium Substances 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 229910052802 copper Inorganic materials 0.000 description 1
- 239000010949 copper Substances 0.000 description 1
- 238000000354 decomposition reaction Methods 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- 238000010494 dissociation reaction Methods 0.000 description 1
- 230000005593 dissociations Effects 0.000 description 1
- 238000005194 fractionation Methods 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
- 239000012774 insulation material Substances 0.000 description 1
- 238000004898 kneading Methods 0.000 description 1
- 230000007774 longterm Effects 0.000 description 1
- 229920001684 low density polyethylene Polymers 0.000 description 1
- 239000004702 low-density polyethylene Substances 0.000 description 1
- 239000011159 matrix material Substances 0.000 description 1
- 229920003023 plastic Polymers 0.000 description 1
- 239000004033 plastic Substances 0.000 description 1
- 230000010287 polarization Effects 0.000 description 1
- 238000012827 research and development Methods 0.000 description 1
- 238000003786 synthesis reaction Methods 0.000 description 1
- 239000012815 thermoplastic material Substances 0.000 description 1
Images
Classifications
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- 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
- H01B3/28—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances natural or synthetic rubbers
-
- 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 present invention relates to an electric cable intended to be used more particularly under high voltages (typically greater than 60 kV) in direct current.
- the object of the present invention is therefore to produce an electric cable in which the material constituting the insulating envelope makes it possible to reduce the phenomenon of accumulation of space charges in the presence of a high DC voltage.
- the thermoplastic rubber can be of olefinic type.
- the thermoplastic phase can be chosen from polyethylene and polypropylene, and the elastomeric phase consisting of an ethylene-propylene rubber.
- the thermoplastic rubber can be of styrenic type.
- the elastomeric phase optionally hydrogenated, can be chosen from polybutadiene and polyisoprene, and the thermoplastic phase consisting of polystyrene.
- a first semiconductor screen can be interposed between the conductive core and the envelope of an insulating material, and a second semiconductor screen can be interposed between the envelope of an insulating material and the metal screen.
- the insulating jacket can be extruded.
- the cable according to the invention can be used under high continuous voltages.
- the single figure shows in exploded perspective a cable for direct voltage, and in particular for high direct voltage, according to the invention.
- Thermoplastic rubbers consist of two mutually incompatible phases: a so-called thermoplastic phase (phase T), and a so-called elastomeric phase (phase E).
- phase T thermoplastic phase
- phase E elastomeric phase
- olefinic CTs and styrenic CTs olefinic CTs and styrenic CTs.
- the T phase can be prepared from polypropylene or high or low density polyethylene, and the E phase is generally constituted by an ethylene-propylene rubber.
- the proportion of polyethylene in the CT is in this case, preferably but not limited to, between 10 and 25%.
- a dynamic crosslinking of phase E is carried out in the presence of phase T, that is to say that phase E is crosslinked by strongly kneading the assembly, which allows the fractionation of phase E and its dispersion in the form of aggregates in phase T.
- phase T consists for example of a non-crystalline polystyrene, and phase E of non-crosslinked polybutadiene or polyisoprene .
- the polystyrene is grafted onto the polybutadiene for example, at the end of the latter chain and by grouping into "domains" of small dimensions (diameter of the order of 30 nm), while the matrix rubber (or phase E) remains continuous.
- the material is thus made up of a succession of rigid segments in a continuous rubber phase.
- CTs therefore generally have an organic phase dispersed in a continuous organic phase.
- This dispersion of aggregates creates numerous interfaces within the insulating envelope.
- any space charges no longer accumulate only at the interfaces between semiconductor screens and insulating envelope, but are also distributed at the numerous internal interfaces of the insulating envelope. Consequently, there are no longer any significant accumulations of space charges at the interfaces between semiconductor screens and insulating envelope, and the accumulations dispersed in the insulating envelope do not generate, under the effect of a continuous operating voltage, only weak reinforcements of the local electric field.
- CTs give better results than PRCs with regard to the accumulation of space charges. In addition, they are much simpler to implement. Indeed, with the PRC, chemical crosslinking takes place during the manufacture of the cable and immediately after the extrusion of the insulating jacket. It is carried out under pressure and at a very high temperature (of the order of 200 ° C); cooling is also carried out under pressure. The manufacturing process is therefore very cumbersome.
- the CTs are synthesized before manufacture, and their implementation is carried out by heating and extrusion around the cable as for any other thermoplastic material. They do not lose their thermoplastic character when heated for extrusion.
- High amplitude impulse withstand tests were also carried out.
- the resistance of the materials tested to pulses of high amplitude is determined either by direct application of a pulse of increasing voltage until the breakdown of the insulator, or by application of this pulse of increasing voltage after a prepolarization of one hour under a DC voltage equal to a third of the expected breakdown voltage.
- Vo the breakdown voltage without prepolarization
- Vp the breakdown voltage with prepolarization.
- the relationship between these two values gives an idea of the resistance to high amplitude pulses superimposed on a continuous operating voltage of the materials tested: for PRC, the ratio Vp Vo is 0.7; for TCs, the report Vp Vo is equal to 1.
- CTs are currently available on the market and are used as insulators in cables for low AC voltage.
- CTs have the particularity, because of their molecular constitution, of behaving both as plastic materials at the temperatures at which they are used for the manufacture of cables, and as rubbery materials at current temperatures of use . They are therefore used in the field of alternative low voltages for their ease of implementation and for their advantageous mechanical and thermal properties.
- thermoplastic rubbers although having a resistance to impulses of high amplitude less good than that of PRCs, show themselves to be much better than the latter when they are subjected to pulses. high amplitude superimposed on a continuous operating voltage, and can therefore be used as insulators for cables for high continuous voltage.
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- Physics & Mathematics (AREA)
- Spectroscopy & Molecular Physics (AREA)
- Organic Insulating Materials (AREA)
Description
La présente invention concerne un câble électrique destiné à être utilisé plus particulièrement sous de hautes tensions (typiquement supérieures à 60 kV) en courant continu.The present invention relates to an electric cable intended to be used more particularly under high voltages (typically greater than 60 kV) in direct current.
Les câbles de transport d'énergie sous haute tension en courant continu sont de plus en plus utilisés actuellement car ils ont un rendement bien meilleur que celui des câbles haute tension alternative. Ces câbles sont généralement constitués d'une âme conductrice entourée :
- éventuellement d'un premier écran semi-conducteur,
- d'une enveloppe isolante,
- éventuellement d'un second écran semi-conducteur,
- d'un écran métallique,
- d'une gaine extérieure de protection en un matériau synthétique.
- possibly a first semiconductor screen,
- an insulating jacket,
- possibly a second semiconductor screen,
- a metal screen,
- an outer protective sheath made of synthetic material.
En ce qui concerne l'enveloppe isolante, plusieurs matériaux sont envisageables pour sa réalisation.With regard to the insulating envelope, several materials can be envisaged for its production.
En premier lieu, on pourrait penser à utiliser un matériau employé pour les câbles à haute tension alternative, c'est-à-dire par exemple le polyéthylène réticulé chimiquement (noté PRC dans la suite), qui présente de très bonnes propriétés thermiques, mécaniques et électriques. La réticulation chimique du polyéthylène est obtenue par addition à ce dernier de peroxydes organiques qui se dissocient à température élevée pour former des radicaux libres venant réticuler entre elles les chaînes linéaires de polyéthylène. La décomposition ou dissociation de ces peroxydes organiques conduit également à la formation de sous-produits. Ces sous-produits se sont avérés d'un effet néfaste en courant continu. En effet, sous l'action d'une tension de service continue, ces sous-produits sont à l'origine de la formation de charges importantes qui migrent à proximité des interfaces entre les écrans semi-conducteurs et l'enveloppe isolante (ou bien entre l'enveloppe isolante et l'âme conductrice d'une part et entre l'enveloppe isolante et l'écran métallique d'autre part, lorsque le câble ne comporte pas d'écrans semi-conducteurs) où elles sont la cause de renforcements locaux du champ électrique. L'intensité du champ électrique peut ainsi atteindre au voisinage des interfaces deux à trois fois l'intensité du champ électrique nominal, de sorte que la tension de claquage de l'enveloppe isolante peut être rapidement atteinte, notamment lorsqu'une impulsion de forte amplitude (due à la foudre par exemple) se superpose à la tension de service continue. On observe alors à terme une perforation de cette enveloppe isolante et par conséquent une détérioration du câble. L'utilisation du PRC comme isolant de câbles pour haute tension continue n'est donc pas souhaitable.First, one could think of using a material used for high-voltage alternating cables, that is to say for example chemically crosslinked polyethylene (noted PRC below), which has very good thermal and mechanical properties. and electric. The chemical crosslinking of the polyethylene is obtained by adding to the latter organic peroxides which dissociate at high temperature to form free radicals which crosslink the linear chains of polyethylene. The decomposition or dissociation of these organic peroxides also leads to the formation of by-products. These by-products have been shown to have a harmful effect on direct current. Indeed, under the action of a continuous operating voltage, these by-products are at the origin of the formation of large charges which migrate near the interfaces between the semiconductor screens and the insulating envelope (or else between the insulating jacket and the conductive core on the one hand and between the insulating envelope and the metal screen on the other hand, when the cable does not include semiconductor screens) where they are the cause of local reinforcements of the electric field. The intensity of the electric field can thus reach in the vicinity of the interfaces two to three times the intensity of the nominal electric field, so that the breakdown voltage of the insulating envelope can be quickly reached, in particular when a pulse of high amplitude (due to lightning, for example) is superimposed on the continuous operating voltage. In the long term, there is then a perforation of this insulating envelope and therefore deterioration of the cable. The use of PRC as cable insulator for high direct voltage is therefore not desirable.
On pourrait alors penser à utiliser du polyéthylène réticulé par irradiation. L'épaisseur de l'enveloppe isolante nécessaire pour les applications en haute tension et en courant continu (de l'ordre de 2 cm) rend la réticulation par irradiation difficile et en pratique de mauvaise qualité.One could then think of using crosslinked polyethylene by irradiation. The thickness of the insulating jacket necessary for high voltage and direct current applications (of the order of 2 cm) makes crosslinking by irradiation difficult and in practice of poor quality.
Un autre type de matériaux a récemment été proposé pour l'isolation des câbles pour haute tension continue. Ce sont des matériaux à base de PRC contenant des particules minérales, et dont les performances sont décrites par exemple dans un article intitulé "Research and development of DC XLPE cables" paru dans JI CABLE 87. Ces matériaux permettraient d'éviter le phénomène néfaste de l'accumulation des charges d'espace aux interfaces. Toutefois, pour parvenir à ce résultat, il est nécessaire, comme cela est précisé dans l'article mentionné ci-dessus, que la pureté des particules minérales introduites dans le PRC soit minutieusement contrôlée afin d'éviter l'introduction simultanée d'impuretés diverses dans le PRC. En effet, la présence d'une très petite quantité d'impuretés suffit à provoquer l'accumulation de charges d'espace, car les impuretés peuvent se dissocier sous l'action du champ électrique pour former des charges d'espace. Or il est en pratique difficile et fastidieux d'introduire des particules minérales très purifiées dans le PRC. L'utilisation de PRC contenant des particules minérales est donc peu envisageable.Another type of material has recently been proposed for the insulation of cables for high direct voltage. These are PRC-based materials containing mineral particles, the performance of which is described for example in an article entitled "Research and development of DC XLPE cables" published in JI CABLE 87. These materials would avoid the harmful phenomenon of the accumulation of space charges at the interfaces. However, to achieve this result, it is necessary, as specified in the article mentioned above, that the purity of the mineral particles introduced into the PRC is carefully controlled in order to avoid the simultaneous introduction of various impurities in the PRC. Indeed, the presence of a very small amount of impurities is sufficient to cause the accumulation of space charges, because impurities can dissociate under the action of the electric field to form space charges. However, it is in practice difficult and tedious to introduce highly purified mineral particles into the PRC. The use of PRCs containing mineral particles is therefore hardly conceivable.
Le but de la présente invention est donc de réaliser un câble électrique dans lequel le matériau constituant l'enveloppe isolante permet de réduire le phénomène d'accumulation de charges d'espace en présence d'une haute tension continue.The object of the present invention is therefore to produce an electric cable in which the material constituting the insulating envelope makes it possible to reduce the phenomenon of accumulation of space charges in the presence of a high DC voltage.
La présente invention propose à cet effet un câble électrique comprenant, disposés coaxialement de l'intérieur vers l'extérieur :
- une âme conductrice,
- une enveloppe en un matériau isolant,
- un écran métallique,
- une gaine extérieure de protection,
- a conductive soul,
- an envelope of insulating material,
- a metal screen,
- an outer protective sheath,
Grâce à l'utilisation d'un tel isolant, l'accumulation des charges d'espace aux interfaces entre l'enveloppe isolante et l'âme conductrice d'une part, et entre l'enveloppe isolante et l'écran métallique d'autre part, en présence d'une haute tension continue, est réduite par rapport aux câbles de l'art antérieur.Thanks to the use of such an insulator, the accumulation of space charges at the interfaces between the insulating envelope and the conductive core on the one hand, and between the insulating envelope and the metal screen on the other part, in the presence of a high DC voltage, is reduced compared to the cables of the prior art.
Selon une première possibilité, le caoutchouc thermoplastique peut être de type oléfinique. Dans ce cas, la phase thermoplastique peut être choisie parmi le polyéthylène et le polypropylène, et la phase élastomérique constituée d'un caoutchouc d'éthylène-propylène.According to a first possibility, the thermoplastic rubber can be of olefinic type. In this case, the thermoplastic phase can be chosen from polyethylene and polypropylene, and the elastomeric phase consisting of an ethylene-propylene rubber.
Selon une deuxième possibilité, le caoutchouc thermoplastique peut être de type styrénique. Dans ce cas, la phase élastomérique, éventuellement hydrogénée, peut être choisie parmi le polybutadiène et le polyisoprène, et la phase thermoplastique constituée de polystyrène.According to a second possibility, the thermoplastic rubber can be of styrenic type. In this case, the elastomeric phase, optionally hydrogenated, can be chosen from polybutadiene and polyisoprene, and the thermoplastic phase consisting of polystyrene.
Enfin, un premier écran semi-conducteur peut être interposé entre l'âme conductrice et l'enveloppe en un matériau isolant, et un deuxième écran semi-conducteur peut être interposé entre l'enveloppe en un matériau isolant et l'écran métallique.Finally, a first semiconductor screen can be interposed between the conductive core and the envelope of an insulating material, and a second semiconductor screen can be interposed between the envelope of an insulating material and the metal screen.
L'enveloppe isolante peut être extrudée.The insulating jacket can be extruded.
Le câble selon l'invention peut être utilisé sous de hautes tensions continues.The cable according to the invention can be used under high continuous voltages.
D'autres caractéristiques et avantages de la présente invention apparaîtront dans la description suivante d'un câble selon l'invention, donnée à titre illustratif et nullement limitatif.Other characteristics and advantages of the present invention will appear in the following description of a cable according to the invention, given by way of illustration and in no way limitative.
La figure unique représente en perspective éclatée un câble pour tension continue, et en particulier pour haute tension continue, selon l'invention.The single figure shows in exploded perspective a cable for direct voltage, and in particular for high direct voltage, according to the invention.
Dans cette figure, un câble 1 pour haute tension continue comprend :
- une âme conductrice 2 en cuivre ou en aluminium,
- un premier écran semi-conducteur 3,
- une enveloppe isolante 4 constituée, selon l'invention, d'un caoutchouc thermoplastique,
- un second écran semi-conducteur 5,
- un écran métallique de
protection 6, - une gaine extérieure de
protection 7 en un matériau synthétique.
- a
conductive core 2 of copper or aluminum, - a first semiconductor screen 3,
- an insulating envelope 4 made up, according to the invention, of a thermoplastic rubber,
- a second semiconductor screen 5,
- a
protective metal screen 6, - an outer
protective sheath 7 made of a synthetic material.
Les caoutchoucs thermoplastiques (CT) sont constitués de deux phases incompatibles entre elles : une phase dite thermoplastique (phase T), et une phase dite élastomérique (phase E). On donne ci-après l'exemple, non limitatif, de deux familles de CT possibles pour l'application de l'invention : les CT oléfiniques et les CT styréniques.Thermoplastic rubbers (CT) consist of two mutually incompatible phases: a so-called thermoplastic phase (phase T), and a so-called elastomeric phase (phase E). The following is a non-limiting example of two families of possible CTs for the application of the invention: olefinic CTs and styrenic CTs.
Dans les CT oléfiniques, la phase T peut être préparée à partir de polypropylène ou de polyéthylène haute ou basse densité, et la phase E est généralement constituée par un caoutchouc d'éthylène-propylène. La proportion de polyéthylène dans le CT est comprise dans ce cas, de préférence mais de manière non limitative, entre 10 et 25%. Afin d'obtenir le CT ayant la structure souhaitée, on procède à une réticulation dynamique de la phase E en présence de la phase T, c'est-à-dire que l'on réticule la phase E en malaxant fortement l'ensemble, ce qui permet le fractionnement de la phase E et sa dispersion sous forme d'agrégats dans la phase T.In olefinic CTs, the T phase can be prepared from polypropylene or high or low density polyethylene, and the E phase is generally constituted by an ethylene-propylene rubber. The proportion of polyethylene in the CT is in this case, preferably but not limited to, between 10 and 25%. In order to obtain the CT having the desired structure, a dynamic crosslinking of phase E is carried out in the presence of phase T, that is to say that phase E is crosslinked by strongly kneading the assembly, which allows the fractionation of phase E and its dispersion in the form of aggregates in phase T.
Dans les CT styréniques, c'est-à-dire dans les copolymères séquencés à base de styrène, ou copolymères blocs, la phase T est constituée par exemple d'un polystyrène non cristallin, et la phase E de polybutadiène ou de polyisoprène non réticulé. Lors de la synthèse du CT, le polystyrène se greffe sur le polybutadiène par exemple, en bout de chaîne de ce dernier et en se regroupant en "domaines" de faibles dimensions (diamètre de l'ordre de 30 nm), tandis que la matrice caoutchoutique (ou phase E) reste continue. Le matériau est ainsi constitué d'une succession de segments rigides dans une phase caoutchoutique continue.In styrenic CTs, that is to say in block copolymers based on styrene, or block copolymers, phase T consists for example of a non-crystalline polystyrene, and phase E of non-crosslinked polybutadiene or polyisoprene . During the synthesis of the CT, the polystyrene is grafted onto the polybutadiene for example, at the end of the latter chain and by grouping into "domains" of small dimensions (diameter of the order of 30 nm), while the matrix rubber (or phase E) remains continuous. The material is thus made up of a succession of rigid segments in a continuous rubber phase.
Les CT présentent donc de manière générale une phase organique dispersée dans une phase organique continue. Cette dispersion d'agrégats crée de nombreux interfaces au sein même de l'enveloppe isolante. De ce fait, les charges d'espace éventuelles ne s'accumulent plus seulement aux interfaces entre écrans semi-conducteurs et enveloppe isolante, mais se répartissent également au niveau des nombreux interfaces internes de l'enveloppe isolante. Dès lors, on ne trouve plus d'accumulations importantes de charges d'espace aux interfaces entre écrans semi-conducteurs et enveloppe isolante, et les accumulations dispersées dans l'enveloppe isolante ne génèrent, sous l'effet d'une tension de service continue, que de faibles renforcements du champ électrique local.CTs therefore generally have an organic phase dispersed in a continuous organic phase. This dispersion of aggregates creates numerous interfaces within the insulating envelope. As a result, any space charges no longer accumulate only at the interfaces between semiconductor screens and insulating envelope, but are also distributed at the numerous internal interfaces of the insulating envelope. Consequently, there are no longer any significant accumulations of space charges at the interfaces between semiconductor screens and insulating envelope, and the accumulations dispersed in the insulating envelope do not generate, under the effect of a continuous operating voltage, only weak reinforcements of the local electric field.
L'isolation des câbles pour haute tension continue au moyen de CT permet de résoudre tous les problèmes posés par les divers matériaux de l'art antérieur envisageables.The insulation of cables for continuous high voltage by means of CT makes it possible to solve all the problems posed by the various possible prior art materials.
Comme cela vient d'être décrit, les CT donnent de meilleurs résultats que les PRC en ce qui concerne l'accumulation de charges d'espace. De plus, ils sont d'une mise en oeuvre beaucoup plus simple. En effet, avec le PRC, la réticulation chimique a lieu pendant la fabrication du câble et immédiatement après l'extrusion de l'enveloppe isolante. Elle est effectuée sous pression et à une température très élevée (de l'ordre de 200°C) ; le refroidissement est également effectué sous pression. Le processus de fabrication est donc très lourd. En revanche, les CT sont synthétisés avant la fabrication, et leur mise en oeuvre se fait par chauffage et extrusion autour du câble comme pour tout autre matériau thermoplastique. Ils ne perdent pas leur caractère thermoplastique lors du chauffage en vue de l'extrusion.As has just been described, CTs give better results than PRCs with regard to the accumulation of space charges. In addition, they are much simpler to implement. Indeed, with the PRC, chemical crosslinking takes place during the manufacture of the cable and immediately after the extrusion of the insulating jacket. It is carried out under pressure and at a very high temperature (of the order of 200 ° C); cooling is also carried out under pressure. The manufacturing process is therefore very cumbersome. On the other hand, the CTs are synthesized before manufacture, and their implementation is carried out by heating and extrusion around the cable as for any other thermoplastic material. They do not lose their thermoplastic character when heated for extrusion.
Par ailleurs, la formation d'agrégats organiques étant une caractéristique intrinsèque des CT, les risques de présence d'impuretés extérieures sont faibles par rapport au cas de l'introduction de particules minérales dans du PRC. De plus, la mise en oeuvre des CT est plus simple que celle d'un PRC à particules minérales.Furthermore, the formation of organic aggregates being an intrinsic characteristic of CTs, the risks of presence of external impurities are low compared to the case of the introduction of mineral particles in PRC. In addition, the implementation of CTs is simpler than that of a PRC with mineral particles.
Des tests effectués en laboratoire montrent que, dans les mêmes conditions d'expérimentation, les PRC et les CT ont un comportement totalement différent. Ainsi, les renforcements locaux de champ électrique dus à l'accumulation de charges d'espace sont beaucoup plus faibles pour les CT : après une heure de polarisation continue à 20°C, le renforcement de champ au voisinage des interfaces est de l'ordre de 110% par rapport à la valeur du champ appliqué pour les PRC, alors qu'il est inférieur à 20% pour les CT.Tests carried out in the laboratory show that, under the same experimental conditions, the PRCs and the CTs have a completely different behavior. Thus, the local electric field reinforcements due to the accumulation of space charges are much weaker for the CTs: after one hour of continuous polarization at 20 ° C, the field reinforcement in the vicinity of the interfaces is of the order 110% compared to the value of the field applied for PRC, while it is less than 20% for CT.
Des tests de tenue aux impulsions de forte amplitude ont également été effectués. La tenue des matériaux testés à des impulsions de forte amplitude est déterminée soit par application directe d'une impulsion de tension croissante jusqu'au claquage de l'isolant, soit par application de cette impulsion de tension croissante après une prépolarisation d'une heure sous une tension continue égale au tiers de la tension de claquage espérée. On appelle Vo la tension de claquage sans prépolarisation, et Vp la tension de claquage avec prépolarisation. Le rapport entre ces deux valeurs donne une idée de la tenue aux impulsions de forte amplitude superposées à une tension de service continue des matériaux testés : pour les PRC, le rapport
Les CT sont disponibles actuellement sur le marché et sont utilisés comme isolants dans les câbles pour basse tension alternative. Les CT présentent en effet la particularité, du fait de leur constitution moléculaire, de se comporter à la fois comme des matériaux plastiques aux températures auxquelles ils sont mis en oeuvre pour la fabrication des câbles, et comme des matériaux caoutchoutiques aux températures courantes d'utilisation. Ils sont donc utilisés dans le domaine des basses tensions alternatives pour leur facilité de mise en oeuvre et pour leurs propriétés mécaniques et thermiques intéressantes.CTs are currently available on the market and are used as insulators in cables for low AC voltage. CTs have the particularity, because of their molecular constitution, of behaving both as plastic materials at the temperatures at which they are used for the manufacture of cables, and as rubbery materials at current temperatures of use . They are therefore used in the field of alternative low voltages for their ease of implementation and for their advantageous mechanical and thermal properties.
Il est bien connu par ailleurs que la tenue aux impulsions de forte amplitude d'un matériau augmente avec son taux de cristallinité. L'article intitulé "The effect of morphology on the impulse breakdown in XLPE cable insulation" paru dans IEEE Vol. EI17 n°5 d'Octobre 1982, en page 386, montre à cet égard une courbe donnant la tenue aux impulsions de forte amplitude en fonction du taux de cristallinité. Or les CT sont très peu cristallins, et ont donc une tenue aux impulsions de forte amplitude médiocre. C'est pourquoi ils n'ont pas été envisagés jusqu'à présent comme matériaux d'isolation de câbles pour haute tension continue.It is also well known that the resistance to high amplitude pulses of a material increases with its rate of crystallinity. The article entitled "The effect of morphology on the impulse breakdown in XLPE cable insulation" published in IEEE Vol. EI17 n ° 5 of October 1982, on page 386, shows in this respect a curve giving the resistance to high amplitude pulses as a function of the crystallinity rate. However, the CTs are not very crystalline, and therefore have a resistance to impulses of high mediocre amplitude. This is why they have not been considered so far. as cable insulation materials for high continuous voltage.
Contrairement à ce qui était communément admis, on a donc découvert que les caoutchoucs thermoplastiques, bien qu'ayant une tenue aux impulsions de forte amplitude moins bonne que celle des PRC, se montrent bien meilleurs que ces derniers lorsqu'ils sont soumis à des impulsions de forte amplitude superposées à une tension de service continue, et peuvent en conséquence être utilisés comme isolants pour des câbles pour haute tension continue.Contrary to what was commonly accepted, it has therefore been discovered that thermoplastic rubbers, although having a resistance to impulses of high amplitude less good than that of PRCs, show themselves to be much better than the latter when they are subjected to pulses. high amplitude superimposed on a continuous operating voltage, and can therefore be used as insulators for cables for high continuous voltage.
Bien évidemment, l'invention n'est pas limitée au mode de réalisation qui vient d'être décrit : les valeurs numériques fournies ne le sont qu'à titre indicatif, et l'on pourra remplacer tout moyen par un moyen équivalent sans sortir du cadre de l'invention.Obviously, the invention is not limited to the embodiment which has just been described: the numerical values supplied are only for information only, and any means can be replaced by equivalent means without departing from the part of the invention.
Claims (11)
- An electricity cable comprising the following disposed coaxially going from the inside to the outside:a conductive core (2);a covering made of an insulating material (4);a metal screen (6); anda protective outer sheath (7);said cable being characterized in that said insulating material is constituted by a thermoplastic rubber comprising an elastomer phase and a thermoplastic phase.
- A cable according to claim 1, characterized in that said thermoplastic rubber is of the olefin type.
- A cable according to claim 2, characterized in that said thermoplastic phase is chosen from polyethylene and polypropylene.
- A cable according to claim 2 or 3, characterized in that said elastomer phase is constituted by an ethylene-propylene rubber.
- A cable according to claim 1, characterized in that said thermoplastic rubber of the styrene type.
- A cable according to claim 5, characterized in that said elastomer phase is hydrogenated.
- A cable according to claim 5 or 6, characterized in that said elastomer phase is chosen from polybutadiene and polyisoprene.
- A cable according to any one of claims 5 to 7, characterized in that said thermoplastic phase is constituted by styrene.
- A cable according to any one of claims 1 to 8, characterized in that a first semiconductive screen (3) is interposed between said conductive core (2) and said covering made of an insulating material (4), and in that a second semiconductive screen (5) is interposed between said covering made of an insulating material (4) and said metal screen (6).
- A cable according to any one of claims 1 to 9, characterized in that said covering is extruded.
- A cable according to any one of claims 1 to 10, characterized in that it is used for high tension DC.
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
FR9113511 | 1991-10-31 | ||
FR9113511A FR2683378B1 (en) | 1991-10-31 | 1991-10-31 | ELECTRIC CABLE. |
Publications (2)
Publication Number | Publication Date |
---|---|
EP0539905A1 EP0539905A1 (en) | 1993-05-05 |
EP0539905B1 true EP0539905B1 (en) | 1997-08-27 |
Family
ID=9418542
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP19920118276 Expired - Lifetime EP0539905B1 (en) | 1991-10-31 | 1992-10-26 | Electrical cable |
Country Status (3)
Country | Link |
---|---|
EP (1) | EP0539905B1 (en) |
DE (1) | DE69221814T2 (en) |
FR (1) | FR2683378B1 (en) |
Families Citing this family (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
FR2714543B1 (en) * | 1993-12-23 | 1996-01-19 | Euromold | Device for joining power cables. |
WO2013030206A1 (en) * | 2011-08-30 | 2013-03-07 | Borealis Ag | Power cable comprising polypropylene |
Family Cites Families (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3569610A (en) * | 1969-10-15 | 1971-03-09 | Gen Cable Corp | Ethylene-propylene rubber insulated cable with cross-linked polyethylene strand shielding |
CA947388A (en) * | 1971-05-24 | 1974-05-14 | Gordon C. Gainer | Solid insulation for electrical apparatus |
JPS6111854Y2 (en) * | 1980-01-31 | 1986-04-14 | ||
JPS60235304A (en) * | 1984-05-08 | 1985-11-22 | 株式会社フジクラ | Dc power cable |
EP0712139A3 (en) * | 1990-01-31 | 1998-03-25 | Fujikura Ltd. | Electric insulated wire and cable using the same |
-
1991
- 1991-10-31 FR FR9113511A patent/FR2683378B1/en not_active Expired - Fee Related
-
1992
- 1992-10-26 EP EP19920118276 patent/EP0539905B1/en not_active Expired - Lifetime
- 1992-10-26 DE DE1992621814 patent/DE69221814T2/en not_active Expired - Fee Related
Also Published As
Publication number | Publication date |
---|---|
DE69221814T2 (en) | 1998-01-02 |
EP0539905A1 (en) | 1993-05-05 |
FR2683378B1 (en) | 1993-12-31 |
FR2683378A1 (en) | 1993-05-07 |
DE69221814D1 (en) | 1997-10-02 |
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