Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
  • H01B7/00—Insulated conductors or cables characterised by their form
  • H01B7/17—Protection against damage caused by external factors, e.g. sheaths or armouring
  • H01B7/29—Protection against damage caused by extremes of temperature or by flame
  • H01B7/295—Protection against damage caused by extremes of temperature or by flame using material resistant to flame
• • 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
• • 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
  • H01B3/447—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 acrylic compounds
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
  • H01B7/00—Insulated conductors or cables characterised by their form
  • H01B7/02—Disposition of insulation
  • H01B7/0208—Cables with several layers of insulating material
  • H01B7/0225—Three or more layers
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
  • H01B9/00—Power cables

Definitions

• Electrical cable capable of ensuring the continuity of electrical distribution in case of fire
• the present invention relates to an electrical cable adapted to ensure the continuity of electrical distribution in case of fire comprising one or more insulated electrical conductors.
• safety cables are in particular power transmission cables or low frequency transmission cables, such as control or signaling cables.
• the cable In case of fire, the cable must be able to withstand the fire in order to operate as long as possible and limit its degradation.
• a safety cable must also not be dangerous for its environment, that is to say not to spread the fire and not to release toxic fumes and / or opaque when subjected to extreme thermal conditions.
• a halogen-free and fire-resistant electrical safety cable comprising a set of insulated electrical conductors, said assembly being surrounded by a outer sheath.
• Each insulated electrical conductor is formed by an electrical conductor surrounded by a polymeric insulating monolayer obtained from a composition comprising a polymeric material and at least one ceramic-forming filler, said polymeric insulating layer thus being able to convert at least superficially into the ceramic state at high temperatures corresponding to fire conditions.
• the polymeric material of this single insulating layer is selected from a polysiloxane (polyorganosiloxane) and a copolymer of ethylene, or a mixture thereof.
• the purpose of the present invention is to overcome the drawbacks of the techniques of the prior art by proposing in particular an easily manipulated electric cable, limiting the risk of degradation mechanically insulated electrical conductors that compose it, while maintaining excellent fire resistance properties meeting the IEC 60331-21 standard and an improved electrical resistance meeting the IEC 60502-1 standard.
• the present invention relates to an electrical cable comprising one or more insulated electrical conductors, each of said insulated electrical conductors comprising an electrical conductor surrounded by an insulating layer, preferably an electrically insulating layer, the insulating layer comprising a first polymeric layer (2a) surrounding the electrical conductor, the first layer (2a) being obtained from a first composition comprising a polymer matrix based on thermoplastic polymer, and at least one ceramic forming filler, characterized in that the insulating layer further comprises a second crosslinked polymeric layer (2b) surrounding said first layer, the second layer (2b) being obtained from a second composition comprising a polyolefin-based polymer matrix and comprising substantially no ceramic forming filler or halogenated compound .
• first composition comprising a polymer matrix based on thermoplastic polymer
• second composition comprising a polyolefin-based polymer matrix
• the polymer (s) used in the second composition are predominantly one or more polyolefins (in% by weight in the matrix).
• halogenated compounds furthermore means a compound of all kinds comprising at least one halogen element, such as, for example, fluorinated polymers or chlorinated polymers such as polyvinyl chloride (PVC), halogenated plasticizers, halogenated mineral fillers, ... etc.
• halogenated compounds furthermore means a compound of all kinds comprising at least one halogen element, such as, for example, fluorinated polymers or chlorinated polymers such as polyvinyl chloride (PVC), halogenated plasticizers, halogenated mineral fillers, ... etc.
• outer layer based on polyolefin mechanically protects the first polymeric layer (inner layer) based on thermoplastic polymer.
• This property allows the insulating layer of each isolated electrical conductor to improve the mechanical properties of the cable, including the hardness, resistance to abrasion and tearing of the insulated electrical conductors that compose it, to facilitate the installation of said cable , and make the cable more robust during its manufacture, while ensuring a very good adhesion between the first layer and the second layer of the insulating layer.
• the insulating layer of the electric cable of the invention has excellent mechanical strength in temperature (or hot creep) meeting the EN 60811-2-1 standard.
• the electrical cable comprising the insulating layer according to the invention meets the IEC 60331-21 standard with excellent fire resistance properties.
• the electrical conductors are thus protected against fire, or in other words, the electric cable ensures a fire behavior of high quality in terms of at least cohesion electrically insulating ash.
• Another advantage of the insulating layer of the electric cable of the invention relates to its electrical resistance. Due to the absence of ceramic forming charge in the outer layer of the insulating layer of the invention, the electrical resistance properties of the cable to high temperature according to IEC 60502-1 are significantly improved.
• Another advantage of the insulating layer of the electrical cable of the invention is that it significantly limits the release of toxic fumes when subjected to extreme thermal conditions.
• the invention as thus defined finally has the advantage of being economical since it makes it possible to significantly limit, or even completely avoid, the use of polyorganosiloxane in the insulating layer of the isolated electrical conductors, while having very low good fire resistance properties.
• the first layer polvméri ⁇ ue crazy inner layer
• thermoplastic polymer of the first composition may be advantageously chosen from olefin polymers, acrylate or methacrylate polymers, vinyl polymers such as, for example, polyvinyl chloride, and fluoropolymers, or one of their mixtures.
• the olefin polymers are chosen from homopolymers of ethylene; copolymers of ethylene and octene (PEO); copolymers of ethylene and vinyl acetate (EVA); copolymers of ethylene and butyl acrylate (EBA); copolymers of ethylene and methyl acrylate (EMA); copolymers of ethylene and ethyl acrylate (EEA); copolymers of ethylene and butyl acrylate (EBA); copolymers of ethylene and ethyl acrylate (EEA); copolymers of ethylene, propylene and rubber (EPR); copolymers of ethyl propylene diene monomer (EPDM); or a mixture thereof.
• the polymer matrix of the first composition comprises at least 95% by weight of thermoplastic polymer, preferably said polymer matrix comprises only one or more thermoplastic polymers.
• the first composition does not comprise more than 5% by weight of polyorganosiloxane, preferably not more than 2% by weight of polyorganosiloxane, and even more preferably the first composition does not comprise polyorganosiloxane.
• the ceramic forming filler used in the first composition allows the first layer to convert at least superficially in the ceramic state at high temperatures corresponding to fire conditions, and thus form a first so-called "ceramizing" layer. This ceramizing layer thus provides sufficient insulation when the second layer (outer layer) has disappeared due to combustion phenomena.
• the ceramic forming filler according to the invention may be chosen from a fusible ceramic filler and a refractory filler, or a mixture thereof.
• the ceramic forming filler preferably comprises at least one fusible ceramic filler and at least one refractory filler.
• the fusible ceramic filler has a melting temperature lower than an elevated temperature T, and the refractory filler has a melting temperature greater than said temperature T.
• This temperature T is advantageously at least 75 ° C., and can reach HOO 0 C.
• the fusible ceramic filler may be at least one mineral filler selected from boron oxides (eg B 2 O 3 ), anhydrous zinc borates (eg 2ZnO 3B 2 O 3 ) or hydrated borates (eg 4ZnO B 2 O 3 H 2 O or 2ZnO 3B 2 O 3 3.5H 2 O), anhydrous boron phosphates (eg BPO 4 ) or hydrated, or one of their precursors.
• boron oxides eg B 2 O 3
• anhydrous zinc borates eg 2ZnO 3B 2 O 3
• hydrated borates eg 4ZnO B 2 O 3 H 2 O or 2ZnO 3B 2 O 3 3.5H 2 O
• anhydrous boron phosphates eg BPO 4
• calcium borosilicates may be mentioned as boron oxide precursor.
• This fusible ceramic charge typically has a melting point below 500 ° C. and gives rise to an amorphous phase (eg a glass) when the temperature exceeds 500 ° C.
• the refractory filler may be at least one mineral filler selected from magnesium oxides (eg MgO), calcium oxides (eg CaO), silicon oxides (eg SiO 2 or quartz), aluminum oxides (eg Al 2 O 3 ), chromium oxides (eg Cr 2 O 3 ), zirconium oxides (eg ZrO 2 ) and phyllosilicates such as, for example, montmorillonites, sepiolites, illites, attapulgites, talcs, kaolins or micas (eg muscovite mica 6 SiO 2 - 3 Al 2 O 3 - K 2 O - 2H 2 O), or a mixture thereof.
• magnesium oxides eg MgO
• CaO calcium oxides
• silicon oxides eg SiO 2 or quartz
• aluminum oxides eg Al 2 O 3
• chromium oxides eg Cr 2 O 3
• zirconium oxides eg ZrO 2
• the ceramic forming filler consists of two refractory fillers such as, for example, muscovite mica and calcium oxide CaO or one of its precursors (eg calcium carbonate CaCO 3 ), and a fusible ceramic filler. such as, for example, a boron oxide precursor.
• two refractory fillers such as, for example, muscovite mica and calcium oxide CaO or one of its precursors (eg calcium carbonate CaCO 3 ), and a fusible ceramic filler.
• a fusible ceramic filler such as, for example, a boron oxide precursor.
• the amount of ceramic-forming fillers can be defined in that the first composition comprises at least 90 parts by weight of said fillers per 100 parts by weight of polymer, preferably at most 250 parts by weight of said fillers per 100 parts by weight of polymers in order to limit the problems of rheologies in the composition. More particularly, the amount of fusible ceramic filler can range from 5 to 100 parts by weight, preferably from 20 to 80, and the amount of refractory filler can range from 50 to 200 parts by weight, preferably from 70 to 120 parts by weight. weight per 100 parts by weight of polymers in the first composition. In a preferred embodiment, the first composition is not crosslinked, or in other words the first layer formed around the electrical conductor is uncrosslinked.
• the first polymeric layer does not comprise halogenated compound.
• the second crosslinked polymeric layer is distinct from the first polymeric layer because it is said to be "non-ceramizing" since it does not substantially comprise any ceramic-forming filler.
• substantially means that the second composition may further comprise a ceramic forming filler but as an additive.
• the second layer can not have the properties of being converted at least superficially into the ceramic state at high temperatures corresponding to fire conditions, for example, for example when the second composition comprises less than 50 parts by weight. ceramic forming charge.
• the polyolefin of the second composition may be advantageously chosen from homopolymers and copolymers of ethylene, or a mixture thereof.
• LDPE low density polyethylene
• the copolymers of ethylene can be advantageously chosen from copolymers of ethylene and octene (PEO); copolymers of ethylene and vinyl acetate (EVA); the copolymers of ethylene and butyl acrylate (EBA); copolymers of ethylene and methyl acrylate (EMA); copolymers of ethylene and ethyl acrylate (EEA); copolymers of ethylene, propylene and rubber (EPR); and copolymers of ethylene propylene diene monomer (EPDM); or a mixture thereof.
• Copolymers of ethylene and vinyl acetate (EVA) as the preferred ethylene copolymer may be mentioned.
• the polymer matrix of the second composition is distinct from the polymer matrix of the first composition.
• the polymer matrix of the second composition comprises at least 95% by weight of polyolefin, preferably said polymer matrix comprises only one or more polyolefins.
• the second composition does not comprise more than 5% by weight of polyorganosiloxane, preferably not more than 2% by weight of polyorganosiloxane, and even more preferably the second composition does not comprise polyorganosiloxane.
• the second composition may further comprise at least one mineral filler different from a ceramic forming filler.
• the inorganic filler may be a hydrated flame retardant mineral filler, chosen in particular from metal hydroxides such as, for example, magnesium dihydroxide (MDH) or aluminum trihydroxide (ATH).
• MDH magnesium dihydroxide
• ATH aluminum trihydroxide
• the mineral filler may also be a carbonate, such as calcium carbonate.
• the amount of mineral fillers can be defined in that the second composition comprises at least 90 parts by weight of said fillers per 100 parts by weight of polymer, preferably at most 200 parts by weight of said fillers per 100 parts by weight of polymers in order to to limit the problems of rheologies in the composition.
• the second crosslinked polymeric layer of this first variant is particularly advantageous when associated with a first non-crosslinked polymeric layer comprising, as a ceramic-forming filler, only one or more refractory filler (s).
• the second layer is said to be "uncharged", or in other words the second layer, in addition to not including a ceramic-forming filler, does not comprise a hydrated flame retardant mineral filler, and more particularly not mineral charge.
• Crosslinking of the second composition to obtain the second crosslinked layer can be carried out by conventional crosslinking techniques well known to those skilled in the art such as, for example, silane crosslinking in the presence of a crosslinking agent, peroxide crosslinking under the action of heat, or photochemically crosslinking such as irradiation under beta radiation, or irradiation under ultraviolet radiation in the presence of a photoinitiator.
• silane crosslinking in the presence of a crosslinking agent in the second composition is preferred since it avoids the use of specific additional equipment such as lamps or irradiation chambers for cross-linking under radiation, or salt bath lines or steam tubes for peroxide crosslinking.
• the second composition comprises only the polymer matrix, and, if necessary, the components intended to crosslink said second composition such as, for example, a crosslinking agent, and thus form the second crosslinked layer.
• a crosslinking agent such as, for example, a crosslinking agent
• first polymeric layer and / or the second polymeric layer of the invention may contain additives that are well known to those skilled in the art, for example surface-treatment agents, antioxidants, waxes, etc. .etc.
• the method of manufacturing the (electrically) insulating layer, and more generally the electric cable, is well known to those skilled in the art.
• the preferred technique for shaping the first and second compositions is extrusion using an extruder.
• the first and second compositions may be extruded in two successive steps or concomitantly. In the latter case, we speak of co-extrusion.
• the crosslinking of the second layer is typically carried out after the extrusion shaping of the second composition.
• the crosslinking step is typically either directly after the extrusion forming step of the first composition or after the extrusion forming step of the second composition.
• the first and second layers of the invention are preferably directly in contact with each other, or in other words the insulating layer comprises no intermediate layer between the first layer and the second layer.
• the insulating layer can then be defined as a "bilayer".
• the electrical cable of the invention may further comprise an outer sheath surrounding the isolated electrical conductor or conductors.
• This outer sheath is well known to those skilled in the art. It can burn completely locally and turn into residual ash under the effect of the high temperatures of a fire without spreading the fire.
• the material that composes the outer sheath may be, for example, a polyolefin-based polymer matrix and at least one hydrated flame retardant mineral filler selected in particular from metal hydroxides such as, for example, magnesium dihydroxide or aluminum trihydroxide.
• the outer sheath may be a tubular sheath or a so-called "jamming" sheath, these two types of sheath being well known to those skilled in the art.
• the tubular sheath is preferred to ensure a circular shape of the cross section of the cable, while the sheath is preferred when the insulated electrical conductors are arranged in parallel to each other in the same plane. In all cases, the outer sheath is conventionally obtained by extrusion.
• the electric cable when the electric cable comprises an outer sheath as defined above, the electric cable may further comprise voids provided between the outer sheath on the one hand, and the isolated electrical conductor or conductors go.
• the outer sheath is preferably tubular.
• the electric cable when the electric cable comprises an outer sheath as defined above, the electric cable may further comprise a stuffing material (or stuffing) between the outer sheath on the one hand, and the isolated electrical conductor or conductors on the other hand.
• a stuffing material or stuffing
• This stuffing material is well known to those skilled in the art and is intended to ensure a cylindrical shape to the cable over its entire length.
• the stuffing consists for example of a polyolefin-based polymer matrix in which mineral fillers such as for example calcium carbonate have been added, and particularly hydrated flame retardant fillers as described above. To obtain greater ash cohesion of the stuffing material, the use of hydrated flame retardant mineral fillers combined with phyllosilicate mineral fillers is preferred.
• the outer sheath may be jamming, especially when the electric cable does not comprise any empty space or stuffing material.
• the electrical cable or in other words the elements that make up said electric cable, preferably does not comprise halogenated compounds.
• first polymeric layer (or inner layer) and the second crosslinked polymeric layer (or outer layer) do not comprise a halogenated compound.
• Another object according to the invention is a method of manufacturing an electric cable as described above according to the invention, characterized in that it comprises the steps of: i. forming the insulating layer as described above around an electrical conductor, ii. optionally, assembling at least two insulated electrical conductors as obtained in step i, iii. optionally, extruding a stuffing material as defined above around the isolated electrical conductor or conductors of step i or ii, and iv. optionally, extruding an outer sheath as defined above around the isolated electrical conductor (s) of step i, ii, or iii.
• the thickness of the first layer ranges from 0.10 mm to
• the thickness of the second layer (outer layer) ranges from 0.05 mm to 1.50 mm, especially when the
• the thickness of the first layer is preferably from 0.30 mm to 0.80 mm, and more preferably to 0.60 mm.
• the thickness of the second layer is preferably from 0.10 mm to 0.50 mm.
• the thickness of the first layer is preferably from 0.30 mm to 0.90 mm. In this case, the thickness of the second layer is preferably 0.10 mm to 0.60 mm.
• the thickness of the first layer is preferably from 0.35 mm to 1 mm.
• the thickness of the second layer is preferably 0.10 mm to 0.70 mm.
• Figure 1 shows a schematic cross-sectional view of an electric cable according to a first embodiment according to the invention.
• FIG. 2 represents a schematic cross-sectional view of an electric cable according to a second embodiment in accordance with the invention.
• FIG. 3 represents a schematic cross-sectional view of an electric cable according to a third embodiment in accordance with the invention.
• the electric cable shown in Figure 1 comprises three insulated electrical conductors 1,2a, 2b and an outer sheath 3 surrounding all three isolated electrical conductors assembled in particular in twist, the insulated electrical conductors being of substantially circular cross section.
• Each of the three insulated conductors consists of an electrical conductor 1 surrounded by a first insulating layer 2a (inner layer) and a second insulating layer 2b (outer layer) directly in contact with said first insulating layer 2a.
• the first and the second insulating layer 2a, 2b are as defined in the present invention.
• the outer sheath 3 provides empty spaces 4 between it and all the insulated electrical conductors that it surrounds.
• This outer sheath 3 is tubular since it has an annular shape in cross section.
• the outer sheath 3 is made from a flame retardant composition comprising a polymer matrix based on polyolefin.
• the electric cable shown in Figure 2 comprises five insulated electrical conductors 1,2a, 2b or 1,2b and an outer sheath 3 surrounding all five insulated electrical conductors, the insulated electrical conductors being of substantially circular cross section.
• Four of the five insulated electrical conductors 1,2a, 2b are respectively surrounded by a first insulating layer 2a (inner layer) and by a second insulating layer 2b (outer layer) directly in contact with said first insulating layer 2a.
• the first and the second insulating layer 2a, 2b are as defined in the present invention.
• the isolated electrical conductor 1,2c remaining is typically grounded. It comprises an electrical conductor surrounded by an insulating layer 2c of polymeric type. This layer may be a monolayer or a bilayer, for example of the same nature as the first layer 2a and / or the second layer 2b of the invention.
• the five insulated conductors are assembled, and in particular twisted, around a reinforcing rod 5.
• a stuffing material 6 surrounds all five isolated electrical conductors. Finally, an outer sheath 3 is extruded around all five electrical insulated conductors and the stuffing material.
• FIG. 3 represents an electric cable according to the invention in which the isolated electrical conductors 1,2a, 2b, four in number in this embodiment. embodiment, are arranged in parallel with each other in the same longitudinal median plane P of the electric cable.
• the set of insulated electrical conductors thus formed forms a strip of insulated electrical conductors, this strip being covered with an outer sheath 3 in order to maintain the insulated electrical conductors 1,2a, 2b in the longitudinal median plane P.
• Electrical cables have been made with electrical conductors surrounded by different types of insulating layers according to the prior art and according to the invention.
• the structure and nature of these cables are detailed in Table 1 below, broken down into two tables la and Ib.
• Each of the electrical cables comprises N insulated electrical conductors including an electrical conductor connected to the ground.
• the NI electrical conductors are detailed in table la, while said insulated electrical conductor grounded is detailed in Table Ib.
• the term "ceramizing thermoplastic layer 1" refers to a layer obtained from an uncrosslinked EVA material comprising from 100 to 200 parts by weight of a mixture of two refractory fillers such as mica muscovite (50 to 150 parts by weight) and CaO (5 to 50 parts by weight), and 5 to 50 parts by weight of zinc borate, parts by weight being based on 100 parts by weight of EVA ;
• “Ceramicizing thermoplastic layer 2” refers to a layer obtained from an uncrosslinked PEO material having from 100 to 200 parts by weight of magnesium oxide and from 5 to 50 parts by weight of zinc borate, the parts by weight being expressed relative to 100 parts by weight of PEO;
• “Ceramicizing thermoplastic layer 3” refers to a layer obtained from an uncrosslinked PEO material having from 100 to 200 parts by weight of muscovite mica and from 5 to 50 parts by weight of zinc borate, the parts by weight being expressed relative to 100 parts by weight of PEO;
• “Ceramicizing thermoplastic layer 4" refers to
• Each of the cables referenced 1 to 7 in Table 1 will undergo fire resistance tests.
• the fire resistance tests are carried out according to the following two standards: IEC 60331-21 and DIN 4102-12.
• the IEC 60331-21 standard consists of subjecting an electric cable to its nominal voltage when it is suspended horizontally over a flame of at least 75O 0 C for a determined period of time but without mechanical stress. This period is checked if there is a short-circuit or breakage of the electrical conductors. The test is successful when there is no short circuit or breakage of the electrical conductors during the test and the next 15 minutes. The electrical cable that has passed the test for 30 minutes is then classified FE30. When it passes the test for 90 minutes or 180 minutes, it is respectively classified FE90 and FE180.
• DIN 4102-12 consists in subjecting an electrical cable with its fixing devices in an oven with a minimum length of 3 meters for a specified period of time according to a standard temperature curve (ISO 834).
• the electrical cable and its fasteners are subject to the maximum permissible weight and specified loads. Electrical conductors are under their operating voltage must not break or give rise to short circuits otherwise the test would be considered a failure.
• the electrical cable having passed the test for 30 minutes at 842 0 C is then classified E30. When it passes the test for 60 minutes at 945 0 C or for 90 minutes at 1006 0 C, it is then respectively classified E60 and E90. This type of test close to the reality of a fire relates not only to the electric cable but also to the fastening systems of said cable.
• Table 2 below shows the very satisfactory results of the fire resistance tests of the electric cables according to the present invention (cables referenced 1 to 5 and 9 to 11) in accordance with the IEC 60331-21 standard. It can also be noted that even without jamming, the cable referenced 3 according to the present invention satisfactorily satisfies this standard.
• the cables referenced 1 to 5 and 9 to 11 have fire resistance properties at least equivalent to or even better than the cable referenced 6, the cost of which is much higher (because of the presence of polyorganosiloxane in the insulating layers of electrical conductors).
• the cables referenced 2, 4 and 8 in Table 1 will undergo electrical resistance tests, the outer sheaths of said cables being previously removed. Electrical resistance tests are performed according to IEC 60502-1 (paragraph 17.2).
• the IEC 60502-1 standard consists in immersing a ring of insulated electrical conductors of at least 5 meters in water at the maximum temperature of the electrical conductors in normal service (eg 9O 0 C) for at least 1 hour before 'trial. Then a DC voltage between 80V and 500V is applied between the ring of isolated electrical conductors and water for a sufficient time (between 1 and 5 minutes). Finally, the transverse resistivity is calculated from the insulation resistance according to the following formula:
• Table 3 below shows the very satisfactory results of the electrical resistance tests of the electric cables according to the present invention (cables referenced 2, 4 and 10) unlike the cable referenced 8 according to the prior art.
• the standard NF EN 60811-2-1 describes the measurement of the hot flow of a material under load.
• the corresponding test is commonly referred to as the Anglicism Hot Set Test.
• test piece of material with a mass corresponding to the application of a stress equivalent to 0.2 MPa, and placing the assembly in an oven heated to 200 +/- 1 0 C for a duration of 15 minutes. At the end of this period, the hot elongation under load of the test piece, expressed in%, is recorded. The suspended mass is then removed, and the test piece is kept in the oven for another 5 minutes. longer remaining permanent, also called remanence, is then measured before being expressed in%.

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