KR101688505B1 - Electric cable adapted for ensuring the continuity of power distribution in the event of fire - Google Patents

Abstract

The invention comprises at least one insulated electrical conductor, each of the insulated electrical conductors comprising an electrical conductor surrounded by an insulating layer, the insulating layer comprising a first polymer layer (2a) surrounding the electrical conductor, , Said first layer (2a) being obtained from a first composition comprising a polymer matrix formed of a thermoplastic polymer and at least one ceramic-forming filler, said insulating layer comprising a crosslinked Characterized in that it further comprises a second polymer layer (2b), said second layer (2b) being obtained from a second composition comprising a polymer matrix comprising a polyolefin substantially free of ceramic forming fillers or halogenated compounds Power cables.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to an electric cable suitable for ensuring continuity of electric power distribution in a fire,

The present invention relates to a power cable comprising at least one insulated electrical conductor capable of ensuring continuity of power distribution in the event of a fire.

The present invention is generally, but not exclusively, applied to the refractory, particularly non-halogen, security cable field, which can operate for a given time in a fire state without propagating a fire or generating significant smoke. These security cables are in particular power transmission cables or low frequency transmission cables, such as control or signal transmission cables.

One of the major problems in the cable industry is improving the operation and performance of the cable under extreme thermal conditions, especially during thermal conditions during the fire. In essence, for security reasons, it is critical to maximize the performance of the cable to withstand fire, in order to ensure continuity of operation, especially to ensure continuity of emergency evacuation support equipment.

In the event of a fire, the cable must be able to withstand the fire to operate as long as possible and to limit its deterioration. The security cable must also not be harmful to the environment, ie the cable should not spread fire and should not emit toxic and / or opaque smoke when exposed to extreme thermal conditions.

EP 0942439 discloses a non-halogen refractory security cable comprising an assembly of insulated electrical conductors surrounded by an outer jacket. Each insulated electrical conductor is formed by an electrical conductor surrounded by a polymer insulative monolayer obtained from a composition comprising a polymeric material and at least one ceramic-forming filler, To a ceramic state at a high temperature corresponding to a fire condition. The polymeric material of this single insulating layer is selected from polysiloxane (polyorganosiloxane) and an ethylene copolymer or a mixture thereof.

Other non-halogen refractory security cables are known to have electrical conductors surrounded by bilayer polymer insulation. For example, document EP 1347464 describes a double-layer insulating material which can be converted to a ceramic state at a high temperature corresponding to at least a fire condition at the surface. Each of these layers of bilayer insulation comprises an ethylene / octene copolymer and a ceramic formed filler.

However, these security cables of the prior art have been found to be mechanically brittle, even though they have excellent fire resistance properties. In particular, insulated electrical conductors are sensitive to the various mechanical stresses that these cables typically receive during manufacture, transport, handling, installation, or connection. Moreover, in accordance with the IEC 60502-1 standard, its electrical resistance at high temperatures in humid environments is not sufficient due to the presence of ceramic forming fillers.

It is an object of the present invention to provide a method and apparatus for the electrical insulation of a cable, in particular of the risk of mechanically deteriorating an insulated electrical conductor constituting the cable, while still maintaining excellent fire resistance characteristics meeting the IEC 60331-21 standard and improved electrical resistance meeting the IEC 60502-1 standard. And to solve the drawbacks of the prior art by providing a power cable which can be easily handled.

The subject matter of the present invention comprises one or more insulated electrical conductors, each of the insulated electrical conductors having an electrical conductor surrounded by an insulating layer, preferably an electrically insulating layer, which surrounds the electrical conductor Wherein the first layer comprises a polymer matrix based on a thermoplastic polymer and at least one ceramic forming filler, wherein the insulating layer surrounds the first layer Characterized in that said second layer is obtained from a second composition comprising a polymer matrix based on polyolefin substantially free of ceramic forming fillers and halogenated compounds, said second layer being obtained from a second composition comprising a crosslinked second polymer layer have.

In the following,

- the term "first composition comprising a polymer matrix based on thermoplastic polymer" means that the majority of the polymers or polymers used in the first composition (in weight% in the matrix) are one or more thermoplastic polymers;

The term "second composition comprising a polymer matrix based on polyolefin" means that the majority of the polymers or polymers used in the second composition (in weight% in the matrix) are one or more polyolefins.

The term "halogenated compound" also includes any kind of compound including one or more halogen elements such as, for example, a fluoropolymer, or a chlorinated polymer such as, for example, polyvinyl chloride (PVC), a halogenated plasticizer , Halogenated mineral-containing fillers, and the like.

According to the present invention, the crosslinked polyolefin-based second polymer layer (outer layer) mechanically protects the thermoplastic polymer-based first polymer layer (inner layer). This property ensures that the mechanical properties of the cable in the insulation layer of each insulated electrical conductor, in particular the hardness of the insulated electrical conductor constituting the cable, Improves abrasion resistance and tear resistance, facilitates the installation of the cable and makes the cable more robust during its manufacture.

In particular, the insulating layer of the power cable of the present invention has excellent mechanical heat resistance (or hot creep) which meets EN 60811-2-1 standard.

Further, the power cable including the insulating layer according to the present invention satisfies the IEC 60331-21 standard with excellent fire resistance characteristics. Thus, the electrical conductor is protected from fire, in other words, the power cable can ensure high quality refractory operation in terms of at least cohesion of electrically insulating ash.

Another advantage of the insulating layer of the power cable of the present invention relates to electrical resistance. Due to the absence of the ceramic forming filler in the outer layer of the insulating layer of the present invention, the electrical resistance characteristics of the cable at high temperature according to the IEC 60502-1 standard are significantly improved.

Another advantage of the insulating layer of the power cable of the present invention is that it substantially limits the emission of toxic smoke when in an extreme thermal state.

Finally, the present invention thus limited has the advantage of low cost because it allows to significantly restrict or even completely avoid the use of the polyorganosiloxane in the insulating layer of the insulated electrical conductor, while still having very good fire resistance properties have.

The first polymer layer (or inner layer)

According to the present invention, the thermoplastic polymer of the first composition may be advantageously selected from olefin polymers, acrylates or methacrylate polymers, for example vinyl polymers such as polyvinyl chloride and fluoropolymers or mixtures thereof.

As a preferred example, the olefin polymer may be an ethylene homopolymer; Ethylene / octene (PEO) copolymers; Ethylene / vinyl acetate (EVA) copolymers; Ethylene / butyl acrylate (EBA) copolymers; Ethylene / methyl acrylate (EMA) copolymers; Ethylene / ethyl acrylate (EEA) copolymers; Ethylene / butyl acrylate (EBA) copolymers; Ethylene / ethyl acrylate (EEA) copolymers; Ethylene / propylene rubber (EPR) copolymers; Ethylene / propylene / diene monomer (EPDM) copolymers; Or a mixture thereof.

In a preferred embodiment, the polymer matrix of the first composition comprises at least 95% by weight of the thermoplastic polymer, and preferably the polymer matrix comprises at least one thermoplastic polymer.

In another preferred embodiment, the first composition comprises no more than 5 wt% polyorganosiloxane, preferably no more than 2 wt% polyorganosiloxane, and even more preferably, the first composition comprises polyorganosiloxane .

The ceramic forming filler used in the first composition allows the first layer at the surface to be converted to a ceramic state at a high temperature corresponding to the fire condition thereby forming a "ceramicizing" first layer. Thus, the ceramicizable layer provides sufficient insulation when the second layer (outer layer) disappeared as a result of the combustion phenomenon.

The ceramic forming filler according to the present invention may be selected from a meltable 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.

In particular, the meltable ceramic filler has a melting point lower than the high temperature (T), and the refractory filler has a melting point higher than the temperature (T). This temperature T is advantageously at least 750 ° C, and possibly at most 1100 ° C.

Melt possible ceramic filler is a boron oxide (e.g., B ₂ O _3), anhydrous zinc borate (borate) (e.g., 2ZnO · 3B ₂ O ₃₎ or a hydrated zinc borate (e.g., 4ZnOB ₂ O ₃ One or more mineral fillers selected from one of the following: H ₂ O or ₂ ZnO ₃ B ₂ O ₃ .3.5H ₂ O), anhydrous boron phosphate (eg, BPO ₄ ) or hydrated phosphate or precursors thereof. To provide an example, calcium borosilicate may be referred to as a boron oxide precursor.

The fusible ceramic filler generally has a melting point lower than 500 캜 and generates an amorphous phase (e.g., glass) when the temperature exceeds 500 캜.

Refractory filler is magnesium oxide (e.g., MgO), calcium oxide (e.g., CaO), silicon oxide {e.g., SiO ₂ or a modified (quartz)}, aluminum oxide (e.g., Al ₂ O ₃ ), chromium oxide (for example, Cr ₂ O _3), zirconium oxide (e.g., ZrO _2), and for example, montmorillonite, sepiolite, illite, attapulgite, talc, kaolin or mica (e. g., muscovite 6SiO may be a _{2 3Al 2 O 3 K 2 O} · 2H 2 O) and phyllosilicate (phyllosilicate) or at least one mineral filler selected from one of their mixtures such.

Preferably, the ceramic forming filler comprises two refractory fillers, such as, for example, muscovite and one of calcium oxide (CaO) or a precursor thereof (e.g., calcium carbonate CaCO ₃ ) and a refractory filler such as a boron oxide precursor And the like.

The amount of the ceramic forming filler is limited to at least 90 parts by weight of the filler per 100 parts by weight polymer, preferably up to 250 parts by weight of the filler per 100 parts by weight of the polymer, to limit rheological problems in the composition .

In particular, the amount of the ceramic filler capable of being melted may be 5 to 100 parts by weight, preferably 20 to 80 parts by weight, per 100 parts by weight of the polymer in the first composition, and the amount of the refractory filler is preferably 50 to 200 parts by weight, Weight portion.

In a preferred embodiment, the first composition is not cross-linked, i.e. the first layer formed around the electrical conductor is not cross-linked.

Also, in one particular embodiment, the first polymer layer (or inner layer) does not contain any halogenated compounds at all.

The crosslinked second (or outer) polymer layer

The crosslinked second polymer layer differs from the first polymeric layer in that it is "non-ceramicizing" since it does not substantially comprise a ceramic forming filler. The term "substantially" means that the second composition may additionally comprise a ceramic forming filler, but may only be included as an additive. As a result, the second layer may not have properties that can be converted at least from the surface to the ceramic state at a high temperature corresponding to the fire condition, for example when the second composition comprises less than 50 parts by weight of the ceramic forming filler .

The polyolefin of the second composition may advantageously be selected from ethylene homopolymers and copolymers or mixtures thereof.

As a preferable example of the ethylene homopolymer, low density polyethylene (LDPE) may be mentioned.

Ethylene copolymers include ethylene / octene (PEO) copolymers; Ethylene / vinyl acetate (EVA) copolymers; Ethylene / butyl acrylate (EBA) copolymers; Ethylene / methyl acrylate (EMA) copolymers; Ethylene / ethyl acrylate (EEA) copolymers; Ethylene / propylene rubber (EPR) copolymers; And ethylene / propylene / diene monomer (EPDM) copolymers; Or a mixture thereof. Preferred ethylene copolymers include ethylene / vinyl acetate (EVA) copolymers.

Preferably, the polymer matrix of the second composition is different from the polymer matrix of the first composition.

In a preferred embodiment, the polymer matrix of the second composition comprises at least 95% by weight of the polyolefin, and preferably the polymer matrix comprises at least one polyolefin.

In another preferred embodiment, the second composition comprises no more than 5% polyorganosiloxane, preferably no more than 2% polyorganosiloxane, and even more preferably the second composition comprises polyorganosiloxane .

According to a first variant, the second composition may additionally comprise at least one mineral filler different from the ceramic forming filler.

The mineral filler may be a hydrated fire-retarding mineral filler, especially selected from metal hydroxides, such as, for example, magnesium dihydrate (MDH) or aluminum trihydroxide (ATH). The predominantly used fire-retardant mineral fillers are acted upon by physical roots due to decomposition by the endothermic reaction, which results in lowering the temperature of the insulation layer and limiting flame propagation along the cable.

The mineral filler may also be a carbonate such as calcium carbonate.

The amount of mineral filler is limited so that the second composition comprises at least 90 parts by weight of said filler per 100 parts by weight of polymer, preferably at most 200 parts by weight of said filler per 100 parts by weight of polymer .

The crosslinked second polymer layer of the first variant is most advantageous when it is combined with a non-crosslinked first polymer layer that contains only one or more refractory fillers as a ceramic forming filler.

According to a second variant, the second layer is so-called "unfilled ", i. E. In addition to not containing ceramic forming fillers, the second layer contains no hydrated fire- retarding mineral fillers, It does not contain fillers at all.

Crosslinking of the second composition to obtain a crosslinked second layer may be accomplished by crosslinking by photochemical means such as irradiation with ultraviolet light or by irradiation with beta rays in the presence of a photoinitiator, Can be carried out by conventional cross-linking techniques well known to those skilled in the art, such as silane cross-linking in the presence of a cross-linking agent. The silane crosslinking in the presence of a crosslinking agent in the second composition is preferred because it can be used for a radiation lamp for radiation bridging, a salt-bath line for chamber or peroxidic crosslinking, steam tubing) to avoid the use of additional specific equipment.

In a particularly preferred embodiment, the second composition comprises only the polymer matrix and comprises, if necessary, components for forming a crosslinked second layer by cross-linking the second composition, such as, for example, a crosslinking agent. Thus, the latter case is an unfilled crosslinked layer.

Regardless of the first polymer layer and / or the second polymer layer of the present invention, the layers include additives well known to those skilled in the art, such as, for example, surface treatment agents, antioxidants, waxes, can do.

Method for manufacturing insulating layer

Methods for fabricating electrically insulating layers, more generally power cables, are well known to those skilled in the art.

A preferred technique for forming the first composition and the second composition is extrusion using an extruder.

The first composition and the second composition may be extruded in two successive stages or may be extruded at the same time. When extruded at the same time, this technique is called coextrusion.

The second layer is generally crosslinked after the second composition is formed by extrusion.

If the first layer is also crosslinked, the crosslinking step generally occurs immediately after the step of forming the first composition by extrusion or immediately after the step of forming the second composition by extrusion.

The first layer and the second layer of the present invention are preferably in direct contact with each other, that is, the insulating layer does not include an intermediate layer between the first layer and the second layer. Thus, the insulating layer can be defined as "bilayer. &Quot;

Outer jacket

The power cable of the present invention may additionally include an outer electrical jacket surrounding the insulated electrical conductor or conductors. The outer jacket is well known to those of ordinary skill in the art. This can be completely burned in place and converted into residual ash (ash) under the influence of high temperatures during a fire without propagating the fire.

The material comprising the outer jacket may be, for example, a polymer matrix based on a polyolefin and one or more hydrated fire-retarding mineral fillers, especially selected from metal hydroxides such as magnesium dihydrate and aluminum trihydroxide.

The outer jacket can be a tubular jacket or a so-called "filling" jacket, both of which are well known to those of ordinary skill in the art. The tubular jacket is preferred to ensure that the cross-section of the cable has a circular shape, while the fill jacket is preferred when the insulated electrical conductors are arranged in parallel, i.e., one on the other side in the same plane. In both cases the outer jacket is usually obtained by extrusion.

Power cable

According to a first variant, when the power cable comprises the outer jacket described above, the power cable may additionally comprise an empty space provided between the outer jacket on the one hand and the insulated electrical conductor or conductors on the other hand. In this case, the outer jacket is preferably tubular to ensure that the cable has a cylindrical shape over its entire length.

According to a second variant, when the power cable comprises the outer jacket described above, the power cable may additionally comprise a filler material on the one hand between the outer jacket and on the other hand an insulated electrical conductor or conductors.

Such fillers are well known to those skilled in the art and the aim is to ensure that the cable has a cylindrical shape over its entire length.

Which is generally extruded around insulated electrical conductors or conductors. The filling consists of a polyolefin-based polymer matrix with mineral fillers, for example calcium carbonate, and particularly preferably a hydrated fire-retardant filler as described above. In order to better adhere the ash to the fill material, it is preferred to use a hydrated fire-retarding mineral filler combined with a filler silicate type mineral filler.

According to a third variant, when the power cable comprises an outer jacket as described above, the outer jacket may be a fill jacket, especially if the power cable does not contain any voids or fill material.

According to another feature of the invention, in order to ensure a HFFR (non-halogenated permanent) cable, the elements constituting the power cable or the power cable preferably do not contain a halogenated compound.

In particular, the second (or outer) polymer layer that is crosslinked with the first (or inner) polymer layer does not contain any halogenated compound at all.

Method for manufacturing insulating layer

A further subject matter of the present invention is a method of manufacturing a power cable as described above in accordance with the present invention, which comprises the following configured steps:

I. Forming an insulating layer as described above around the electrical conductor;

Ii. Alternatively, assembling the at least two insulated electrical conductors obtained in step (i);

Iii. Alternatively, extruding the fill material as described above around the insulated electrical conductor or conductors of step (i) or (ii); And

Iv. Optionally, extruding the outer jacket described above around the insulated electrical conductor or conductors of step (i), (ii) or (iii).

In a particular embodiment according to the invention, the thickness of the first (inner) layer ranges from 0.10 mm to 1.50 mm, particularly when the cross section of the electrical conductor is in the range of 1.5 mm2 to 4 mm2, The thickness of the layer is in the range of 0.05 mm to 1.50 mm.

According to a first variant of this embodiment, when the cross section of the electrical conductor is 1.5 mm2, the thickness of the first layer is preferably in the range of 0.30 mm to 0.80 mm, in particular in the range of 0.30 mm to 0.60 mm. In this case, the thickness of the second layer is preferably in the range of 0.10 mm to 0.50 mm.

According to the second variant of this embodiment, when the cross section of the electrical conductor is 2.5 mm2, the thickness of the first layer is preferably in the range of 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.

According to the third variant of this embodiment, when the cross section of the electrical conductor is 4 mm2, the thickness of the first layer is preferably 0.35 mm to 1 mm. In this case, the thickness of the second layer is preferably 0.10 mm to 0.70 mm.

Other features and advantages of the present invention will become more apparent with reference to the following embodiments and the accompanying drawings, which are for the purpose of illustration and not of limitation.

1 shows a schematic cross-sectional view of a power cable in a first embodiment according to the present invention.
Figure 2 shows a schematic cross-sectional view of a power cable in a second embodiment according to the present invention.
3 shows a schematic cross-sectional view of a power cable in a third embodiment according to the present invention.

For clarity, the same elements have been indicated by the same reference numerals in the figures. Likewise, only those elements essential to understanding the present invention are shown schematically, and they are not shown to scale.

The power cable shown in Fig. 1 comprises three insulated electrical conductors 1,2a, 2b and, in particular, an outer jacket 3 which surrounds all three insulated electrical conductors twisted together, The conductors have a substantially circular cross-section.

Each of the three insulated conductors is surrounded by an electrical conductor 1 (outer layer) surrounded by a first insulating layer 2a (inner layer) and a second insulating layer 2b (outer layer) in direct contact with the first insulating layer 2a. ). The first and second insulating layers 2a and 2b are as defined in the present invention.

The outer jacket (3) leaves a void (4) between the surrounding set of insulated electrical conductors and the outer jacket. The outer jacket 3 is tubular because its cross-section has an annular shape.

The outer jacket 3 is produced from a fire-retarding composition comprising a polymer matrix based on a polyolefin.

The power cable shown in Figure 2 comprises five insulated electrical conductors (1,2a, 2b or 1, 2c) and an outer jacket (3) surrounding all five insulated electrical conductors, The conductors have a substantially circular cross-section.

Four of the five insulated electrical conductors 1, 2a and 2b are respectively provided with a first insulating layer 2a (inner layer) and a second insulating layer 2b in direct contact with the first insulating layer 2a, (Outer layer). The first and second insulating layers 2a and 2b are as defined in the present invention.

The remaining insulated electrical conductors (1,2c) are typically connected to ground. Which comprises an electrical conductor surrounded by a polymer insulating layer 2c. The layer may be a single layer or a bilayer, for example, of the same properties as the first layer 2a and / or the second layer 2b of the present invention.

The five insulated conductors are assembled, in particular twisted around the rigid member 5.

The filling material (6) surrounds all five insulated electrical conductors.

Finally, the outer jacket 3 is extruded around all five insulated electrical conductors and fillers.

The cylindrical shape, i.e., the circular cross section, of the power cable of the present invention as shown in Figures 1 and 2 is not limiting.

The power cable may have a so-called "flat" cross-section as shown in Fig. Figure 3 shows a power cable according to the invention in which four insulated electrical conductors 1,2a, 2b in this embodiment are arranged side by side parallel to one another in the same longitudinal middle plane P of the power cable . The set of insulated electrical conductors arranged in this way forms an insulated electrical conductor strip which is covered by an outer jacket 3 and which is electrically insulated from the median plane P in the longitudinal direction 1, ).

Example

Power cables have been fabricated with electrical conductors surrounded by various types of insulating layers in accordance with the prior art and the present invention. The structure and characteristics of these cables are shown in Table 1 below by dividing into two Tables 1a and 1b. Each of the power cables comprises N insulated electrical conductors, one of which is connected to ground. N-1 electrical conductors are specified in Table Ia, while insulated electrical conductors connected to ground are detailed in Table Ib.

The structure of the power cable that can be considered to understand Tables 1a and 1b is as shown in FIG.

In Table 1,

- the term "ceramicized thermoplastic layer (1)" refers to a mixture of 100-200 parts by weight of a mixture of two refractory fillers such as muscovite (50-150 parts by weight) and CaO (5-50 parts by weight) (Here, parts by weight are shown for 100 parts by weight EVA), < RTI ID = 0.0 >

- The term "ceramicized thermoplastic layer (2)" refers to a layer obtained from a non-crosslinked PEO material comprising 100 to 200 parts by weight of magnesium oxide and 5 to 50 parts by weight of zinc borate, wherein 100 parts by weight of PEO , ≪ / RTI >

- the term "ceramicized thermoplastic layer (3)" refers to a layer obtained from a non-crosslinked PEO material comprising 100 to 200 parts by weight of muscovite and 5 to 50 parts by weight of zinc borate, wherein 100 parts by weight of PEO , ≪ / RTI >

The term "ceramicized thermoplastic layer (4)" refers to a layer obtained from a non-crosslinked PEO material comprising 100 to 200 parts by weight of magnesium oxide (MgO), wherein parts by weight are shown for 100 parts by weight of PEO,

The term "silicon layer" refers to a layer obtained from a crosslinked polyorganosiloxane material marketed by Wacker under the name R502 / 75,

The term "unfilled XLPE" refers to a crosslinked unfilled polyethylene material available from BOREALIS under the name Visico 4423,

The term "Filled XEVA" refers to a crosslinked EVA material comprising a fire-retardant filler marketed by Padanaplast under the name Cogegum GFR 360,

The term "filled XLPE" refers to a cross-linked polyethylene material comprising a fire-retardant filler marketed by Padanaplast under the name Cogegum GFR 325,

The term "cohesion 1" refers to a HFFR fill material (or filler) marketed by CONDOR under the name CC420,

The term "Adhesion 2 " refers to a HFFR fill material (or filler) sold by CONDOR under the name Confill D-F0704,

The term "fill thickness" refers to the thickness of the fill between the outer periphery of the insulating layer of the insulated electrical conductor and the inner periphery of the outer jacket,

The term "HFFR jacket" refers to a non-crosslinked HFFR polyolefin material available from Polyone under the name ECCOH 5860.

Fire resistance test

Each of the cables labeled 1 through 7 in Table 1 was tested for fire resistance. The fire resistance test was carried out in accordance with two standards, namely IEC 60331-21 and DIN 4102-12.

The IEC 60331-21 standard consists of a power cable receiving a nominal voltage when the power cable is suspended horizontally above a flame with a temperature above 750 ° C for a specified time without mechanical stress. During this time, it is checked whether there is a break or short of the electrical conductor. During the test and for the following 15 minutes, the test passes when there is no break in the electrical conductor and there is no short circuit. Power cables that pass the test for 30 minutes are classified as FE30. If the power cable passes the test for 90 minutes or 180 minutes, the power cable is classified as FE90 to FE180, respectively.

The DIN 4102-12 standard consists of fixing the power cable to a fastener in a furnace with a specific length of more than 3 meters according to a standardized (ISO 834) temperature curve. In addition, the power cable and its fastener are subjected to a maximum permissible weight and a predefined load. Since the electrical conductors are under service voltage, these conductors should not be ruptured or short-circuited, otherwise the test will be considered a failure. Power cables that have passed the test at 842 ° C for 30 minutes are classified as E30. If the power cable passes the test at 945 ° C for 60 minutes or at 1060 ° C for 90 minutes, the power cable is classified as E60 or E90, respectively. This type of test, close to real fire, applies not only to power cables, but also to systems that fix the cables.

Table 2 below shows very satisfactory results of the fire resistance tests carried out on the power cables (cables named 1 to 5 and 9 to 11) according to the invention according to the IEC 60331-21 standard. In particular, it can be noted that the cable named as 3 in accordance with the present invention satisfies the above standard even when it is unfilled.

In addition, the DIN 4102-12 standard is more easily satisfied when filling is present (cables named 1, 2, 4, 5, 10 and 11).

Also, very satisfactory results are observed in the cables named 9-11, wherein each inner layer contains only a refractory filler as a ceramic forming filler.

Considering the results for the cables named 10 and 11, on the one hand, an inner layer containing only a refractory filler as a ceramic-forming filler and a crosslinked outer layer based on an ethylene polymer filled on the other, , Surprisingly satisfies in particular the DIN 4102-12 standard.

Finally, the cables named 1 to 5 and 9 to 11 are not at least as good as the cables named as 6 (due to the presence of the polyorganosiloxane in the insulation layer of the electrical conductor) .

Cable naming One 2 3 4 5 6 7 8 9 10 11 IEC 60331-21 FE180 (> 180 min) FE180 (> 180 min) FE180 (> 180 min) FE180 (> 180 min) FE180 (> 180 min) FE180 (> 180 min) FE90 (> 90 min)
(FE180 failed) FE90 (> 90 min)
(FE180 test not performed) FE180 (> 180 min) FE180 (> 180 min) FE180 (> 180 min) DIN 4102-12 E30 (> 30 min) E30 (> 30 min) failure E30 (> 30 min) E30 (> 30 min) failure failure failure failure E30 (> 30 min) E30 (> 30 min)

Electrical resistance test

The cables labeled 2, 4, and 8 in Table 1 were subjected to an electrical resistance test and the outer jacket of the cable was removed in advance. Electrical resistance testing was performed in accordance with IEC 60502-1 (para. 17.2) standards.

IEC 60502-1 standard specifies that a ring of insulated electrical conductors with a minimum length of 5 meters at a maximum temperature (for example, 90 ° C) for electrical conductors of normal service for at least 1 hour before testing is immersed in water . A DC voltage between 80V and 500V is then applied between the ring of insulated electrical conductor and water for a sufficient time (1 to 5 minutes).

Finally, the transverse resistivity is calculated from the insulation resistance according to the following equation:

ρ = 2πRL / ln (D / d)

here,

rho is the lateral resistance in ohm · m,

R is the insulation resistance in ohms,

L is the length of the insulated conductor in m,

D is the outer diameter of the insulation jacket in mm,

d is the inner diameter of the insulation jacket in mm.

Table 3 below shows very satisfactory results with the electrical resistance tests performed on the power cables (cables named 2, 4 and 10) according to the invention compared to the cables named 8 according to the prior art.

Cable naming 2 4 8 10 At 90 캜, ρ (ohm · m) > 1 x 10 ⁸ 2 x 10 ¹² 6 × 10 ⁶ > 1 × 10 ⁷

Hot creep test

NF EN 60811-2-1 describes the measurement of the hot creep of a material under load. The corresponding test is also commonly referred to as a hot set test.

Specifically, it consists of testing one end of a sample of material having a weight corresponding to the application of an equivalent stress of 0.2 MPa and placing the assembly in an oven heated at 200 (占) 占 폚 for a period of 15 minutes do. After this time, the hot elongation under load of the sample expressed in% is recorded. Thereafter, the suspended weight is removed and the sample is placed in the oven for an additional 5 minutes. The residual permanent elongation, previously expressed in%, which is also referred to as the set, is then measured.

It should be recalled that as the material is more crosslinked, the elongation and set values become lower. It should also be noted that if the sample ruptures under the interaction of mechanical stress and temperature during the test, the results of the test will be considered logically a failure.

The test was carried out on an insulating layer of N-1 electrical conductors of the cables named 1 to 11. The results are given in Table 4 below.

Cable naming One 2 3 4 5 6 7 8 9 10 11 Hot creep test Pass Pass Pass Pass Pass Pass failure failure Pass Pass Pass

The insulating layers 1 to 5 and 9 to 11 according to the present invention are continuously exposed to NF EN 60811-2-C in that the elongation and set under load are less than 175% and 25% 1 standard. ≪ / RTI > It should be recalled that although the double layer insulation of the cable named 6 also satisfactorily passes the above standard it has inferior refractory properties than the economical cable according to the invention because it contains polyorganosiloxane.

Claims (15)

A power cable comprising at least one insulated electrical conductor,
Each of said insulated electrical conductors comprising an electrical conductor surrounded by an insulating layer, said insulating layer comprising a first polymer layer (2a) of the ceramizable layer type surrounding the electrical conductor, said first polymer layer (2a ) Is obtained from a first composition comprising a polymer matrix based on a thermoplastic polymer and at least one ceramic formed filler,
Wherein the insulating layer further comprises a crosslinked second polymer layer (2b) surrounding the first polymer layer, wherein the second polymer layer (2b) comprises less than 50 parts by weight of ceramic forming filler and the halogenated compound ≪ / RTI > wherein the second composition is obtained from a second composition comprising a polyolefin-based polymer matrix that does not include a polyolefin-based polymer matrix. The method according to claim 1,
Wherein the thermoplastic polymer of the first composition is selected from an olefin polymer, an acrylate or methacrylate polymer, a vinyl polymer and a fluoropolymer, or a mixture thereof. The method according to claim 1,
Wherein the ceramic forming filler is selected from a meltable ceramic filler and a refractory filler, or a mixture thereof. The method of claim 3,
Wherein the meltable ceramic filler has a melting temperature lower than a temperature (T) of 750 占 폚 or higher. The method according to claim 3 or 4,
Wherein the meltable ceramic filler is at least one mineral filler selected from boron oxide, anhydrous or hydrated zinc borate, anhydrous or hydrated zinc phosphate, and precursors thereof. The method of claim 3,
Wherein the refractory filler has a melting temperature higher than a temperature (T) of 750 DEG C or higher. The method according to claim 3 or 6,
Wherein the refractory filler is at least one mineral filler selected from magnesium oxide, calcium oxide, silicon oxide, aluminum oxide, chromium oxide, zirconium oxide, and phyllosilicate. The method according to claim 1,
Wherein the first composition comprises at least 90 parts by weight of a ceramic formed filler per 100 parts by weight of polymer. The method according to claim 1,
Wherein said first polymer layer (2a) is not crosslinked. The method according to claim 1,
Wherein the polyolefin of the second composition is selected from ethylene homopolymers and copolymers, or mixtures thereof. The method according to claim 1,
Wherein the first composition and / or the second composition comprises no more than 5 wt% polyorganosiloxane. The method according to claim 1,
Wherein the crosslinking of the second composition to obtain a crosslinked second polymer layer (2b) is a silane crosslinking in the presence of a crosslinking agent in the second composition. The method according to claim 1,
Further comprising an outer jacket (3) surrounding the insulated electrical conductors or conductors. 14. The method of claim 13,
Characterized in that it further comprises a filler material (6) between the outer jacket (3) and the insulated electrical conductor or conductors. The method according to claim 1,
Wherein the power cable does not contain a halogenated compound.

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