EP3142125B1 - Cable - Google Patents

Description

The invention relates to a cable, in particular a cable for connecting photovoltaic modules, which is suitable for laying in damp environments or in environments in which the cable is exposed to moisture.

In practical use, electrical or optical cables and lines should withstand different influences, in particular mechanical and chemical influences. For various areas of application, good fire resistance of the cables is also required in order to maintain functionality in the event of fire. In DIN 4102, the functional integrity of cable ducts is divided into classes. The class designation is based on the duration within which functional integrity is to be guaranteed as follows. Cables and lines that are used to maintain functionality in the event of fire have a burning behavior in accordance with IEC 60332-1 (flame-retardant) or IEC 60332-3 (highly flame-retardant).

The individual functional units of the cable, the electrical or optical conductor, the conductor insulation, any shielding and the cable jacket must therefore be designed in accordance with the requirements.

There are high demands on long-term stability, especially in the case of cables that are connected to photovoltaic modules, since continuous operation over several years (with a high direct current load) should be guaranteed. The cables must also be halogen-free and flame-resistant. In this area of application, cables are often laid underground. The soil is naturally permeated with moisture, so that the cables laid - especially their outer sheath - are often constantly exposed to high levels of moisture and wetness. The moisture can affect the cable in various ways damage. For example, there is a risk that water-soluble additives in the outer jacket will be washed out over time. Additives, for example flame retardants, are added to the outer jacket in order to improve a desired property and / or resistance of the base material. If these additives are washed out, the properties in question, in particular the resistance, are lost, so that the cable can no longer be operated as intended and the requirements are no longer met.

The permanent exposure to moisture can also impair the insulation properties of the outer jacket and / or the insulation layer (s) inside the cable, so that fault currents, in particular leakage currents, and the associated failure of the system connected to the cable can occur. In the case of cables used in communication technology, signal interference, such as increased attenuation or crosstalk, can occur.

If the cable is stored for a long time in a damp or wet environment, moisture or water can diffuse into the interior of the cable transversely to the longitudinal axis of the cable and damage the internal cable components.

From the DE10131569 a cable that can be laid in moist soil and in water is known. The cable comprises a very thick layer of polyethylene, at least 35mm thick, which is not flame-retardant, but rather easily combustible. The cable is made flame-retardant by applying a thin external fire protection layer. If the thin external fire protection layer is damaged, there is a risk that the underlying polyethylene layer will be set on fire. Due to the large proportion of non-flame-retardant polyethylene in the total cable volume, a Spread fire quickly along the cable as there is a lot of combustible material available. This is a security risk.

From the EP1398799A2 a cable for movable electrical loads is known. A powdery separating layer made of stearate or cellulose is attached between the insulated wires and the inner jacket, which ensures relative mobility between the wires and the inner jacket. The application of separating layers in powder form is associated with a high manufacturing cost. In addition, a great deal of effort must be made during production in order to avoid distribution of the powder over large areas of the production area.

From the DE102012212205A1 a flame-retardant container with a gas-permeable outer shell for an electrical conductor is known. The use of the container is impractical because it is very bulky.

From the EP2669901A1 a cable with a wear indicator is known. The cable is not suitable for use in a damp environment. In addition, the cable quickly fails in the event of a fire.

From the EP0809261A2 a fireproof cable with a layer of a flame retardant material is known. The cable is not suitable for use in a damp environment. EP 2656357 describes a cable covered with a cross-linked polyolefin layer to inhibit water diffusion.

The present invention is therefore based on the object of creating an improved cable that can be laid in damp environments, in particular in the ground.

In particular, the cable should be long-term resistant to moisture and water and minimize the transverse diffusion of water and moisture into the interior of the cable.

Furthermore, the cable should be flame-retardant in accordance with IEC 60332-1-2.

In addition, it should be possible to manufacture the cable simply, inexpensively and in a few steps.

This object is achieved with a cable which has the features specified in claim 1. Advantageous embodiments of the invention are specified in further claims.

The cable, which is particularly suitable for connecting photovoltaic modules to an energy network, comprises at least one electrical and / or at least one optical conductor, at least one insulation layer that encloses the at least one conductor, and an outer jacket that encloses the aforementioned conductor and the insulation layer encloses.

According to the invention, a diffusion barrier layer is arranged between the outer jacket and the insulation layer. The diffusion barrier layer is designed in such a way that the transverse diffusion of water and moisture into the interior of the cable is prevented or at least significantly reduced. Preferably, a reduction in the diffusion of water and Moisture reached by at least a factor of 100, more preferably by at least a factor of 1000, compared to a cable without a diffusion barrier layer. By preventing or at least greatly reducing the penetration of water and moisture into the interior of the cable, the internal cable components, in particular electrical conductors and the insulation layer, are protected from damage and premature aging, which extends the service life of the cable. Malfunctions, such as increased attenuation, crosstalk, energy losses or even sporadic disturbances that are difficult to localize, can be avoided in particular in the case of communication cables.

The properties of the cable can advantageously be selected by appropriately dimensioning the cable. In addition, the manufacturing effort and the material costs can be reduced. In a preferred embodiment, the diffusion barrier layer is thinner than the insulation layer and / or thinner than the outer jacket. By using a thin diffusion barrier layer, only a minimum of easily combustible material is used, so that in the event of a fire only a small proportion of the volume of the cable is combustible. In particular, in the event of mechanical damage to the preferably fire-resistant, flame-retardant or flame-retardant outer jacket, the operational reliability of the cable can thus be increased.

The diffusion barrier layer preferably has a nominal thickness of at least 0.1 mm. The insulation layer and the outer jacket preferably have a nominal thickness of at least 0.5 mm. The thickness of the diffusion barrier layer, insulation layer and outer jacket is preferably matched to the cross section of the electrical conductor and increases with increasing cross-section of the electrical conductor or conductors, possibly proportional to.

The outer jacket, diffusion barrier layer and insulation layer are preferably extrusion products. All layers are preferably manufactured on a cable extrusion line, which enables efficient production.

In a further preferred embodiment, the insulation layer and the diffusion barrier layer are manufactured by coextrusion in a single production step or are applied to the internal materials. In a further preferred embodiment, the diffusion barrier layer and the outer jacket are manufactured by coextrusion in a single production step or are applied to the internal materials.

The diffusion barrier layer is preferably made from a non-polar and / or hydrophobic polymer material. The use of a non-polar and / or hydrophobic material reduces the diffusion even through fine pores or manufacturing defects in the diffusion barrier layer due to capillary forces. The diffusion barrier layer is manufactured in such a way that an uninterrupted layer that is as defect-free as possible is formed.

In a preferred embodiment, the polymer material for the diffusion barrier layer comprises exclusively or mainly polyolefins, in particular polyethylene, polypropylene or mixtures of polyethylene and polypropylene. In a particularly preferred embodiment, the polymer material for the diffusion barrier layer is crosslinked, preferably by electron beam crosslinking and / or silane crosslinking. Networking improves long-term stability.

The cable according to the invention preferably comprises at least two electrical conductors which, in a further preferred embodiment, are each surrounded by a shield. Cables according to the invention can be used in different areas for different applications. Cables according to the invention can be equipped with optical conductors or electrical conductors or a combination thereof.

In a particularly preferred embodiment, the outer jacket is flame-retardant in accordance with the IEC 60332-1-2 standard. For this purpose, flame-retardant additives, preferably aluminum hydroxide, magnesium hydroxide, zinc borates, ammonium sulfate or phosphate-based materials, are added to the polymer material for the outer jacket. These additives are preferably at least largely halogen-free.

In order to improve the flame-retardant or flame-retardant properties of the cable in the event of fire, in a further preferred embodiment, flame-retardant or flame-retardant additives are added to the outer jacket and the inner jacket and / or the insulation layer. Even if the outer jacket is completely destroyed by the action of a flame, the inner jacket and / or the insulation layer can protect the electrical line from damage for a longer period of time. Both the flame-retardant or flame-retardant additive for the outer jacket and the flame-retardant or flame-retardant additive for the inner jacket and / or the insulation layer are preferably at least largely halogen-free.

In a preferred embodiment, the outer jacket and the inner jacket and / or the insulation layer comprise different flame-retardant or flame-retardant additives. The inner jacket and / or the insulation layer particularly preferably comprises at least one higher quality additive, which gives better flame-retardant or flame-retardant properties than additives that are added to the outer jacket. Higher-quality additives, with which excellent flame-retardant or flame-retardant properties are achieved, are usually more expensive than additives with less good technical properties. Since the additive in the outer sheath can be washed out over time, the use of a high-quality additive in the outer sheath is less useful for long periods of operation, as the degradation of the additives disadvantageously changes the original properties of the outer sheath and thus of the cable. According to the invention, high-quality additives are therefore added to at least one of the layers enclosed by the outer jacket, for example the inner jacket and / or further insulation layers. Due to the diffusion barrier layer, the inner jacket and / or the further insulation layers, which are provided with the higher quality additive, are better protected in the long term, so that the high quality additive and the associated high quality properties of the cable are preserved for longer. The use of the at least one high-quality additive in the inner jacket and / or the further insulation layer leads to a reduction in production costs compared to the use of this high-quality additive in the outer jacket.

Metal hydroxides are preferably used as additives. In a preferred embodiment, the outer jacket comprises aluminum trihydrate (ATH) and the inner jacket and / or the insulation layer comprise magnesium dihydrate (MDH).

Metal hydroxides such as aluminum hydroxide or magnesium hydroxide split off water in an endothermic process in the event of a fire. The endothermic conversion process requires between 1000 and 1300 J / g, depending on the source of the ATH or MDH. With ATH the reaction takes place from approx. 200 ° C, with MDH from approx. 300 ° C.

ATH is therefore often used in materials with processing temperatures below 220 ° C, while MDH is used for higher processing temperatures up to 300 ° C. For the present use, however, it is essential that the additive with the higher transformation temperature, preferably MDH, provides the inner layers with flame protection even at higher temperatures and is supported by the outer jacket with its additives.

Fig. 1

einen Querschnitt durch ein erfindungsgemässes Kabel 10 in einer ersten Ausgestaltung; und

Fig. 2

einen Querschnitt durch ein erfindungsgemässes Kabels 10 in einer weiteren bevorzugten Ausgestaltung.

The invention is explained in more detail below with reference to drawings. It shows:

Fig. 1

a cross section through a cable 10 according to the invention in a first embodiment; and

Fig. 2

a cross section through a cable 10 according to the invention in a further preferred embodiment.

Fig. 1 shows a cross section of a cable 10 according to the invention. An electrical conductor 1 is surrounded by a uniform insulation layer 2. A diffusion barrier layer 3 is applied to the insulation layer 2. An outer jacket 4 is applied to the diffusion barrier layer 3. Alternatively, an optical conductor 1 can be used instead of the electrical conductor 1. Likewise, further polymer-based layers or braided shields can be arranged between the insulation layer 2 and the diffusion barrier layer 3 or between the diffusion barrier layer 3 and the outer jacket 4, which are used for shielding, for example.

Fig. 2 shows a cross section of a cable 10 according to the invention in a further preferred embodiment. Several electrical or optical conductors 1 are each enclosed by an insulation layer 2. The insulated conductors 1 are connected to one another by an inner jacket 6 or in an inner jacket 6 adored. A diffusion barrier layer 3 is attached to the inner jacket 6. An optional shield 5 is preferably arranged between the diffusion barrier layer 3 and the outer jacket 4. The optional shield 5 can also be arranged between the inner jacket 6 and the diffusion barrier layer 3. The number of conductors 1 can be selected as required.

The cables according to FIGS. 1 and 2 consist of inner and outer cable layers, which preferably comprise flame-retardant or flame-retardant additives that differ from one another in terms of their properties and possibly also the procurement costs. The outer sheath 4 forms the outermost cable layer, which preferably comprises a first flame-retardant or flame-retardant additive. The inner jacket 6 or the at least one insulation layer 2 preferably comprise a second flame-retardant or flame-retardant additive.

At least one flame-retardant or flame-retardant additive can also advantageously be provided for each of the cable layers 4, 6, 2. The inner jacket has, for example, a second and the at least one insulation layer has a third flame-retardant or flame-retardant additive.

The at least one first flame-retardant additive is preferably made more cost-effectively, possibly from more cost-effective materials, than the at least one second or third flame-retardant additive. In a further preferred embodiment, the at least one first flame-retardant additive is subject to a conversion process at a lower temperature than the at least one second or third flame-retardant additive in the event of a fire.

The first flame-retardant additive is preferably ATH or comprises a predominant portion of ATH and the second sludge-resistant additive is preferably MDH or comprises a predominant portion of MDH. If two inner layers or a middle and an innermost layer are provided, the innermost layer preferably comprises a high quality metal hydroxide or metal hydroxide mixture, preferably MDH, and the middle layer a metal hydroxide mixture with a high quality first metal hydroxide, preferably MDH, and a lower quality second metal hydroxide, preferably ATH, which are preferably mixed in a ratio in the range of 40:60 to 60:40.

List of reference symbols

1

electrical conductor

2

Insulation layer

3

Diffusion barrier

4th

Outer jacket

5

shielding

6th

Inner jacket

10

electric wire

Claims (8)

1. Cable (10) for the electrical connection of photovoltaic modules to an energy network, with

   - at least one electrical and/or at least one optical conductor (1);

   - at least one insulation layer (2) which encloses the conductor (1); and

   - An outer jacket (4) which encloses the conductor (1) and the insulation layer (2);

   characterized in that, a diffusion barrier layer (3) is arranged between the outer jacket (4) and the insulation layer (2), which is designed in a way to prevent or at least strongly reduce lateral diffusion of water and humidity towards the inside of the cable and that the diffusion barrier layer (3) is thinner than the insulation layer (2) and/or that the diffusion barrier layer (3) is thinner than the outer jacket (4) and that the diffusion barrier layer (3) is made from a non-polar polymer material, preferably a polyolefin, and that the polymer material for the diffusion barrier layer (3) is crosslinked and that the conductor (1) with the corresponding insulation layer (2) is enclosed by an inner jacket (6) and that at least one inner or outer cable layer, like the outer jacket (4) and the inner jacket (6) or the outer jacket (4) and the insulation layer (2), each comprise a flame-retardant or flame-proof additive, which is at least mostly free from halogens, and that the outer jacket (4) is flame-retardant according to Norm IEC 60332-1-2.
2. Cable (10) according to claim 1, characterized in that at least two optical or electrical conductors (1) are provided, which are preferably jointly surrounded by a shield (5).
3. Cable (10) according to one of claims 1 or 2, characterized in that the outer jacket (4), the diffusion barrier layer (3), the optionally present inner jacket (6) and / or the at least one insulation layer (2) are extrusion products.
4. Cable (10) according to one of claims 1 - 3, characterized in that the insulation layer (2), optionally the inner sheath (6), and the diffusion barrier layer (3) are the product of a common manufacturing step and / or that the diffusion barrier layer (3) and the outer jacket (4) are the product of a common manufacturing step.
5. Cable (10) according to claim 4, characterized in that the insulation layer (2), optionally the inner jacket (6), and the diffusion barrier layer (3) are the product of a coextrusion and / or that the diffusion barrier layer (3) and the outer jacket (4) are the product of a coextrusion.
6. Cable (10) according to claim 5, characterized in that the outer and the inner cable layer comprise the same flame-retardant additives or that the outer cable layer comprises at least one first flame-retardant additive and the inner cable layer comprises at least one second flame-retardant additive, the first and second flame-retardant additives Differentiate additives from one another.
7. Cable (10) according to claim 6, characterized in that the at least one first flame-retardant additive is manufactured more cost-effectively, preferably from less expensive materials, than the at least one second flame-retardant additive and / or that the at least one first flame-retardant additive in the event of fire is subject to a conversion process at a lower temperature as the at least one second flame-retardant additive.
8. Cable (10) according to claim 6 or 7, characterized in that the at least one first flame-retardant additive consists of ATH or a predominant portion of ATH and that the second flame-retardant additive consists of MDH or a predominant portion of MDH.

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