Method for producing a single-core cable

Abstract

The invention relates to a method for producing a single-core cable, in which method the conductor shield (2), the insulation (3) and the insulating shield (4) are extruded simultaneously as three layers in a single operation, after which the semiconducting intumescent strip (5) is laid onto the insulating shield (4) longitudinally with an overlap or optionally helically with an overlap, while a copolymer-coated aluminum strip (6) having a thickness of at least 0.30 mm is laid in the longitudinal direction with an overlap, followed by an extrusion of the HDPE coating (8), wherein the thickness of the copolymer is between 0.04 and 0.06 mm.

Description

[0001]

[0002] Method for manufacturing a single-core cable

[0003] The invention relates to a method for manufacturing a single-core cable with aluminium conductors, with insulation made of cross-linked polyethylene and a sheath made of thermoplastic polyethylene and a shield made of special aluminium tape.

[0004] The aim of the invention is to develop a method for manufacturing a single-core cable, in which a particularly simple, cost-effective, flexible and robust cable can be produced.

[0005] According to the invention, this objective is achieved by simultaneously extruding a conductor shield, an insulation layer, and an insulating shield as three layers in a single operation, after which a semiconducting, intumescent tape is laid longitudinally with an overlap or spirally with an overlap onto the insulating shield, while a copolymer-coated aluminum tape with a thickness of at least 0.30 mm is laid longitudinally with an overlap, followed by extrusion of the HDPE sheath or HDPE coating, wherein the thickness of the copolymer is between 0.04 mm and 0.06 mm.

[0006] The invention provides a method for manufacturing a single-core cable in which, by suitable selection of the thickness and width of the aluminum foil, a short-circuit current carrying capacity of the aluminum strip can be achieved that corresponds to that of a copper wire return conductor with the same cross-section as the aluminum strip.

[0007] The manufacture of a single-core cable may include extruding the conductor shield, the insulation, and the insulating screen simultaneously as three layers in a single operation, after which the intumescent semiconducting tape is laid longitudinally with an overlap or, if necessary, spirally with an overlap onto the insulating screen, and the copolymer-coated aluminum tape, with a thickness of at least 0.30 mm and a width of at least 82 mm, is laid longitudinally with an overlap, and subsequently the HDPE sheath is extruded.

[0008] Surprisingly, it has been found that the exceptionally thin HDPE sheath provides sufficient insulation while simultaneously offering excellent flexibility. Despite this, no adhesion problems arise with the underlying aluminum strip. Thus, the invention enables a particularly flexible and easy-to-handle embodiment. A further advantage of the HDPE sheath thickness according to the invention is its ease of manufacture, resulting in a cost-effective design. Therefore, it is particularly advantageous to select a copolymer thickness between 0.04 mm and 0.06 mm. Preferably, the HDPE sheath is implemented as an HDPE coating.

[0009] This cable design is particularly advantageous because it significantly reduces the carbon footprint when manufacturing a cable shield from aluminum strip. This can result in a reduction of approximately 30% to 45% of the carbon footprint compared to a cable with a copper wire shield that complies with EU ESG guidelines and requirements (e.g., Directive (EU) 2022 / 2464).

[0010] It is particularly advantageous if the copolymer thickness is 0.05 mm or if a copolymer thickness of 0.05 mm is chosen. This allows for an ideal balance between flexibility and bonding with the aluminum strip.

[0011] Furthermore, it is advantageous if the HDPE sheath has a Shore hardness of 51 ± 1 Shore D 15 seconds. The Shore hardness is measured according to ASTM D2240(15 see). It has been found that this high hardness is surprisingly suitable, as it still allows sufficient flexibility for bending while providing good protection for the aluminum strip.

[0012] Furthermore, it is advantageous if the HDPE sheath is flame-retardant or self-extinguishing. This enables particularly robust and safe cabling and prevents the spread of fire. Flame-retardant or self-extinguishing preferably refers to classification Eca or Fea according to Regulation (EU) 2016 / 364.

[0013] It can be advantageous if the aluminum tape, coated on one side with a copolymer, bonds the tape overlap and itself to the HDPE sheath, acting as shielding, return conductor, and transverse and outer longitudinal barrier against moisture. In this way, the aluminum tape can fulfill multiple functions, simplifying the cable construction.

[0014] It is particularly advantageous if the aluminum strip is selected such that its one-second short-circuit current is at least as high as that of a copper wire cable of the same cross-section. This can be achieved, for example, by selecting a suitable thickness for the aluminum strip. This results in a particularly high electrical current-carrying capacity for the aluminum strip.

[0015] The copolymer-free aluminum tape simultaneously serves as cable shielding, cable return conductor, and transverse moisture barrier, making the cable waterproof in both the transverse and longitudinal directions. Furthermore, a very small bending radius of up to 11 x D is achieved, where D is the outer diameter of the cable.

[0016] The aluminum tape is coated on one side with a copolymer that bonds the tape overlap and itself to the outer sheath of the HDPE cable, thus acting as shielding, return conductor and moisture barrier in both transverse and longitudinal directions.

[0017] Thanks to the use of aluminum tape in the cable's construction, the successive layers adhere precisely to one another, resulting in better and faster heat transfer from the cable's interior to the exterior. Consequently, this leads to a lower operating temperature for both the working conductor and the aluminum tape return conductor. Furthermore, by selecting an appropriate aluminum tape thickness, a short-circuit current rating (i.e., a one-second short-circuit current in kA / s) through the aluminum tape can be achieved, comparable to that of a copper wire return conductor of the same cross-section. This allows for a smaller cable diameter, a smaller bending radius, and a significantly reduced cable weight.

[0018] The invention is illustrated in a schematic drawing using an exemplary embodiment. The drawing shows:

[0019] Fig. 1 shows the finished cable in a perspective view; and

[0020] Fig. 2 shows the individual elements of the single-core cable produced according to the invention.

[0021] The process for manufacturing the single-core cable 1 comprises simultaneously extruding the conductor shield 2, the insulation 3, and the insulating shield 4 as three layers in a single operation. Following this, the semiconducting intuitive tape 5 is laid longitudinally with an overlap, or optionally spirally with an overlap, onto the insulating shield 4. A copolymer-coated aluminum tape 6, with a thickness of at least 0.3 mm, is laid longitudinally with an overlap and bonded with an ethylene copolymer 7. Finally, the outer layer 8 is extruded from HDPE. The aluminum tape 6 is coated on one side with a copolymer, so that the tape overlap bonds with the sheathing, i.e., the HDPE sheath, and serves as a shield, return conductor, and moisture barrier in both the transverse and longitudinal directions.

[0022] Thanks to the use of aluminum tape in the cable construction, the successive layers adhere precisely to one another, resulting in better heat transfer from the inside of the cable to the outside and consequently a lower operating temperature for both the working conductor and the tape return conductor. This also removes air from the cable's interior during the manufacturing process, which reduces the need for cooling during normal operation. Furthermore, by selecting the appropriate thickness and width of the aluminum tape, the same short-circuit current rating can be achieved as with a copper wire return conductor of the same cross-section. In addition, compared to cables with a copper wire shield, a significantly higher (approximately...)

[0023] 5% to 15%) long-term current carrying capacity of the cable's working conductor is achieved.

Claims

PATENT CLAIMS 1. A method for producing a single-core cable, wherein a conductor shield (2), an insulation (3) and an insulating shield (4) are simultaneously extruded as three layers in a single operation, after which a semiconducting intumescent tape (5) is laid longitudinally with an overlap or spirally with an overlap onto the insulating shield (4), while a copolymer-coated aluminum tape (6) with a thickness of at least 0.30 mm is laid longitudinally with an overlap, followed by extrusion of the HDPE sheath (8), wherein the thickness of the copolymer is between 0.04 mm and 0.06 mm.

2. The method according to claim 1, characterized in that the thickness of the copolymer is 0.05 mm.

3. Method according to claim 1 or 2, characterized in that the HDPE shell has a Shore hardness of 51 ± 1 Shore D 15 s.

4. Method according to one of claims 1 to 3, characterized in that the HDPE casing is flame-retardant or self-extinguishing.

5. Method according to one of claims 1 to 4, characterized in that the aluminium strip (6), which is coated on one side with a copolymer that bonds the strip overlap and itself to the HDPE sheath (8), is designed as a shield, as a return conductor and as a transverse and outer longitudinal barrier against moisture.

6. Method according to one of claims 1 to 5, characterized in that the aluminium strip (6) is selected such that the one-second short-circuit current of the aluminium strip (6) is at least as high as the one-second short-circuit current of a cable made of copper wires of the same cross-section. 2026 04 17 MT / IV

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