A production line and a production method for non-crosslinked medium and high voltage power cable insulation

Abstract

The application discloses a production line for non-cross-linked material high-voltage power cable insulation, which comprises a wire storage device, a traction machine, an extruder, a non-cross-linked cooling device, a gas-liquid separator, a water cooling device and a wire collecting device arranged in sequence, and an electromagnetic heating device is further arranged between the water cooling devices, the electromagnetic heating device comprises a heat preservation layer with a through hole, the cable can pass through the through hole, and a heating coil is wound outside the heat preservation layer. The application solves the technical problem of developing a production line and a production method for non-cross-linked material high-voltage power cable insulation, which can avoid the generation of micropores and internal stress of the insulation.

Description

Technical Field

[0001] This invention relates to the field of cable manufacturing technology, and in particular to a production line and method for high-voltage power cable insulation using non-crosslinked materials. Background Technology

[0002] Currently, the demand for power cables is increasing rapidly, and the application scope of cables is also gradually expanding. For aesthetic reasons and to save urban land resources, overhead power transmission lines and communication lines are gradually disappearing from view. However, most medium and high voltage cables widely used domestically and internationally now use cross-linked polyethylene materials, with their semi-conductive outer shielding material being cross-linked polyethylene material with added carbon black. It is well known that cross-linked polyethylene materials are not easily recycled or reused, both during processing and after reaching their service life, which is detrimental to the environment. Therefore, non-cross-linked medium and high voltage cable materials have become a research hotspot. Significant progress has been made in the production methods of non-cross-linked medium and high voltage insulation materials, represented by vinyl ester and polypropylene insulation materials. However, the insulation production process for non-cross-linked medium and high voltage cables is still under exploration. Because the extrusion temperature of cross-linked polyethylene cables is around 120℃, while that of non-cross-linked cable materials is around 170℃, if the extruded material is immediately cooled in water below 100℃, it can easily lead to micropores in the insulation, internal stress, and even water ingress. Therefore, cooling methods and stress relief for the insulation of non-crosslinked medium and high voltage cables are problems that need to be solved.

[0003] Therefore, those skilled in the art are dedicated to developing a production line and method for high-voltage power cable insulation in non-crosslinked materials that can avoid micropores and internal stress in the insulation. Summary of the Invention

[0004] In view of the above-mentioned deficiencies of the prior art, the present invention discloses a production line and production method for high-voltage power cable insulation in non-crosslinked materials. The technical problem to be solved is to provide a production line and production method for high-voltage power cable insulation in non-crosslinked materials that can avoid the generation of micropores and internal stress in the insulation.

[0005] To achieve the above objectives, the present invention provides a production line for high-voltage power cable insulation in non-crosslinked materials, comprising a wire storage device, an upper traction machine, an extruder, a non-crosslinked cooling device, a gas-liquid separator, a water cooling device, and a take-up device arranged in sequence. An electromagnetic heating device is also provided between the water cooling devices. The electromagnetic heating device includes an insulation layer with a through hole inside, through which an insulated cable can pass. A heating coil is wound around the outside of the insulation layer.

[0006] Preferably, the take-up device includes a reel and a take-up disc.

[0007] Preferably, the water-cooling device is a water-cooling pipe, which includes a shaping cooling zone and a secondary cooling zone, with the electromagnetic heating device located between the shaping cooling zone and the cooling zone. This allows the water-cooling pipe to perform initial shaping cooling and secondary cooling on the cable until it is cooled to room temperature, while the electromagnetic heating device is used to relieve stress on the insulation.

[0008] Preferably, a plurality of non-crosslinking cooling devices are provided between the extruder and the gas-liquid separator. Each non-crosslinking cooling device includes an air inlet pipe and an air extraction pipe that are connected to the insulation. The air inlet pipe has two air inlet channels corresponding to the insulation. The air inlet pipes of the plurality of non-crosslinking cooling devices are supplied with nitrogen by the main air inlet pipe, and the air extraction pipes of the plurality of non-crosslinking cooling devices are exhausted by the main air extraction pipe.

[0009] This invention also provides a production line and method for producing high-voltage power cable insulation using non-crosslinked materials. The production line for high-voltage power cable insulation using non-crosslinked materials as described above includes the following steps:

[0010] 1) The conductor on the cable storage device passes through the upper traction machine and enters the extruder. The extruder head extrudes the conductor at a temperature of 165-175°C to form an insulated cable.

[0011] 2) Low-temperature nitrogen gas with a pressure of 1.0-1.5 MPa, a purity of not less than 99.5%, and a temperature of 80-90°C is introduced into the non-crosslinking cooling device for non-crosslinking cooling, so that the temperature of the insulation is reduced to 85-95°C;

[0012] 3) After the cable has undergone non-crosslinking cooling, it is separated into gas and liquid by a gas-liquid separator, and then the insulation is cooled in the shaping cooling zone of the water-cooled pipe. After the shaping cooling, the temperature of the insulation is reduced to 45-55℃.

[0013] 4) After the cable has been shaped and cooled, it enters the electromagnetic heating device to raise the temperature of the insulation to 100-110°C for post-stress relief, and then enters the cooling zone of the water cooling pipe to cool to room temperature.

[0014] 5) The cable, cooled to room temperature, is passed through the reel and then wound up by the take-up reel.

[0015] Preferably, in the non-crosslinking cooling, cryogenic nitrogen is introduced from the bottom of both sides of the insulation and nitrogen is extracted from the top of the insulation under pressure.

[0016] The beneficial effects of this invention are:

[0017] Based on the existing production line and process for cross-linked polyethylene insulation, after the extruder completes the three-layer co-extrusion, the original heating pipes no longer require nitrogen pressurization heating; instead, cooling is performed directly, improving production efficiency and reducing production costs. Because non-cross-linked cable insulation materials are not cross-linked internally, they need immediate cooling and shaping after extrusion; otherwise, the cable's outer diameter and eccentricity will change significantly. This invention replaces the high-temperature, high-pressure nitrogen used in the original cross-linked insulation with low-temperature nitrogen. A non-cross-linked cooling device and a water-cooling device are used for step-by-step cooling, first lowering the insulation temperature to approximately 90°C before direct water cooling for shaping, avoiding problems such as micropores, internal stress, water ingress, and even breakdown. Furthermore, by introducing the cable into an electromagnetic heating device, the conductor of the cable is heated by an induced current generated through a changing magnetic field, reaching the temperature at which polymer crystallization melts, thus eliminating internal stress. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of a production line for high-voltage power cable insulation using the non-crosslinked material of this invention;

[0019] Figure 2 This is a schematic diagram of the electromagnetic heating device of the present invention;

[0020] Figure 3 This is a front view schematic diagram of the non-crosslinking cooling device of the present invention;

[0021] Figure 4 This is a left-side schematic diagram of the non-crosslinking cooling device of the present invention.

[0022] In the above attached figures: 1. Cable storage device; 2. Upper traction machine; 3. Extruder; 4. Non-crosslinking cooling device; 41. Air inlet pipe; 42. Air extraction pipe; 5. Gas-liquid separator; 6. Water cooling device; 71. Wheel; 72. Take-up reel; 8. Cable; 81. Insulation; 82. Conductor; 9. Electromagnetic heating device; 91. Insulation layer; 92. Heating coil. Detailed Implementation

[0023] The present invention will be further described below with reference to the accompanying drawings and embodiments. It should be noted that in the description of the present invention, terms such as "upper," "lower," "left," "right," "inner," and "outer" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These terms are used only for the convenience of describing the present invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific manner. Therefore, they should not be construed as limitations on the present invention. Terms such as "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0024] like Figure 1As shown, this invention provides a production line for high-voltage power cable insulation using non-crosslinked materials, comprising a wire storage device 1, an upper traction machine 2, an extruder 3, a non-crosslinked cooling device 4, a gas-liquid separator 5, a water cooling device 6, and a take-up device arranged sequentially. The take-up device includes a wheel 71 and a take-up reel 72, and an electromagnetic heating device 9 is also provided between the water cooling device 6. Figure 2 As shown, the electromagnetic heating device 9 includes an insulation layer 91 with internal through holes through which a cable 8 covered with insulation 81 can pass. A heating coil 92 is wound around the insulation layer 91. Furthermore, the water cooling device 6 is a water cooling pipe, which includes a shaping cooling zone and a secondary cooling zone. The electromagnetic heating device 9 is located between the shaping cooling zone and the cooling zone, allowing the water cooling pipe to perform initial shaping cooling and secondary cooling on the cable 8 until it is cooled to room temperature. The electromagnetic heating device 9 is used to relieve stress on the insulation 81. Further, several non-crosslinking cooling devices 4 are provided between the extruder 3 and the gas-liquid separator 5. Each non-crosslinking cooling device 4 includes an inlet pipe 41 and an exhaust pipe 42 that are connected to the insulation 81. The inlet pipe 41 has two inlet channels corresponding to the insulation 81. The inlet pipes 41 of the several non-crosslinking cooling devices 4 are supplied with nitrogen from the main inlet pipe, and the exhaust pipes 42 of the several non-crosslinking cooling devices 4 are exhausted from the main exhaust pipe.

[0025] This invention also provides a method for producing high-voltage power cable insulation using non-crosslinked materials, the production line for high-voltage power cable insulation using non-crosslinked materials described above, comprising the following steps:

[0026] 1) The conductor 82 on the wire storage device 1 passes through the upper traction machine 2 and enters the extruder 3. The extruder 3 extrudes the conductor 82 at a temperature of 165-175°C to form a cable 8 with insulation 81.

[0027] 2) Low-temperature nitrogen gas with a pressure of 1.0-1.5 MPa, a purity of not less than 99.5%, and a temperature of 80-90°C is introduced into the non-crosslinking cooling device 4 for non-crosslinking cooling, so that the temperature of the insulation 81 is reduced to 85-95°C;

[0028] 3) After the cable 8 has undergone non-crosslinking cooling, it passes through the gas-liquid separator 5 to separate the gas and liquid, and then passes through the shaping cooling zone of the water cooling pipe to shape and cool the insulation 81. After shaping and cooling, the temperature of the insulation 81 is reduced to 45-55℃.

[0029] 4) The cable 8, after being shaped and cooled, enters the electromagnetic heating device 9 to raise the temperature of the insulation 81 to 100-110°C for post-stress relief, and then enters the cooling zone of the water cooling pipe to cool to room temperature.

[0030] 5) The cable 8, cooled to room temperature, is wound up by the take-up reel 72 after passing through the reel 71.

[0031] In addition, in non-crosslinking cooling, the cooling efficiency and effect are improved by introducing low-temperature nitrogen gas from the bottom sides of the insulation 81 and extracting nitrogen gas from the top of the insulation 81 under pressure, and then supplying gas through the bottom sides.

[0032] In the above embodiments, based on the existing production line and process for cross-linked polyethylene insulation, after the extruder completes the three-layer co-extrusion, the original heating pipes no longer require nitrogen pressurization heating and can be directly cooled, improving production efficiency and reducing production costs. Because the non-cross-linked cable insulation material is not cross-linked internally, it needs to be cooled and shaped immediately after extrusion; otherwise, the outer diameter and eccentricity of the cable 8 will change significantly. This invention uses low-temperature nitrogen to replace the high-temperature, high-pressure nitrogen used in the original cross-linked insulation. A non-cross-linked cooling device 4 and a water-cooling device 6 are used for step-by-step cooling, first lowering the temperature of the insulation 81 to approximately 90°C before directly using water cooling to cool and shape the insulation 81, avoiding problems such as micropores, internal stress, water ingress, and even breakdown in the insulation 81. On the other hand, by introducing the cable 8 into the electromagnetic heating device 9, the conductor 82 of the cable 8 is heated by an induced current generated by a changing magnetic field, reaching the temperature at which polymer crystallization melts, thereby eliminating internal stress.

[0033] In practice, the existing production line MV-CCV-LINE 62111-00 from the international cable equipment manufacturer TEOESTER can be used. After improving nitrogen cooling and post-stress relief, the existing production line for producing cross-linked polyethylene insulation can be converted into a production line for producing high-voltage power cable insulation using non-cross-linked materials.

[0034] This patent focuses on medium- and high-voltage non-crosslinked insulated cables, whose internal stress is mainly introduced by the cable manufacturing process. The post-stress relief achieved through electromagnetic heating during cable manufacturing allows for a more thorough release of internal stress.

[0035] Currently, X-ray diffraction (XRD) is the most commonly used method for polymer stress analysis. XRD utilizes the high-speed electrons bombarding atoms, causing them to transition and generating rays, which are then used to study the internal structure of materials. Related literature indicates that XRD can qualitatively analyze the type and magnitude of internal stress in materials. By heat-treating the material to release internal stress, the change in interplanar spacing (d) before and after stress release (Δd) can be calculated; a larger absolute value of Δd corresponds to a larger residual stress.

[0036] The process parameters of the test samples are shown in the table below:

[0037]

[0038] Multiple XRD measurements were performed on each test sample to analyze changes in crystal planes and interplanar spacing, thereby determining the differences in internal stress within the XLPE cable insulation. The average value was then taken to ensure the reliability of the results. Jade5 XRD was used for analysis to calculate the interplanar spacing values, and the interplanar spacing at different positions and directions before and after degassing of the three peaks was compared, as shown in the table below:

[0039]

[0040] The table shows that under the same conditions, the interplanar spacing value is slightly larger when the electromagnetic heating device is off than when it is on. Turning on the electromagnetic heating device reduces the interplanar spacing value d for both 100 and 200 to some extent, indicating a reduction in internal insulation stress. The electromagnetic heating device clearly achieves the effect of post-stress relief.

[0041] The preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. A production line for high-voltage power cable insulation using non-crosslinked materials, characterized in that: The device includes a wire storage device (1), an upper traction machine (2), an extruder (3), a non-crosslinking cooling device (4), a gas-liquid separator (5), a water cooling device (6), and a take-up device arranged in sequence. An electromagnetic heating device (9) is also provided between the water cooling devices (6). The electromagnetic heating device (9) includes a heat insulation layer (91) with a through hole inside, through which a cable (8) can pass. A heating coil (92) is wound around the heat insulation layer (91). Several non-crosslinking cooling devices (4) are provided between the extruder (3) and the gas-liquid separator (5). Each non-crosslinking cooling device (4) includes an air inlet pipe (41) and an air extraction pipe (42) that are connected to the insulating layer (81). The air inlet pipe (41) has two air inlet channels corresponding to the insulating layer (81). The air inlet pipes (41) of several non-crosslinking cooling devices (4) are supplied with nitrogen by the main air inlet pipe, and the air extraction pipes (42) of several non-crosslinking cooling devices (4) are exhausted by the main air extraction pipe. By sending low-temperature nitrogen into the bottom of both sides of the insulating layer (81) and extracting nitrogen from the top of the insulating layer (81) under pressure, the temperature of the insulating layer (81) is reduced to 85-95°C. The water cooling device (6) is a water cooling pipe, which includes a shaping cooling zone and a cooling zone, and the electromagnetic heating device (9) is located between the shaping cooling zone and the cooling zone.

2. The production line for high-voltage power cable insulation in non-crosslinked materials as described in claim 1, characterized in that: The take-up device includes a reel (71) and a take-up reel (72).

3. A method for producing high-voltage power cable insulation in non-crosslinked materials, using the production line for high-voltage power cable insulation in non-crosslinked materials as described in claim 2, characterized in that, Includes the following steps: 1) The conductor (82) on the wire storage device (1) passes through the upper traction machine (2) and enters the extruder (3). The extruder (3) extrudes the conductor (82) at a temperature of 165-175°C to form a cable (8) with an insulation layer (81). 2) Low-temperature nitrogen gas with a pressure of 1.0 to 1.5 MPa, a purity of not less than 99.5%, and a temperature of 80 to 90°C is introduced into the non-crosslinking cooling device (4) for non-crosslinking cooling, so that the temperature of the insulation layer (81) is reduced to 85 to 95°C; 3) After the cable (8) has undergone non-crosslinking cooling, the gas and liquid are separated by the gas-liquid separator (5), and then the insulation layer (81) is cooled by the water cooling pipe. After the insulation layer (81) is cooled, the temperature is reduced to 45-55℃. 4) The cable (8) after being shaped and cooled is put into the electromagnetic heating device (9) to raise the temperature of the insulation layer (81) to 100-110°C for post-stress relief, and then it is cooled to room temperature by water cooling pipe. 5) The cable (8) cooled to room temperature is wound up by the take-up reel (72) after passing through the reel (71).

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