Joint method in insulation extrusion process of medium-voltage cable

Abstract

A joint method in an insulation extrusion process of a medium-voltage cable relates to the technical field of cable processing, and comprises the following steps: carrying out crimping on the premise of reserving a single wire on the outer layer part of a conductor, and carrying out differentiation treatment on the joint of the inner layer and the outer layer of the two conductors. Compared with a mode of completely stripping the outer layer single wires in the prior art, the reserved outer layer single wires can obviously improve the tensile strength of the joint. Meanwhile, according to the stress characteristics of different conductors, differentiation treatment is carried out, the first conical surface and the second conical surface can achieve smooth transition of the inner layer and the outer layer, and the situation that stress changes abruptly when the machine head is penetrated is avoided. However, as a forward head side, the cross section of the outer layer single wire is blocked in the forward direction when the single wire passes through the machine head, so that the outer layer single wire is easy to upwarp, the overall strength and the coating effect of an insulating layer are influenced, and a smoother conical surface needs to be processed to ensure better trafficability. The joint method is simple and convenient to operate, can effectively improve the mechanical strength of the joint, prevents the conductor wire core from being snapped, and has a better application value.

Description

Technical Field

[0001] This invention relates to the field of cable manufacturing technology, and more specifically, to a jointing method in the extrusion process of medium-voltage cable insulation. Background Technology

[0002] With the current development demand of the large-scale infrastructure market and the promotion and application of aluminum or aluminum alloy power cables in the new energy market, 35kV and below aluminum (aluminum alloy) cables have become an indispensable part. However, in medium-voltage cross-linked cables, small-section aluminum (aluminum alloy) cross-linked cables with 120mm insulation are still in use. 2 (25~120) During the extrusion process, joint control presents significant production challenges. Different companies use different jointing methods for aluminum (aluminum alloy) conductors during insulation extrusion, including conductor welding, crimping, or direct hook connection. The most effective method is auxiliary sleeve crimping. However, due to uneven tension control and significant differences in conductor strength during insulation extrusion, intermediate conductor joints become a problem. Using existing crimping methods for intermediate joints, due to differences in material strength, regardless of whether "straight pipe" or "water-blocking pipe" crimping is used, the conductor core is easily broken due to tension mismatch and sag fluctuations, leading to significant material loss and waste after equipment downtime. Summary of the Invention

[0003] The purpose of this invention is to provide a jointing method in the extrusion process of medium-voltage cable insulation, which is simple and convenient to operate, can effectively improve the mechanical strength at the joint, and prevent the conductor core from breaking.

[0004] The embodiment of the present invention is achieved as follows: A jointing method during the extrusion process of medium-voltage cable insulation, comprising: S1. Take the two conductors to be connected, and partially remove the outer layer of single wires at their joints, retaining 30% to 50% of the outer layer of single wires; S2. Insert the two processed conductors into both ends of the connector tube and crimp them together; S3. Polish the two conductors separately so that the conductor on the gun head side forms a first conical surface with an angle of 50~60° at the junction of the outer and inner layers, and the conductor on the straight head side forms a second conical surface with an angle of 20~30° at the junction of the outer and inner layers.

[0005] The beneficial effects of the embodiments of the present invention are: This invention provides a jointing method during the extrusion process of medium-voltage cable insulation. The method involves crimping while retaining the outer layer of individual wires, and differentiated treatment at the junction of the inner and outer layers of the two conductors. Compared to the prior art method of completely stripping the outer layer of individual wires, retaining the outer layer significantly improves the tensile strength at the joint. Simultaneously, differentiated treatment is applied based on the different stress characteristics of the conductors; both the first and second conical surfaces achieve a smooth transition between the inner and outer layers, avoiding abrupt stress changes when passing through the extrusion head. However, on the straight side, the cross-section of the outer layer of individual wires is obstructed when passing through the extrusion head, causing the outer layer of individual wires to easily warp, affecting the overall strength and the insulation layer's coverage effect. Therefore, a more gently sloping conical surface needs to be formed to ensure better passage. This jointing method is simple and convenient to operate, effectively improves the mechanical strength at the joint, prevents conductor core breakage, and has significant application value. Attached Figure Description

[0006] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.

[0007] Figure 1 This is a schematic diagram of the crimping process of a jointing method in the extrusion process of medium-voltage cable insulation provided in an embodiment of the present invention. Figure 2 This is a schematic diagram of the grinding process of a joint in the extrusion process of medium-voltage cable insulation provided in an embodiment of the present invention. Figure 3 This is a test result diagram of the joint after joint treatment in the extrusion process of medium voltage cable insulation provided in Embodiment 2 of the present invention, in a tensile test. Figure 4 This is a test result diagram of the joint after treatment by the joint method in the medium-voltage cable insulation extrusion process provided in Comparative Example 2 of the present invention in a tensile test.

[0008] Icons: 100 - Connector tube; 200 - Conductor; 300 - Crimping die. Detailed Implementation

[0009] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to represent selected embodiments of the invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0010] A jointing method during the extrusion process of medium-voltage cable insulation, comprising: S1. Take the two conductors to be connected, and partially remove the outer layer of single wires at their joints, retaining 30% to 50% of the outer layer of single wires; S2. Insert the two processed conductors into both ends of the connector tube and crimp them together; S3. Polish the two conductors separately so that the conductor on the gun head side forms a first conical surface with an angle of 50~60° at the junction of the outer and inner layers, and the conductor on the straight head side forms a second conical surface with an angle of 20~30° at the junction of the outer and inner layers.

[0011] Compared to existing technologies that completely strip the outer single wire, retaining the outer single wire significantly improves the tensile strength at the joint. Furthermore, differentiated processing is applied based on the stress characteristics of different conductors; both the first and second conical surfaces achieve a smooth transition between the inner and outer layers, avoiding abrupt stress changes when passing through the head. However, on the guide side, the cross-section of the outer single wire is obstructed when passing through the head, causing it to easily warp, affecting overall strength and the insulation layer's coverage. Therefore, a smoother conical surface needs to be formed to ensure better passage. On the gun head side, the grinding distance is minimized to better maintain the integrity and strength of the outer single wire.

[0012] It should be noted that the angle between the first and second conical surfaces refers to the angle formed by them and the conductor axis. The smaller the angle, the smoother the transition. Furthermore, the length of the first conical surface along the conductor axis is 0.5~0.8cm; the length of the second conical surface along the conductor axis is 2.5~3cm. The first and second conical surfaces should be smooth and rounded. After polishing, polyester tape can be used to wrap the first and second conical surfaces. When wrapping, wrap an additional 5~10cm forward of the first conical surface and an additional 15~30cm backward of the second conical surface, for a total of 2~3 layers. Wrapping improves the smoothness of the transition and allows the inner and outer layers to adhere better, increasing the wiring strength.

[0013] Furthermore, in step S1, the number of outer layer single wires retained is 3 to 5. The retained outer layer single wires are distributed at intervals on the outer ring of the conductor. For example, if 4 wires are retained, one single wire can be retained every 90 degrees, which improves the balance of force in all directions.

[0014] In step S2, during crimping, the joint tube is crimped sequentially from the center outwards to both ends, with each crimping point being crimped 3-5 times. Between two crimps, the joint tube is rotated 50-70°. Preferably, each crimping point is crimped 3 times, with the joint tube rotating 60° between two crimps. This crimping method ensures a tighter crimp and avoids excessive compression at the same location.

[0015] Furthermore, in step S3, the first and second conical surfaces are 1.5-2 cm away from the edge of the connector tube. This distance should not be too large, as this would require stripping a longer outer single-layer wire, leading to a reduction in overall strength. The distance should also not be too small, as this would affect the machining of the first and second conical surfaces, potentially causing operational errors.

[0016] Optionally, during the process of the connector tube passing through the die head of the insulation extruder, the conductor rotation speed can be reduced and the extrusion thickness of the insulation layer can be increased. Reducing the conductor rotation speed can decrease the torque at the joint, preventing the connector tube and conductor from loosening and better ensuring the wiring strength. Increasing the insulation thickness can, on the one hand, offset the thickness change caused by stripping the outer single wire, and on the other hand, strengthen the joint strength through a thicker insulation layer.

[0017] Specifically, when the connector tube reaches 30-40m before entering the machine head, the conductor's rotation speed is reduced to 15-30° for every 1.5m the conductor moves forward; this is a reduction of approximately 33.3%-50% compared to the normal rotation speed. The normal rotation speed is then restored 70-110m after the connector tube passes the machine head.

[0018] When the connector tube reaches 30-40m before entering the die head, increase the extrusion thickness of the insulation layer by 5%-10%; after the connector tube passes through the die head, return to the normal extrusion thickness. Under the above process parameters, the strength performance at the joint is better.

[0019] Furthermore, by monitoring for nitrogen leakage at the die head inlet, it can be determined whether the connector pipe passes through the die head. Alternatively, it can be determined by observing parameters such as current, voltage, and extrusion thickness.

[0020] Furthermore, the cross-sectional area of ​​the conductor is ≤150mm². 2 For conductors with small cross-sections like this, breakage is more likely, making this method most effective. The connector can be a straight-through conduit or a water-blocking conduit. Because some of the outer single-layer wires are retained, the connector must be one size larger than the conductor to ensure sufficient space to accommodate the retained outer single-layer wires. For 185 mm... 2 For conductors of specifications of 1 and above, since they have good strength, the existing technology of removing all the outer single wires and then crimping them is sufficient. In this case, a connector tube of the same specification as the conductor should be selected to improve the tightness of the connection between the conductor and the connector tube.

[0021] The following specific examples will provide further details. Example 1

[0022] This embodiment provides a jointing method during the extrusion process of medium-voltage cable insulation, using 95mm... 2 Taking aluminum alloy cable as an example, the conductor of this model includes one center single wire, five inner single wires surrounding the center single wire, and ten outer single wires surrounding the inner single wires. The center single wire and the inner single wires can each withstand a tensile force of 403 N / wire, while the outer single wires can withstand a tensile force of 658.3 N / wire.

[0023] The joint method specifically includes: S1. Take the two conductors to be connected, remove part of the outer single wire at the joint, and keep 4 single wires in the outer layer. The 4 single wires are evenly distributed in the outer layer.

[0024] S2. Insert the two treated conductors into both ends of the connector tube and crimp them together; when crimping, refer to... Figure 1 As shown, the joint tube 100 is first crimped near the center using the crimping die 300 (top image), and then the outer part is crimped using the moving conductor 200 (middle image). Each crimping position is crimped three times, with the joint tube 100 rotating 60° between each crimping. After crimping, the surface of the joint tube 100 is polished until smooth and round.

[0025] S3. For example Figure 2As shown, the two conductors are polished to create a first conical surface with a 50° angle at the junction of the outer and inner layers on the conductor on the nozzle side, and a second conical surface with a 2° angle at the junction of the outer and inner layers on the conductor on the connector side. The first and second conical surfaces are 1.5cm from the edge of the connector tube. The length of the first conical surface along the conductor axis is 0.5~0.8cm; the length of the second conical surface along the conductor axis is 2.5~3cm. Both the first and second conical surfaces should be smooth and rounded. After polishing, polyester tape can be used to wrap the first and second conical surfaces. When wrapping, wrap an additional 5cm forward of the first conical surface and an additional 17.5cm backward of the second conical surface, for a total of 2~3 layers. Example 2

[0026] This embodiment provides a jointing method during the extrusion process of medium-voltage cable insulation, which, based on Embodiment 1, further enhances parameter control when the joint tube passes through the die head. Specifically, it includes: When the connector tube reaches 30-40m before entering the machine head, reduce the conductor's rotation speed to 15-30° for every 1.5m the conductor moves forward; this is a reduction of approximately 33.3%-50% compared to the normal rotation speed. Resume the normal rotation speed 70-110m after the connector tube passes the machine head.

[0027] When the connector tube reaches 30-40m before entering the die head, increase the extrusion thickness of the insulation layer by 5%-10%; after the connector tube passes through the die head, restore the normal extrusion thickness.

[0028] The rotation speed can be adjusted by adjusting the take-up and twisting mechanism. Whether it's a roller-type or track-type twisting mechanism, firstly, the clamping handwheel is turned clockwise to clamp and counter-clockwise to release. The angle adjustment is controlled by two sets of rollers, each with an adjustment handle controlling the roller height. The left roller at the wire inlet is higher than the right; counter-clockwise rotation is forward (aligned with the conductor twisting direction); the left roller is lower than the right; clockwise rotation is reverse (opposite to the conductor twisting direction).

[0029] After the wire twister is clamped, mark the insulation surface directly above the lower sealed outlet with tape and observe the rotation angle of the tape to the wire twister inlet. If the rotation angle is within 60°, simply tighten or loosen the clamping handwheel; if it exceeds 60°, you need to adjust the roller or the angle of the track inlet.

[0030] It is important to note that the wire twister should not be clamped too tightly, as this can lead to insulation deformation and the risk of insulation slippage. In such cases, the wire twister needs to be loosened, the wire inlet angle adjusted, and then tightened again. Adjusting the wire twister angle must be done according to the instructions from the server room, and the adjustment process must be communicated with the server room personnel in a timely manner. Server room personnel must constantly observe the suspension condition, and they must coordinate with each other when the wire twister is almost in the server room to avoid loosening the wire twister too early, which could lead to excessive eccentricity, or loosening it too late, which could cause excessive stress at the joint and break the conductor.

[0031] Comparative Example 1 This comparative example provides a jointing method in the insulation extrusion process of medium-voltage cables. Its operation is basically the same as that of Example 1, except that for both conductors, the outer single wire is completely stripped.

[0032] Comparative Example 2 This comparative example provides a jointing method in the insulation extrusion process of medium-voltage cables. Its operation is basically the same as that of Example 2, except that for both conductors, the outer single wire is completely stripped.

[0033] Comparative Example 3 This comparative example provides a jointing method in the extrusion process of medium-voltage cable insulation. Its operation is basically the same as that of Example 2, except that all the outer single wires are stripped from the conductor on the straight end side, while the conductor on the gun end side retains the outer 4 single wires.

[0034] Comparative Example 4 This comparative example provides a jointing method in the extrusion process of medium-voltage cable insulation. Its operation is basically the same as that of Example 2, except that the conductor on the straight end side retains the outer 4 single wires, while the conductor on the gun end side strips all the outer single wires.

[0035] Test example The joints were processed using the methods provided in Examples 1-2 and Comparative Examples 1-3, and strength tests were performed on the joints. The test results are shown in Table 1.

[0036] Table 1. Tensile strength test pull Test results Example 1 4500N Not broken Example 1 5000N Pulling Example 2 5000N Not broken Comparative Example 1 2500N Pulling Comparative Example 2 2500N Pulling Comparative Example 3 2500N Break along one side of the head Comparative Example 4 2500N The gun head broke off on one side. The test results show that the joint method of Embodiment 1 of this invention can withstand a tensile force of 4500N without breaking, while after the corresponding process adjustment in Embodiment 2, the tensile force resistance was even increased to 5000N (test results are shown in Figure 1). Figure 3 (As shown). In contrast, Comparative Example 1, processed using the traditional method of stripping all the outer single strands, experienced strand breakage under a tensile force of 2500N. Comparative Example 2, while implementing process control after stripping all the outer single strands, did not show a significant change in joint strength, and still experienced strand breakage under a tensile force of 2500N (test results are shown). Figure 4 (As shown). In Comparative Examples 3 and 4, the outer single-wire portion of the conductor on one side was retained, and the final strand breakage occurred on the side where the entire outer layer was removed.

[0037] In summary, this invention provides a jointing method for medium-voltage cable insulation extrusion, which includes crimping while retaining the outer layer of single wires, and differentiated treatment at the junction of the inner and outer layers of the two conductors. Compared to the prior art method of completely stripping the outer layer of single wires, retaining the outer layer of single wires can significantly improve the tensile strength at the joint. Simultaneously, differentiated treatment based on the stress characteristics of different conductors allows for a smooth transition between the inner and outer layers using both the first and second conical surfaces, avoiding abrupt stress changes when passing through the extrusion head. However, as the straight side, the cross-section of the outer layer of single wires is obstructed when passing through the extrusion head, causing the outer layer of single wires to easily warp, affecting the overall strength and the insulation layer's coverage effect. Therefore, a more gently sloping conical surface needs to be formed to ensure better passage. This jointing method is simple and convenient to operate, effectively improves the mechanical strength at the joint, prevents conductor core breakage, and has significant application value.

[0038] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A jointing method during the extrusion process of medium-voltage cable insulation, characterized in that, include: S1. Take the two conductors to be connected, and partially remove the outer layer of single wires at their joints, retaining 30% to 50% of the outer layer of single wires; S2. Insert the two processed conductors into both ends of the connector tube and crimp them together; S3. Polish the two conductors separately so that the conductor on the gun head side forms a first conical surface with an angle of 50~60° at the junction of the outer and inner layers, and the conductor on the straight head side forms a second conical surface with an angle of 20~30° at the junction of the outer and inner layers.

2. The joint method according to claim 1, characterized in that, In step S1, the number of outermost single lines is 3 to 5.

3. The joint method according to claim 1, characterized in that, In step S2, when crimping, the joint tube is crimped sequentially from the center to both ends, with each crimping position being crimped 3 to 5 times, and the joint tube being rotated 50 to 70 degrees between two crimping operations.

4. The joint method according to claim 1, characterized in that, In step S3, the first conical surface and the second conical surface are 1.5~2cm away from the edge of the connector tube.

5. The joint method according to claim 4, characterized in that, The length of the first conical surface along the conductor axis is 0.5~0.8cm; the length of the second conical surface along the conductor axis is 2.5~3cm.

6. The joint method according to claim 1, characterized in that, Also includes: During the process of the connector tube passing through the die head of the insulation extruder, the rotational speed of the conductor is reduced and the extrusion thickness of the insulation layer is increased.

7. The joint method according to claim 6, characterized in that, When the connector tube reaches 30-40m before entering the machine head, the rotation speed of the conductor is reduced to a rotation angle of 15-30° for every 1.5m the conductor moves forward; the normal rotation speed is restored 70-110m after the connector tube passes the machine head.

8. The joint method according to claim 7, characterized in that, When the connector tube reaches 30-40m before entering the die head, the extrusion thickness of the insulation layer is increased by 5%-10%; the normal extrusion thickness is restored 10-15m after the connector tube passes the die head.

9. The joint method according to claim 8, characterized in that, By monitoring whether nitrogen is leaking from the inlet of the machine head, it can be determined whether the connector pipe passes through the machine head.

10. The joint method according to claim 1, characterized in that, The cross-sectional area of ​​the conductor is ≤150mm². 2 .

Images