CN107994517B - Manufacturing method of fusion-connection type straight-through joint for 10 kV-35 kV cable process - Google Patents

Abstract

The invention relates to the technical field of cable connection, in particular to a method for manufacturing a 10kV to 35kV cable process welding type through joint.

Description

Manufacturing method of 10kV to 35kV cable technology fusion type straight-through joint

technical field

The invention relates to the technical field of cable connection, in particular to a method for manufacturing a 10kV to 35kV cable technology fusion-bonded straight-through joint.

Background technique

With the continuous advancement of my country's urbanization process, cable lines have a tendency to gradually replace high-voltage overhead lines. The length of each reel of the distribution network cable is generally about 600 meters, that is, a straight-through joint must be installed every corresponding distance on the cable line, which shows that the number is quite large, and the straight-through joint is often the weakest place in the cable line , so the quality of the straight-through joint is an important factor in determining whether the cable line can run safely.

Existing straight-through joints are mainly divided into the following three types: insulating tape wrapping type, heat-shrinkable type and cold-shrinkable prefabricated type, but the failure rate of the above-mentioned three types of straight-through joints is relatively high. At present, the vast majority of cables used in the domestic distribution network are three-core. Once a breakdown accident occurs at the cable straight-through joint, simple repairs cannot restore the insulation performance of the joint, and a new cable must be replaced as a joint. In addition, due to the dense arrangement of cables in the cable trench/well, if a joint on one cable breaks down and catches fire, other cables will be ignited, which will easily lead to major accidents.

There are two main factors that lead to the failure of the existing straight-through joints: (1) Since the main insulation of the cable and the stress cone of the joint are two media and there is an overlapping interface, its insulation performance depends on the stress cone itself made of ethylene-propylene rubber or silicone rubber. Hold the cable mains insulation tight to maintain it. During the operation of the cable, there is a certain degree of thermal expansion and contraction due to the change of the flowing current, and the expansion coefficient of the main insulation of the cable is different from that of the stress cone of the joint. Insulation creates gaps, which induce partial discharge until a breakdown accident occurs; (2) The environment in the cable trench/well is relatively humid, and the existing straight-through joints mainly rely on stress cones to disperse the electric field, while metal waterproof joints cannot be used for 10kV to 35kV cables. Wrap waterproof tape for waterproofing. The waterproof performance of the waterproof tape will gradually decrease during use. Over time, water vapor will enter the gap between the main insulation of the cable and the stress cone, causing cable joint failure.

Contents of the invention

In order to solve the problems existing in the prior art, the present invention proposes a method for manufacturing a 10kV to 35kV cable technology fusion-type straight-through joint, through which the cable straight-through joint with excellent insulation strength and waterproofness can be quickly produced at the construction site.

The manufacturing method of the 10kV to 35kV cable process fusion type straight-through joint of the present invention comprises the following steps:

1) Cutting and stripping of the outer layer of the cable: saw two fractures in the radial direction at the butt ends of the two cables, and peel off the outer sheath, steel armor layer, Inner sheath and cut off the exposed padding.

2) Cutting, stripping and finishing of the core cable: peel off the copper shielding layer, outer semi-conductive layer, insulating layer and inner semi-conductive layer layer by layer from the core cable in the cable, and remove the outer semi-conductive layer. The end of the insulating layer and the inner semi-conductive layer is cut into a smooth transitional slope and polished smooth with a 600-mesh abrasive belt. Remove the insulation residue on the surface of the exposed inner semi-conductive layer with a mesh belt and polish the surface, then wrap the exposed outer semi-conductive layer, insulating layer and inner semi-conductive layer with polytetrafluoroethylene tape in the opposite direction for heat insulation protection ; Use a 240-mesh abrasive belt to remove the exposed core surface and the oxide layer at the fracture, and wrap and seal it with tape.

3) Presetting of pipe materials: put two heat shrinkable tubes on the cable, and put a silicone rubber dustproof cover on each of the three core cables inside the cable.

4) Welding of the wire core: Remove the tape outside the wire core, straighten the wire core and heat and dehumidify it, insert it into the welding mold to fix it, fill the welding mold with metal powder of the same material as the wire core for exothermic welding, and then put Grind the welding place to the same diameter as the original cable core.

5) Tape wrapping: Remove the high-temperature-resistant tape wrapped around the outer semiconductive layer, insulating layer and inner semiconductive layer, and use the same tape as the inner semiconductive layer to tightly wrap the core surface and the original inner The surface of the semi-conductive layer is higher than the inner semi-conductive layer of the original core cable within 1mm, and the two ends cover the slope-shaped end of the original inner semi-conductive layer; the inner semi-conductive repair layer is tightly wrapped with the same tape as the insulating layer. The semi-conductive repair layer, the original inner semi-conductive layer and the original insulating layer form an insulating repair layer whose surface is 5-8mm higher than the original insulating layer and whose two ends transition smoothly with the original insulating layer. The two ends of the insulating repair layer cover the original insulating layer The end of the pencil head of the layer; use the same material as the outer semi-conductive layer to tightly wrap the insulating repair layer, the original insulating layer and the surface of the original outer semi-conductive layer to form an outer semi-conductive repair with the same thickness as the original outer semi-conductive layer layer, the two ends of the outer semiconductive repair layer cover the slope-shaped end of the original outer semiconductive layer.

6) Fusion recovery of the inner semiconductive layer, insulating layer and outer semiconductive layer: move the silicone rubber dust cover to the outer semiconductive repair layer, completely cover and tightly wrap the outer semiconductive repair layer, Wrap a layer of aluminum foil on the outside of the sleeve and wrap it with imide tape to fix it, then lock and fix it with a plastic mold, and then heat it in a heating cylinder to fuse the strips that form the outer semi-conductive repair layer, insulating repair layer and inner semi-conductive layer , using high-frequency induction heating device to heat the core cable section near the two ends of the heating cylinder to make the outer semi-conductive repair layer and the original outer semi-conductive layer, the insulation repair layer and the original repair layer, the inner semi-conductive repair layer and the original inner semi-conductive layer to fuse Integral, the pressure in the shaping mold should not be lower than 1.8MPa when the heating is finished.

7) Restoration of the copper shielding layer: Remove the heating cylinder, plastic mold, imide tape, aluminum foil and silicone rubber dust cover, wrap and connect the original copper shielding layer on each core cable with copper mesh and apply a constant force The two ends of the copper mesh are fixed by springs, and then the three core cables are wrapped and bundled together with insulating tape.

8) Restoration of the inner sheath: Wrap the outer side of the insulating tape with waterproof tape and connect the original inner sheath of the two cables. When wrapping, the waterproof tape needs to be 100% stretched and half-lapped and wound for multiple layers, and then the The waterproof glue is evenly applied on the surface of the waterproof tape and covered with a heat-shrinkable tube, and the heat-shrinkable tube is evenly heated to make it fully shrink, and the two ends of the heat-shrinkable tube are wrapped with waterproof tape.

9) Connection of the steel armor layer: Use a 240-mesh abrasive belt to grind off the anti-rust paint on the surface of the original steel armor layer at the connection end of the two cables, and then wrap the heat-shrinkable copper braid with the two ends overlapping the original cable steel armor layer. The two ends of the braided copper braid are fixed with constant force springs, and finally the two constant force springs are wrapped and fixed with insulating tape.

10) Restoration of the outer sheath: use a 600-mesh abrasive belt to polish the surface of the original outer sheath at the connection end of the two cables and wrap the filling tape, then wrap the connected steel armor layer and the two cables with waterproof tape. Fill the original outer sheath of the tape. When wrapping, the waterproof tape needs to be stretched 100% and half-lapped to wrap multiple layers, and then the waterproof glue is evenly applied to the surface of the waterproof tape, and another heat-shrinkable tube is covered, evenly Heat the heat-shrinkable tube to make it fully shrink and wrap the two ends of the heat-shrinkable tube with waterproof tape, and finally wrap multiple layers of armored tape on the surface of the heat-shrinkable tube.

The heating process of the heating cylinder in the step 6) is: uniformly increase the temperature for 20-30 minutes to 100°C and keep the temperature for 5-10 minutes, then slowly increase the temperature for 15-25 minutes to 185°C and keep the temperature for 40-50 minutes, after the heating cylinder is heated to above 100°C Turn on the high-frequency induction heating device to output 350A induction heating current at 380V voltage to simultaneously heat the core cable sections near both ends of the heating cylinder.

Wrapping with PTFE tape can effectively block the heat radiated from the welding point to protect the core cable, and it is not easy to adhere to the inner semiconductive layer, insulating layer and outer semiconductive layer after being heated, so it is easy to peel off. The silicone rubber dust cover can effectively isolate water vapor and impurities, so that the wrapped strip can maintain the cleanliness required by the national standard and fix the strip by applying a certain pressure. On the dust jacket, it can play the role of uniform heat conduction.

In the above heating process, the heating cylinder adopts a staged heating method to transfer heat from the outside to the inside to the three kinds of strip cores, which can take into account the fusion of the three kinds of strips and form a dense outer semi-conductive repair layer and insulation under the action of external pressure. repair layer and inner semiconductive repair layer. The high-frequency induction heating device directly acts on the wire core, and the heat is transferred from the wire core to the original inner semiconducting layer, the original insulating layer and the original outer semiconducting layer from the inside to the outside, so that the outer semiconducting repair layer and the original outer semiconducting layer 1. The junction between the insulation repair layer and the original insulation layer, the inner semi-conductive repair layer and the original inner semi-conductive layer can reach the required temperature and be fully welded and combined, thereby completing the three-layer repair of the core cable at one time.

Since the material used for the outer semiconductive repair layer, insulating repair layer and inner semiconductive repair layer of the fusion-bonded straight-through joint in the above process is completely consistent with the original cable and fully welded, there is no aging of the stress cone in the conventional joint. Discharge breakdown problem caused by water. The whole set of production method is followed by steps such as wire core welding, three-layer fusion of inner semiconductive layer, insulating layer and outer semiconductive layer at the joint, winding copper mesh, wrapping waterproof tape, restoring steel tape armor and outer sheath, etc. The obtained equipment is less, easier to operate, and the obtained straight-through joint can be better connected with the original two cables, and has better insulation strength and waterproof performance. In addition, since the outer semiconductive layer, insulating layer and inner semiconductive layer of the cable core cable are repaired at the same time during the production process, the production efficiency of the joint can be greatly improved.

The manufacturing method of the 10kV to 35kV electric cable process welding type straight-through joint of the present invention is relatively easy to operate and has high production efficiency, and the obtained straight-through joint has better insulation strength and waterproofness.

Description of drawings

Figure 1: Schematic diagram of the structure of a 10kV to 35kV cable;

Figure 2: Schematic diagram of the straight-through joint structure before heating and welding the inner semiconducting layer, insulating layer and outer semiconducting layer;

Figure 3: Schematic diagram of the enlarged structure at A in Figure 2;

Figure 4: Schematic diagram of the straight-through joint structure after the repair of the inner sheath is completed;

Figure 5: Schematic diagram of the straight-through joint structure after connecting the steel armor layer;

Figure 6: Schematic diagram of the through-joint structure after the repair of the outer sheath is completed;

Figure 7: Schematic diagram of the enlarged structure at B in Figure 6.

Among them: 1-outer sheath, 2-steel armor, 3-inner sheath, 4-filling layer, 5-copper shielding layer, 6-outer semiconducting layer, 7-insulating layer, 8-inner semiconducting layer, 9-wire core, 10-heat shrink tube, 11-silicone rubber dust cover, 12-inner semi-conductive repair layer, 13-insulation repair layer, 14-outer semi-conductive repair layer, 15-aluminum foil, 16-imide Adhesive tape, 17-shaping mold, 18-copper mesh, 19-constant force spring, 20-PVC insulating tape, 21-waterproof tape, 22-epoxy resin waterproof glue, 23-copper braided tape, 24-filling tape, 25 - Armored tape.

Detailed ways

The manufacturing method of the 10kV to 35kV cable process fusion type straight-through joint of the present invention will be further described below in conjunction with the accompanying drawings and specific examples. Figure 1 is a schematic structural diagram of a 10kV to 35kV cable. In some places below, the word "original" is added before the name of the structure that originally existed in the cable to distinguish it from the repair material, for example, "original outer semiconductive layer 6" and "outer semiconductive layer 6" refer to is the same structure.

The high-frequency induction heating device used in the embodiment is the DD-25I high-frequency induction heater produced by Shanghai Jubao Electromechanical Technology Co., Ltd.; the heating cylinder used is customized by the relevant manufacturer according to the required size, and is equipped with an intelligent temperature control box and pressure sensor; the waterproof tape used is Scotch 2228 type all-weather professional grade waterproof insulating tape of 3M Company; the filling tape 24 used is the cable accessory filling tape produced by Shenzhen Priman Material Technology Co., Ltd.

Example 1

A method for manufacturing a 10kV to 35kV cable process fusion type straight-through joint, comprising the following steps:

1) Cutting and stripping of the outer layer of the cable: saw two fractures in the radial direction at the butt ends of the two cables, and peel off the outer sheath 1 of 1000mm and 800mm inwards from the cable fractures of the two cables respectively. Measure 50mm outward from the fracture of the outer sheath 1 to keep the steel armor 2, and strip off the rest. Finally, measure 100mm of the inner sheath 3 outward from the fracture of the outer sheath 1 and keep it, and peel off the rest. Cut off the exposed filling layer 4 and wrap the end of the steel armor layer 2 with PVC tape to prevent oxidation.

2) Cutting, stripping and finishing of the core cable: Strip 300mm of copper shielding layer 5, 200mm of outer semiconducting layer 6, 75mm of insulating layer 7 and 60mm of inner semiconducting layer 8 from the cable fracture inward to make the wire core 9 is exposed, and the end of the copper shielding layer 5 is wrapped with PVC tape to prevent loosening. Shave the ends of the outer semiconductive layer 6 and the inner semiconductive layer 8 into a smooth transitional slope and smooth them with a 600-mesh abrasive belt, and cut the ends of the insulating layer 7 into pencil heads, and then smooth them with 800# sandpaper And rinse and blow dry. Use a 600-mesh abrasive belt to remove the insulation residue on the surface of the exposed inner semiconductive layer 8 and polish the surface, then wrap the exposed outer semiconductive layer 6, insulating layer 7 and inner semiconductive layer 8 with polytetrafluoroethylene tape in the opposite direction Two layers for thermal protection. Use a 240-mesh abrasive belt to remove the exposed oxide layer on the surface of the core 9 and the fracture, and wrap and seal it with PVC tape.

3) Presetting of pipe materials: Put two heat-shrinkable tubes 10 on the cable, and put a silicon rubber dustproof cover 11 on each of the three core cables inside the cable.

4) Welding of the wire core: remove the PVC tape outside the wire core 9, straighten the wire core 9, heat and dehumidify it, insert it into a welding mold to fix it, and fill the metal powder of the same material as the wire core 9 in the box welding mold to release heat Welding, and then the welding place is ground to the same diameter as the original cable core 9.

5) Wrapping of strips: Remove the polytetrafluoroethylene high-temperature-resistant tape wrapped around the outer semiconductive layer 6, the insulating layer 7 and the inner semiconductive layer 8, and use the same strip material as the inner semiconductive layer 8 to tightly Wrap the wire core 9 and the original inner semiconductive layer 8 to form an inner semiconductive repair layer 12 whose surface is no more than 1 mm higher than the original inner semiconductive layer 8 and whose two ends cover the slope-shaped end of the original inner semiconductive layer 8; The same tape as the insulating layer 7 (specifically cross-linked polyethylene material) tightly wraps the inner semiconducting repair layer 12, the original inner semiconducting layer 8 and the original insulating layer 7 to form a surface that is 5mm higher than the surface of the original insulating layer 7 and two The insulating repair layer 13 with a smooth transition between the end and the original insulating layer 7, the two ends of the insulating repairing layer 13 cover the pencil-shaped end of the original insulating layer 7; use the same material as the outer semiconducting layer 6 to tightly wrap the insulation The repair layer 13, the original insulating layer 7 and the original outer semiconductive layer 6 surface form the outer semiconductive repair layer 14 with the same thickness as the original outer semiconductive layer 6, and the two ends of the outer semiconductive repair layer 14 cover the original outer semiconductive layer 6 sloped ends.

6) Fusion recovery of the inner semiconductive layer, insulating layer and outer semiconductive layer: move the silicone rubber dust cover 11 to the outer semiconductive repair layer 14, completely cover and tightly wrap the outer semiconductive repair layer 14, The rubber dust jacket 11 is wrapped with a layer of aluminum foil 15 and wrapped and fixed with imide tape 16, and then locked and fixed with a molding mold 17 (as shown in Figures 2 and 3), and then placed in a heating cylinder to heat to form a fusion The outer semiconductive repair layer 14, the insulation repair layer 13 and the strip of the inner semiconductive layer 8 adopt a high-frequency induction heating device to heat the core cable sections near the two ends of the heating cylinder to make the outer semiconductive repair layer 14 and the original outer semiconductive layer 6 1. The insulating repair layer 13 is integrated with the original repair layer 7, the inner semiconductive repair layer 12 is integrated with the original inner semiconductive layer 8, and the pressure in the shaping mold is not lower than 1.8MPa when the heating is finished.

The heating process of the heating cylinder is as follows: evenly increase the temperature for 20 minutes to 100°C and keep the temperature for 8 minutes, then slowly increase the temperature for 20 minutes to 185°C and keep the temperature for 40 minutes; after the heating cylinder is heated to above 100°C, turn on the high-frequency induction heating device and output 350A induction heating at 380V voltage The current inductively heats the core cable sections near both ends of the heating cylinder for 60 minutes (that is, the heating cylinder is heated slowly from 100°C to 185°C for 20 minutes and the heating cylinder is kept at 185°C for 40 minutes at the same time. Cable sections are heated).

7) Restoration of the copper shielding layer: remove the heating cylinder, plastic mold 17, imide tape 16, aluminum foil 15 and silicone rubber dust cover 11, check whether the surface of the outer semi-conductive repair layer 14 is smooth, and then use copper mesh 18 to separate The original copper shielding layer 5 on each core cable is wrapped and connected, and the two ends of the copper net are fixed with a constant force spring 19, and then the three core cables are wrapped and bound together with a PVC insulating tape 20.

8) Restoration of the inner sheath: As shown in Figure 4, wrap the original inner sheath 3 on the outside of the PVC insulating tape 20 with waterproof tape 21 and connect the two cables. Stretch and half-lap wound three layers, then apply epoxy resin waterproof glue 22 evenly on the surface of waterproof tape 21 and cover with a heat shrinkable tube 10, evenly heat the heat shrinkable tube 10 to make it fully shrink and wrap it with waterproof tape 21 Seal both ends of the heat shrink tube 10.

9) Connection of the steel armor layer: as shown in Figure 5, remove the PVC tape wrapped in the original steel armor layer 2 ends and grind off the antirust paint on the surface with a 240-mesh abrasive belt, and connect the two ends with the original steel armor layer Layer 2 overlapped copper braid 23 wraps the heat-shrinkable tube 10 and fixes both ends of the copper braid 23 with a constant force spring 19, then wraps and fixes the two constant force springs 19 with PVC insulating tape 20 to prevent loosening.

10) Restoration of the outer sheath: As shown in Figures 6 and 7, use a 600-mesh abrasive belt to polish the surface of the original outer sheath 1 with a length of 150 mm at the connection ends of the two cables and wrap it with a filling tape 24, and then wrap it with a waterproof tape 21 After connecting the steel armor layer and the outer sheath 1 wrapped with filling tape 24 on the two cables, the waterproof tape 21 needs to be 100% stretched and half-lapped and wound three layers when wrapping, and then waterproofed with epoxy resin Glue 22 is evenly spread on the surface of waterproof tape 21 and covered with another heat-shrinkable tube 10, heat the heat-shrinkable tube 10 evenly to make it fully shrink and wrap both ends of the heat-shrinkable tube 10 with waterproof tape 21, and finally wrap the heat-shrinkable tube 10 with armor tape 25. Wrap 4 layers on the surface of the heat-shrinkable tubing 10 by half-lapping.

Example 2

A method for manufacturing a 10kV to 35kV electric cable process fusion splicing type straight-through joint, this embodiment is completely consistent with the method described in Embodiment 1 except for steps 5) and 6), and the other steps are exactly the same, specifically as follows:

The surface of the insulating repair layer 13 in step 5) is 6 mm higher than the surface of the original insulating layer 7. The heating process of the heating cylinder in step 6) is: uniformly increase the temperature for 24 minutes to 100°C and keep the temperature for 5 minutes, then slowly increase the temperature for 25 minutes to 185°C and keep the temperature for 46 minutes; After the heating cylinder is heated to above 100°C, the high-frequency induction heating device is turned on, and an induction heating current of 350A is output at a voltage of 380V to inductively heat the core cable section near both ends of the heating cylinder for 71 minutes.

Example 3

A method for manufacturing a 10kV to 35kV electric cable process fusion splicing type straight-through joint, this embodiment is completely consistent with the method described in Embodiment 1 except for steps 5) and 6), and the other steps are exactly the same, specifically as follows:

The surface of the insulating repair layer 13 in step 5) is 8 mm higher than the surface of the original insulating layer 7. The heating process of the heating cylinder in step 6) is: uniformly increase the temperature for 30 minutes to 100°C and keep the temperature for 10 minutes, then slowly increase the temperature for 15 minutes to 185°C and keep the temperature for 50 minutes; After the heating cylinder is heated to above 100°C, the high-frequency induction heating device is turned on, and an induction heating current of 350A is output at a voltage of 380V to inductively heat the core cable section near both ends of the heating cylinder for 65 minutes.

National Smart Grid Power Transmission and Distribution Equipment Quality Supervision and Inspection Center (Guangdong) is based on GB/T 12706.4-2008 "Rated Voltage 1kV (U _m = 1.2kV) to 35kV (U _m = 40.5kV) extruded insulated power cables and accessories Part 4: Rated voltage 6kV (U _m = 7.2kV) to 35kV (U _m = 40.5kV) power cable accessories test requirements "stipulations Methods for detection, test items and results are shown in Table 1. It can be seen from Table 1 that the tested test items all meet the requirements, indicating that the performances of the 10kV to 35kV cable technology fusion-type straight-through joints prepared by the method of the present invention all reach the national standard.

Table 1: Inspection items and results

Claims (2)

1. A method for making a 10kV to 35kV cable technology fusion type straight-through joint, characterized in that it comprises the following steps: 1) Cutting and stripping of the outer layer of the cable: saw two fractures in the radial direction at the butt ends of the two cables, and peel off the outer sheath, steel armor layer, Inner sheath and cut off the exposed filling layer; 2) Cutting, stripping and finishing of the core cable: peel off the copper shielding layer, outer semi-conductive layer, insulating layer and inner semi-conductive layer layer by layer from the core cable in the cable, and remove the outer semi-conductive layer. The end of the insulating layer and the inner semi-conductive layer is cut into a smooth transitional slope and polished smooth with a 600-mesh abrasive belt. Remove the insulation residue on the surface of the exposed inner semi-conductive layer with a mesh belt and polish the surface, then wrap the exposed outer semi-conductive layer, insulating layer and inner semi-conductive layer with polytetrafluoroethylene tape in the opposite direction for heat insulation protection ; Use a 240-mesh abrasive belt to remove the exposed core surface and the oxide layer at the fracture, and wrap it with tape to seal it; 3) Presetting of pipe materials: put two heat shrinkable tubes on the cable, and put a silicone rubber dustproof cover on each of the three core cables inside the cable; 4) Welding of the wire core: Remove the tape outside the wire core, straighten the wire core and heat and dehumidify it, insert it into the welding mold to fix it, fill the welding mold with metal powder of the same material as the wire core for exothermic welding, and then put The welding place is ground to the same diameter as the original cable core; 5) Tape wrapping: Remove the high-temperature-resistant tape wrapped around the outer semiconductive layer, insulating layer and inner semiconductive layer, and use the same tape as the inner semiconductive layer to tightly wrap the core surface and the original inner The surface of the semi-conductive layer is higher than the inner semi-conductive layer of the original core cable within 1mm, and the two ends cover the slope-shaped end of the original inner semi-conductive layer; the inner semi-conductive repair layer is tightly wrapped with the same tape as the insulating layer. The semi-conductive repair layer, the original inner semi-conductive layer and the original insulating layer form an insulating repair layer whose surface is 5-8mm higher than the original insulating layer and whose two ends transition smoothly with the original insulating layer. The two ends of the insulating repair layer cover the original insulating layer The end of the pencil head of the layer; use the same material as the outer semi-conductive layer to tightly wrap the insulating repair layer, the original insulating layer and the surface of the original outer semi-conductive layer to form an outer semi-conductive repair with the same thickness as the original outer semi-conductive layer layer, the two ends of the outer semiconductive repair layer cover the slope-shaped end of the original outer semiconductive layer; 6) Fusion recovery of the inner semiconductive layer, insulating layer and outer semiconductive layer: move the silicone rubber dust cover to the outer semiconductive repair layer, completely cover and tightly wrap the outer semiconductive repair layer, Wrap a layer of aluminum foil on the outside of the sleeve and wrap it with imide tape to fix it, then lock and fix it with a plastic mold, and then heat it in a heating cylinder to fuse the strips that form the outer semi-conductive repair layer, insulating repair layer and inner semi-conductive layer , using high-frequency induction heating device to heat the core cable section near the two ends of the heating cylinder to make the outer semi-conductive repair layer and the original outer semi-conductive layer, the insulation repair layer and the original repair layer, the inner semi-conductive repair layer and the original inner semi-conductive layer to fuse One piece, the pressure in the shaping mold should not be lower than 1.8Mpa when the heating is finished; 7) Restoration of the copper shielding layer: Remove the heating cylinder, plastic mold, imide tape, aluminum foil and silicone rubber dust cover, wrap and connect the original copper shielding layer on each core cable with copper mesh and apply a constant force The two ends of the copper mesh are fixed by springs, and then the three core cables are wrapped and bundled together with insulating tape; 8) Restoration of the inner sheath: Wrap the outer side of the insulating tape with waterproof tape and connect the original inner sheath of the two cables. When wrapping, the waterproof tape needs to be 100% stretched and half-lapped and wound for multiple layers, and then the Apply waterproof glue evenly on the surface of the waterproof tape and cover it with a heat-shrinkable tube, heat the heat-shrinkable tube evenly to make it fully shrink, and wrap both ends of the heat-shrinkable tube with waterproof tape; 9) Connection of the steel armor layer: Use a 240-mesh abrasive belt to grind off the anti-rust paint on the surface of the original steel armor layer at the connection end of the two cables, and then wrap the heat-shrinkable copper braid with the two ends overlapping the original cable steel armor layer. The two ends of the braided copper braid are fixed with a constant force spring, and finally the two constant force springs are wrapped and fixed with insulating tape; 10) Restoration of the outer sheath: use a 600-mesh abrasive belt to polish the surface of the original outer sheath at the connection end of the two cables and wrap the filling tape, then wrap the connected steel armor layer and the two cables with waterproof tape. Fill the original outer sheath of the tape. When wrapping, the waterproof tape needs to be 100% stretched and half-lapped to wrap multiple layers, and then the waterproof glue is evenly applied to the surface of the waterproof tape, and another heat-shrinkable tube is placed on it evenly. Heat the heat-shrinkable tube to make it fully shrink and wrap the two ends of the heat-shrinkable tube with waterproof tape, and finally wrap multiple layers of armored tape on the surface of the heat-shrinkable tube. 2. The manufacturing method of 10kV to 35kV electric cable technology fusion type straight-through joint as claimed in claim 1, characterized in that, the heating process of the heating cylinder in the step 6) is as follows: uniformly increase the temperature for 20-30min to 100°C and keep the temperature constant for 5 ~10min, then slowly raise the temperature for 15~25min to 185°C and keep the temperature constant for 40~50min. After the heating cylinder is heated to above 100°C, turn on the high frequency induction heating device and output 350A induction heating current at 380V to the core cable section near the two ends of the heating cylinder Simultaneous heating.