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Cold shrink cable terminal production process

Time:2019/10/8 posted:

The cold-shrinkable cable terminal is made of an elastomer material (commonly available with silicone rubber and ethylene-propylene rubber) for injection molding in the factory, and then expanded and lined with plastic spiral supports to form various cable accessories. For on-site installation, these pre-expanded parts are placed at the end or joint of the treated cable, and the plastic spiral strips (supports) supported by the inside are taken out and pressed against the cable insulation to form a cable attachment. Because it is elastic retractive force at normal temperature, rather than heat shrinkable cable accessories like heat shrinkage, it is commonly known as cold shrink cable accessories. The early cold-shrink cable terminations were only made of silicone rubber cold-shrinked parts for additional insulation, and the electric field treatment still used stress cone type or stress band wrapping.

Cold shrinkage stress control tubes are now commonly used with voltage ratings from 10kv to 35kv. Cold-shrink cable termination head, 1kv class uses cold shrinkable insulation tube for reinforced insulation, 10kv class uses joint cold shrink insulation with inner and outer semi-conductive shielding layer. The cold-shrink branch sleeve is used for the fork of the three-core cable terminal.

The cold-shrinkable cable terminal has the advantages of small size, convenient operation, rapid operation, no special tools, wide application range and few product specifications. Compared with the heat-shrinkable cable accessory, it does not need to be heated by fire, and the movement or bending after installation does not cause the risk of disengagement between the inner layers of the accessory like the heat-shrinkable cable accessory (because the cold-shrink cable end is elastically biased) Tight). Compared with the prefabricated cable accessories, although the elastic pressing force is used to ensure the internal interface characteristics, it does not correspond to the cable cross section like the prefabricated cable accessories, and has many specifications.

It must be pointed out that the components of the prefabricated cable attachment are tension-free before being installed on the cable, and the cold-shrinkable cable terminations are under high tension, so it must be ensured that during the storage period, the cold-shrinkable parts should not There is obvious long-term deformation or elastic stress relaxation. Otherwise, it will not be able to ensure sufficient elastic pressing force after being installed on the cable, so that good interface characteristics cannot be guaranteed.

The following is a brief introduction to the structure, installation process and precautions of 10 lv and 35 kv cold-shrink cable terminations and 10 kv cold-shrink cable terminations.

1.10kv three-core cable cold shrink cable termination head

 

(1) Strip the outer sheath of the cable, the steel strip (if there is a steel strip), the inner sheath and the core filler according to the size specified in the installation instructions provided by the manufacturer (the stripping length of the strip is mainly determined by the allowable bending radius of the core) Determined by the specified distance between the two, but with the length of the cold-shrinkable sheath tube on the set of cores provided. The inner sheath stays 10mm and the steel strip leaves 25mm. Then wipe the end of the cable about 50mm long and wipe the outer cover.

 

(2) Install the ground wire. A grounding copper ring is respectively mounted on the core copper shield at about 65 mm above the steel strip, and the grounded braided copper wire and the three copper strips are fixed together on the steel strip by a constant force spring. If the steel strip and the core shield are required to be grounded separately, another 10mm2 braided copper wire should be fixed on the steel strip with a constant force spring, then covered with an insulating tape, and then the core shielded the ground braided copper wire and the three cores. The grounding copper strip is connected to the lead.

 

Note: The steel ground wire and the core shield ground wire must not have electrical connection in the terminal. In order to prevent water vapor from entering the cable along the grounding wire, first cover the outer sheath with 2 layers of waterproof tape, sandwich the grounding wire in the middle, and then pack 2 waterproof tapes on the outside.

 

(3) Install the cold shrink branch sleeve. Place the cold shrinking branch sleeve on the core splitting branch, first pull out the inner plastic spiral strip at the lower end, and then pull out the inner plastic spiral strips of the three finger tubes, and shrink and compress the wire core fork.

 

(4) Install a cold shrink jacket tube. The three cold-shrinkable sheath tubes are respectively placed on the three cores, and the lower part covers the branch sleeves 15mm, and the plastic spiral strips in the tubes are taken out, and the inner core copper shield is shrunk and compressed. In the case of an elongated indoor terminal, the second cold-shrinkable sheath tube is contracted in the same manner, and the lower end is overlapped with the ** root by 15 mm. The length from the end of the sheath tube to the end of the core should be equal to the size specified in the installation instructions.

 

(5) Leave a copper shield upward from the sheath pipe mouth (45mm for the outdoor terminal head, 30mm for the indoor terminal), and the rest are stripped.

 

Leave a 10mm semi-conductive layer, peel off the remaining semi-conductive layer, and strip the core end insulation by 1omm deep in the terminal hole.

 

(6) Starting from the end of the steel shielding tape 10 mm from the end of the semi-conductive tape until covering the cable insulation 10 mm, and then returning to the copper shielding tape, a smooth transition (no obvious step) is required at the junction of the semi-conductive tape and the insulation.

 

(7) Crimp terminal block.

 

(8) Install cold shrink insulation. First clean the cable insulation and the terminal at the crimping point with a cleaning agent. Apply a small amount of silicone grease to the surrounding semi-conductive tape and the nearby insulating surface. Insert the cold shrink insulating member to the position specified in the installation manual, pull out the plastic spiral strip, and shrink and compress the cable insulation. (If the width of the terminal flat plate is larger than the inner diameter of the cold shrink insulating member, the cold shrink insulating member should be installed first, then Crimp terminal block).

 

(9) Wrap the gap between the terminal and the core insulation with an insulating rubber tape, and wrap the leak-proof tape on the outside.

 

(10) In the three-phase wire core branching, the finger tube is wrapped around the phase color marking tape.

 

2.35kv single core cable terminal

 

Compared with the 10kv three-core cable terminal, the structure and process are simple. It is not necessary to install the branch sleeve and the sheath tube on the core. The rest and the three-core cable terminal are basically the same.

 

3.10kv three core cable connector

 

The installation process is similar to the prefabricated joints, but the following differences should be noted:

 

(1) When the cold shrink joint main body is placed on the cable core of the end which is peeled off longer, the tap of the plastic spiral strip should face the branch of the end cable core.

 

(2) After all the relevant components are placed on the cable core, the cable conductors and crimping pipes at both ends do not have to be crimped twice like the preform connectors.

 

(3) Before moving the cold shrink joint main body to the middle of the joint, uniformly apply the special mixture provided by the manufacturer at the junction of the semiconductive layer and the insulation and the insulating surface.

 

(4) Install shielded copper mesh bridge wire and steel strip jumper, usually fixed by constant force spring.

 

(5) The cold shrink joint is wrapped with a semi-overlay with a waterproof tape. The two ends cover the outer sheath of the cable for 60mm, and then wrap the entire joint surface with the armor. After curing, it has good mechanical protection. This pin tape is a pre-impregnated curable black polystyrene fiberglass braided tape, vacuum packed. Open the package before use, pour water for 15s, pour out the water, and use. Other suitable protective layers or protective boxes can also be used.

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