What is the function of each step of the cold shrink cable head

A 10kV three-core high-voltage cable as an example to talk about the cable structure" has the order from inside to outside: copper core wire, semiconductor layer, insulation layer, semiconductor layer, copper strip shielding layer, filling layer, sheath layer. Focus on the semiconductor layer, which is the key to the production process of the cable head, a little attention can be seen that the semiconductor layer is set between the metal and the insulation, which involves the factors of electric field stress, the space is limited, without explanation, and non-professionals can not understand, directly speaking, it is a transitional role.

Now when it comes to the production steps, there is nothing special, each manufacturer of cold shrinkable cable head has installation steps and cutting and stripping size when leaving the factory, especially the size, each manufacturer is formulated according to its own cold shrink head size, and each manufacturer is different. The installation process is actually a process of gradually recovering the structure of each layer of the cable from the inside out, in addition to paying a little attention to the lap position of the semiconductor layer, many cable head insulation can not be shaken up, most of them are not done well in this regard, in the production process, strictly according to the instructions and size of the installation, pay attention to moisture, and cleaning. It's tiring to answer so much, but this should be the most popular and practical answer that you can give in it.

1. Peel off the outer sheath to straighten and wipe the cable. Strip the outer sheath from the mounting position to the terminal block (the constant force spring can be temporarily wound around the cut-off of the outer sheath to facilitate the removal of the outer sheath). 2. Saw the steel armor temporarily tie the steel armor with a constant force spring along the steel armor, and then saw an annular deep mark along the direction of the steel armor, do not cut the second layer of steel armor to prevent injury to the cable, pry it up with a flathead screwdriver (the steel armor edge is disconnected), and then use pliers to pull down and loosen the steel armor, take out the steel armor belt, and deal with the burr at the sawing place.

The whole process must follow the direction of the steel armor wrapping, and the steel armor on the cable cannot be loosened. 3. Peel off the inner sheath: key points:

Prevent scratching the copper screen to retain 30mm of steel armor, 10mm of inner sheath, and wrap the steel armor with wire tie or PVC tape to prevent loosening. The copper shield ends are tightened with PVC tape to prevent loosening and scratching the cold shrink tubing. 4. Install the steel armor grounding wire, stuff the triangle gasket cone into the cable bifurcation, remove the paint and rust on the steel armor, and fix the steel armor ground wire on the steel armor with a large constant force spring.

In order to fix firmly, the ground wire should be reserved for 10 20mm, and after the constant force spring is wound once, the reserved part is folded backwards, and then wound with the constant force spring. 5. Wrap the filler from 50mm below the fracture to the entire constant force spring, steel armor and inner sheath, wrap two layers with filler, and wrap one more layer at the three-way mouth, so that the cold shrinkage finger sleeve is full and full. 6. Fix the copper shield grounding wire, divide one end into three strands of ground wire, and fix it on the three-phase copper shield with three small constant force springs.

Separate the steel armor ground wire from the copper shield ground wire and do not short it. 7. Install the cold shrinkable 3-core branch. 8. The set of cold shrink sheath tube can be wrapped with a layer of black self-adhesive tape outside the filler and small constant force spring, so that the plastic strip in the cold shrinkable finger sleeve is easy to be withdrawn.

Pull out the three small support tubes at the end of the finger slightly (aligned with the root of the finger from the inside), then put the finger sleeve in and press down as much as possible, and pull out the plastic strip at the end counterclockwise. After cleaning the shielding layer, wrap the PVC tape within 100mm of the end of the finger sleeve, put the cold shrinkable tube to the root of the finger sleeve, pull out the plastic strip counterclockwise, hold the end of the cold shrinkable tube with your hand when pumping, loosen it after positioning, do not hold the unshrunken cold shrink tube all the time, cut or lengthen the cold shrink tube or cut off the excess core according to the distance from the end of the cold shrink tube to the terminal. 9. Strip the copper shield layer at the bifurcation of the cable core and mark the hue, according to the cable accessories manual, correctly measure the position of the copper shield cut-off, (wrap it with PVC tape to prevent the copper shield from loosening), or tie it tightly with copper wire on the inside of the cut-off place, and make a shallow mark along the copper wire with a knife along the direction of the copper belt tightening (note that the semiconductor layer cannot be cut), slowly tear off the copper shielding tape, and finally untie the copper wire along the direction of the copper belt.

10. Peel off the outer semi-conductive layer at a distance of 10-20mm from the fracture of the copper strip (subject to the size specified in the manual) for the fracture of the outer semi-conductive layer, and wrap a circle of tape on the inside of the fracture for marking. Peelable outer semi-conductive layer treatment method: At the predetermined stripping of the semi-conductive layer (outside of the tape), a ring mark is made with a knife skin, and the ring is removed.

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1. The design principle of the cross-linked cable head.

First of all, the design principle of all cross-linked cable heads should follow the principle of restoring the cable body structure. Therefore, the design idea of the joint should comply with the electrical standards of GB12706-4 and IEC60502-4:1997 in China, and must meet its electrical, physical and chemical properties to ensure the normal operation of the cable head for a long time and the safe operation of electrical equipment.

Second, the difference between cold shrinkable cable head and heat shrinkable cable head.

The structural cross-linked cable is composed of the outer sheath, metal armor, inner sheath, filler, copper shielding layer, outer semi-conductive layer, insulation layer, inner semi-conductive layer, conductor, money core, etc. Therefore, what kind of cable structure needs to have what kind of material and its process of cable accessories and it correspond and match.

PrincipleThe design principle of the cable head should meet the requirements that can be met and met: so that the cable can operate safely in any natural environment. In order to achieve this, four key factors need to be taken into account, namely:

1) sealing, (2) insulation, (3) electric field, (4) process and other elements, which are also the four important problems to solve the cable head.

1) Since most of the cable heads are installed in outdoor overhead, direct burial and other environments, waterproof and moisture-proof have become one of the keys to ensure the safe operation of the cable head, and its sealing performance and method should be considered. At present, there are usually two sealing methods: one is the method of potting with asphalt or epoxy resin, which is complex, difficult to control, and not conducive to maintenance; Another new method is also the preferred method for domestic and foreign professional manufacturers.

Heat Shrink Cable Termination Features:

Heating and shrinking of parts is a key part of the quality of heat shrink head manufacturing. Heating tools can be high-power electric hair dryers or blowtorches. Placing the cable vertically before heating is conducive to heating operation and uniform shrinkage of components.

When heating, it should be noted that the heating shrinkage temperature is ll0 to 120. Adjust the blowtorch flame to a soft yellow flame, beware of the high temperature blue flame.

Cold Shrink Cable Terminations:

The cold shrink method eliminates the hassle and insecurity of flame heating used in heat shrink products. For heat shrinkable products, the cold shrinkable cable accessories use the principle of expansion support, and the support can be automatically shrunk and reset when the support is removed, and it is called cold shrinkage without heating, which is very convenient to use.

Cold shrinkable cable accessories are made of elastomer materials (commonly used silicone rubber and ethylene propylene rubber), injected vulcanized in the factory, and then expanded and lined with plastic spiral supports to form various cable accessories. For on-site installation, these pre-expanders are placed at the end of the treated cable or joint, and the plastic spiral strips (supports) with internal support are extracted and pressed against the cable insulation. Because it relies on elastic retraction force at room temperature, rather than heating and shrinking like heat shrinkable cable accessories, it is commonly known as cold shrinkable cable accessories.

It must be pointed out that before being installed on the cable, the parts of the prefabricated cable accessories are not tensile, while the cold-shrinkable cable accessories are in a high-tension state, so it must be ensured that during the storage period, the cold-shrinkable parts should not have obvious permanent deformation or elastic stress relaxation, otherwise it cannot be guaranteed that there is enough elastic compression force after being installed on the cable, so that good interface characteristics cannot be guaranteed.