1、 The concept of cabling
　
The concept of cable formation: The process of twisting multiple insulated wire cores into cables according to certain rules.
　
2、 The Meaning of Cabling
　
Cabling is one of the important processes in the production of multi-core cables. Power cables are commonly used as three core, four core (one core is the ground wire), and five core (one core is the ground wire, and the other core is the neutral wire) cables for three-phase power supply. The number of cable cores is controlled to be more (2 to 61 cores more). During the cable forming process, several insulated wire cores are twisted together according to certain rules and directions to form a multi-core cable. In addition to stranding, the cable forming process also includes the filling of gaps between insulated wire cores and the process of wrapping and shielding the cable cores after cable formation.
　
When forming a cable, the stranding form of the insulated wire core adopts a concentric regular stranding. If the diameter of the insulated wire core is completely the same, it is called a symmetrical cable. Cables with different diameters of insulated cores are called asymmetric cables. To avoid the influence of torsional stress on the insulated wire core during the cable forming process, circular insulated wire cores are all twisted and twisted using a cable forming machine or bow shaped cable forming machine with a twisting device.
　
3、 Twisting method of cable formation
　
There are two ways to twist twisted wires and cables, one is to unwind twisted wires, and the other is to not unwind twisted wires.
　
Untwisted stranding is the use of a special device (untwisting device) on a wire reel frame equipped with a payout reel to maintain the reel in a horizontal position during machine rotation. During cable formation, the insulated wire core is only subjected to bending without twisting. Untwisting is often used in the cable forming process of circular insulated wire cores. After the cable is formed, there is no rebound stress in the wire core, which can ensure the accuracy of cable roundness and cable diameter.
　
Non retracting twisted strands are mostly used for the formation of fan-shaped cables. After being tightly pressed by the compression mold, they become plastic deformation, thereby eliminating the original torsional stress and ensuring the roundness of the cable after formation.
　
4、 Cable direction and pitch diameter ratio
　
The direction of cable formation is generally right. The confirmation of the direction of cable formation is based on the forward direction of the cable core. If the twisting cage turns left, it is in the right direction, otherwise it is in the opposite direction.
　
The pitch diameter ratio of cables varies according to different types of cables. Circular cores with cross-linked polyethylene insulation have a larger pitch diameter due to their hard insulation, with a coil size of 30-40; The pitch diameter ratio of PVC insulated power cables with circular cores is also 30-40, and the pitch diameter ratio of fan-shaped wires is 40-50; The core diameter ratio of plastic insulated control cables is specified in national standards, generally not exceeding 16-20.
　
5、 Twist in coefficient and twist in rate
　
Within a pitch of the cable, the ratio of the actual length of the insulated wire core to the pitch length of the cable is called the stranding coefficient (K=L/H);
　
The stranding rate is the ratio of the difference between the actual length of the insulated wire core and the length of the cable pitch within a cable pitch to the length of the cable pitch: λ= (L-H)/H × 100%
　
It is more convenient to use the stranding coefficient K, which is always greater than 1. In this way, after the cable is formed, the actual length of a single insulated wire core increases by one K value, and the resistance of the wire core is proportional to the wire core, that is, the resistance of the wire core also increases by one K value. If the insulation resistance is inversely proportional to the length of the insulated wire core, the insulation resistance of each insulated wire core will be reduced by one K value. From the perspective of reducing the wire core resistance value and increasing the insulation resistance value, it is hoped that the smaller the cable stranding coefficient, the better.
　
The stranding coefficient of the cable is inversely proportional to the square of the pitch ratio. Therefore, the smaller the pitch ratio of the cable, the greater the stranding coefficient of the cable, and the greater the amount of insulation core material used. Otherwise, the opposite is true. From the perspective of saving material usage, it is hoped that the smaller the stranding coefficient of the cable, the better.
　
6、 Wrapping process
　
The production process of wrapping various types of metal or non-metallic materials in a ribbon or linear form and spirally wrapping the conductor cable core or cable core at a specified pitch is known as the wrapping process.
　
7、 Non armored cable wrapping tape
　
In order to prevent deformation of the cable core after cable formation and to prevent adhesion with the sheath and provide isolation, the insulated wire core needs to be wrapped with a tape layer while being formed and filled on the cable forming machine. For non armored plastic insulated cables, 1-2 layers of non-woven fabric tape are commonly wrapped with a cover wrapping method (whether one layer or two layers is used, based on the principle of tight wrapping), with a cover size of 10% to 15% of the bandwidth and a wrapping angle within 25 ° to 40 °.
　
8、 Armor of cables
　
Steel strip armored cables are mainly suitable for direct burial underground and can withstand certain mechanical pressure; Steel wire armored cables are mainly suitable for vertical or drop laying and can withstand large mechanical tensile forces. Armored cables are mainly divided into two types: steel tape armor and steel wire armor, as well as their combined armor methods.
　
If there is shielding material (including overall shielding) on the insulated core of steel strip armored cables, the cable core can be replaced with extruded isolation sleeves instead of inner layer. If there is no metal shielding layer on the insulated core, extruded or wrapped inner layer can be used. The inner layer of the wrap is generally made of PVC or PE or similar tapes.
　
Steel wire armored cables generally use extruded inner layer.
　
The model of armored cable, such as YJV22, will have two numbers, and the first number is the armor code: generally, there are three numbers: 2, 3, and 4:
　
2- Refers to double-layer steel strip armor
3- represents thin steel wire armor
4- represents thick steel wire armor
　
The steel strip thickness and copper gap of armored cables, as well as the steel wire diameter and gap of steel wire armored cables, should comply with relevant standards.