In the installation of power engineering, cable terminals and intermediate joints are important parts of power equipment in power transmission and transformation cable lines. They are used to disperse the electric field at the cut off point of the external shield of cable terminals, protect the cable from breakdown, and also serve as internal and external insulation and waterproof. In cable lines, more than 60% of accidents are caused by accessories, so the quality of connector accessories plays a very important role in the safety and reliability of the entire power transmission and transformation.
1. The connection of conductors The connection of conductors requires low resistance and sufficient mechanical strength, and there shall be no sharp corners at the joints. Crimping is commonly used for conductor connection of medium and low voltage cables. Attention shall be paid to crimping:
(1) Select conductor connecting pipe with proper conductivity and mechanical strength;
(2) The fit clearance between the inner diameter of the crimping tube and the outer diameter of the connected wire core is 0.8-1.4mm;
(3) The joint resistance after crimping shall not be more than 1.2 times of the conductor with equal section, and the tensile strength of copper conductor joint shall not be less than 60N/mm2;
(4) Before crimping, the outer surface of the conductor and the inner surface of the connecting pipe shall be coated with conductive adhesive, and the oxide film shall be damaged with a wire brush;
(5) Sharp corners and burrs on connecting pipes and core conductors shall be polished with a file or sandpaper.
2. Internal semiconductor shielding treatment Where the cable body has an internal shielding layer, the internal shielding layer of the connector of the crimping tube conductor must be restored when making the connector. A part of the internal semiconductor shielding of the cable must be reserved so that the shielding in the connector on the connecting tube can be connected with each other, ensuring the continuity of the internal semiconductor, so that the field strength at the connector can be evenly distributed.
3. Treatment of external semiconductor shielding The external semiconductor shielding is a semi conductive material that plays the role of uniform electric field outside the cable and connector insulation. Like the internal semiconductor shielding, it plays a very important role in the cable and connector. The external semiconductor port must be neat and uniform, and it is also required to have a smooth transition with the insulation, and add semiconductor tape around the connector to connect with the external semiconductor shield of the cable.
4. Treatment of cable reaction force cone During construction, the shape of the reaction force cone is as accurate as possible. The potential distribution on the entire cone surface is equal. When making the cross-linked cable reaction cone, special cutting tools are generally used, or you can heat it slightly with a light fire, and use a sharp knife to cut. After the base is formed, it is scraped with 2mm thick glass, and finally polished with sandpaper from coarse to fine until it is smooth.
5. Metal shielding and grounding treatment The role of metal shielding in cables and connectors is mainly used to conduct cable fault short circuit current, as well as electromagnetic interference of shielding electromagnetic field on adjacent communication equipment. The metal shielding is at zero potential in a good grounding state under operation. When the cable fails, it has the ability to conduct short circuit current in a very short time. The grounding wire shall be reliably welded, the metal shield and armor tape on the cable body at both ends of the box shall be firmly welded, and the grounding of the terminal shall be reliable.
6. Sealing of joints and mechanical protection Sealing and mechanical protection of joints are the guarantee to ensure safe and reliable operation of joints. Water and moisture shall be prevented from seeping into the joints. In addition, joint protection grooves or cement protection boxes shall be erected at the joints.
