In the power engineering installation, the cable terminal and the intermediate cable connector are important electrical equipment components in the power transmission and distribution. Its role is to disperse the electric field at the shielding cut off of the cable terminal and protect the cable from breakdown. It has internal and external insulation and waterproof functions.
In cable lines, more than 60% of accidents are caused by accessories, so the quality of joint accessories plays a very important role in the safety and reliability of the entire transmission and transformation. The following is the analysis of the main points of installing cable joints in electric power construction.
The conductor connection requires low resistance and sufficient mechanical strengths. The connection of medium and low voltage cable conductors is usually crimping. When crimping, pay attention to choose a suitable connecting tube with conductive and mechanical strength; Before crimping, the outer surface of the conductor and the inner surface of the connecting pipe are coated with conductive glue; The sharp corners, burrs, etc. on the connecting pipe and core conductor should be smoothed with a file or sandpaper.
The function of metal shielding in cables and connectors is mainly used to conduct cable fault short-circuit current,and shield the electromagnetic interference of electromagnetic fields on nearby communication equipment.
In the running state, the metal shield is at zero potential in a good grounding state. When the cable fails, it has the ability to conduct short-circuit current in a very short time. The ground wire should be reliably welded, the metal shield on the cable body at both ends of the box and the armor tape should be firmly welded, and the terminal head should be firmly grounded.
The sealing and mechanical protection of the joint are the guarantee to ensure the safe and reliable operation of the joint. Moisture should be prevented from entering into the cable joints. In addition, joint protection grooves or cement protection boxes should be built at the joints.
Where the cable body has an inner shield layer, a part of the inner semiconductor shield of the cable must be left in order to allow the inner shield of the connector on the connection pipe to communicate with each other, ensure the continuity of the inner semiconductor, and thereby make the field strength at the joint uniform distributed.
The outer semiconductor shield is a semi-conductive material that acts as a uniform electric field on the outside of the insulation of cables and cable joints. Like the inner semiconductor shield, it plays a very important role in cables and joints.
The outer semiconductor port must be neat and uniform, and smooth transition with insulation is required, and the semiconductor tape at the cable connector is overlapped with the semiconductor shield of the cable body.
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