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Straight Through Joint in Cable Accessories

2022-02-12
At present, most of the prefabricated cable accessory Straight Through Joint of 110kV and above cross-linked cables are used at home and abroad, because they are all prefabricated structural materials as a whole, and the wrapping type joints and assembled prefabricated joints used in the early days have been rarely used.  

The integral Prefabricated Joint is a prefabricated part of the joint which preforms the semi-conductive inner shield, main insulation, stress cone and semi-conductive outer shield into a whole in the factory.  The installation process is simple and the installation time is short as long as the whole joint is prefabricated and covered on the cable insulation.  At the same time, as the joint insulation is an integral prefabricated part, the joint insulation can be tested for manufacturing quality.  

The whole Prefabricated Joint produced by different manufacturers, although the structure is the same, but the installation process is different, mainly including the following: 

1.Before the conductor is connected, the connector is prefabricated on the outer shielding layer on the side of the connected cable.  After the conductor is connected, drag the prefab to its final position.  One disadvantage of this process is that when the joint preform moves back and forth on the outer semi-conductive layer, it is possible that the particles of semi-conductive material on the cable (left over from the sandpaper polishing of the cable insulation shielding layer during installation) may be brought to the insulation, affecting the insulation level of the interface.  Although silicon grease was coated on the interface between the prefabricated parts and the cable during installation, and the time from the sleeve to the prefabricated parts to the final position should not exceed 2h in the process, this risk still exists, and special attention should be paid to the installation.  

2.Before conductor connection, the liner is mechanically pushed into the prefab to enlarge the inner diameter of the prefab.  Then the expanded prefabricated parts are covered on the outer semi-conductive layer of the cable.  After connecting the conductor, move the prefab to the final position and then pull out the expanding tube.  There is no possibility of bringing semi-conductive material to the insulation.  The other method is to enlarge the inner diameter of the prefabricated parts, and directly set the connector to the outer sheath of the cable. This process not only solves the above problems, but also shortens the stripping size of the outer sheath and shortens the length of the joint.  

3.The joint is expanded with compressed gas (nitrogen), that is, nitrogen is charged between the joint and the cable to form an air film, and the joint is pushed to a predetermined position.  Having a film of gas at the interface reduces friction and does not bring semi-conductive material to the insulating layer.  

dry outdoor termination

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