Integral prefabricated joints are by far the most common type of cross-linked cable joints. The factor that has the greatest impact on the quality of the joint during field installation is the site-specific installation tools. The quality of prefabricated parts should be completed in the factory with electrical tests and reliable quality. According to the characteristics of different prefabricated parts, special field installation tools are used, including field reaming and traction. Figure 6-22 shows a schematic diagram of a typical monolithic prefabricated part. The following focuses on the construction points of such cable joints.
1. General Requirements
(1) Before the joint, the quality, quantity, and specifications of the installation materials should be checked.
(2) Cable insulation and preforms should be cleaned and completely dry before the final positioning of the insulated preforms.
(3) After the cable insulation is polished, it should be carefully inspected to ensure that the surface of the insulation is free of damage.
(4) Cable joint materials shall be stored in a dust-free, low humidity (%) indoor environment with a temperature not exceeding 40 °C. Long-term exposure to sunlight is strictly prohibited.
(5) All joint materials should be used within their expiration date.
2. Grinding Treatment of Insulation and Insulation Shield
(1) Wrap two layers of PVC tape around the insulation layer at the junction of cable insulation and insulation shield as protection to prevent grinding of the insulation layer.
(2) Sand the insulation surface at the boundary of the cable insulation and insulation shield with 120 meshes, 240 meshes, and 320 mesh sandpaper (applicable to 110kV voltage level).
(3) Check the diameter of the cable insulation at 6 places with vernier calipers.
(4) Caution. Each place should be measured twice in horizontal and vertical directions to ensure that the actual size of the cable insulation layer meets the process requirements. ② To ensure that the cable insulation layer is round, the difference between the measurement results in two directions should be less than 0.5 mm. ③ The outer diameter of the polished insulation layer should be controlled within the allowed value.
(5) When the inspection results meet the requirements, polish the cable insulation layer with 400 mesh sandpaper. Finally, tear off the PVC tape on the insulation shield layer and continue polishing from the insulation layer to the insulation shield layer.