Popular Science Lesson: Thermal Shrinkable Cable Joints

Heat-shrinkable cable joints are cable joints manufactured using a complete set of heat-shrinkable cable accessories. These accessories are made from rubber and plastic materials using special processes and include heat-shrinkable insulating tubes, heat-shrinkable semi-conductive tubes, heat-shrinkable oil-resistant tubes, heat-shrinkable sheathing tubes, heat-shrinkable branch tubes, and heat-shrinkable rain skirts. Due to their relatively simple manufacturing process, they are widely used for the termination and intermediate joints of various rubber and plastic cables with different voltage ratings. Their internal structure is similar to that of wrapped cable joints.

Schematic diagram of 10kV XPEL cable heat-shrinkable single-phase intermediate joint and outdoor terminal structure

(a) Single-phase intermediate joint structure diagram; (b) Outdoor terminal structure diagram
1—Conductor; 2—Inner semiconductive layer; 3—XLPE insulation layer; 4—Outer semiconductive layer; 5—Copper shielding tape; 6—Connecting tube; 7—Stress control tube; 8—Inner insulation tube; 9—Outer insulation tube; 10—Shielding tube; 11—Semiconductive tape; 12—Filling adhesive; 13—Stress relief adhesive; 14—Sealant; 15—Copper shielding mesh; 16—Copper braided tape; 17—Binding wire; 18—Terminal; 19—Cable core wire; 20—Sealing tube; 21—Cable insulation layer; 22—Outdoor heat-shrinkable tubing; 23—Single-hole rain skirt; 24—Stress tube; 25—Cable semiconductive layer; 26—Cable copper shielding layer; 27—Three-hole rain skirt; 28—Three-way branch sleeve; 29—Grounding wire; 30—Cable clamp

Schematic diagram of 35kV single-core extruded heat-shrinkable intermediate joint and terminal structure

(a) 35kV single-core extruded heat-shrinkable intermediate joint structure
(b) 35kV single-core extruded heat-shrinkable terminal structure

1, 20—Cable sheath; 2, 19—Copper shield; 3—Stress relief adhesive; 4—Semi-conductive layer; 5—Stress control tube; 6—Core insulation; 7—Semi-conductive tape; 8—Connecting tube; 9—J30 self-adhesive tape; 10—Inner insulation tube; 11—Outer insulation tube; 12—Semi-conductive tube; 13—Copper shielding mesh; 14—Sheath tube; 15—Terminal; 16—Sealant; 17—Sealing tube; 18—Insulation tube; 21—Ground wire

Cold shrink cable joints are cable joints or terminations made with a set of cold shrink cable accessories. They are typically made of silicone rubber or ethylene/propylene rubber, allowing for natural shrinkage. Normally, a spiral plastic support strip is used to maintain the inner diameter and shape of the accessory before use. During field installation, simply slip the accessory onto the cable joint (terminal or intermediate point), pull out the plastic support strip, and the rubber accessory will tightly shrink onto the corresponding part of the cable. The entire process requires no heating, simplifying the installation process. Currently, cold shrink accessories are mainly used on cables with voltage levels of 35kV and below, as shown in the figure.

Schematic diagram of cold-shrink cable joint structure

(a) Material of cold-shrink cable joint; (b) Cross-sectional view of single-core joint; (c) Cross-sectional view of three-core joint;
1—Cable; 2—Cable insulation layer; 3—Stress pile; 4—Shielding tube; 5—Copper connecting tube; 6—Supporting liner; 7—Steel armor; 8—Inner sheath of cable; 9—Constant force spring; 10, 11—Outer semiconductive layer; 12—Core insulation layer; 13—Inner semiconductive layer; 14—Conductor connecting hardware; 15—Copper shielding mesh; 16—Grounding wire; 17, 18—Special armored waterproof tape; 19—Armor tape

Schematic diagram of cold shrink cable termination structure

(a) Cold shrink termination material
(b) Cross-sectional view of three-core termination

1—Cold shrink cable termination; 2—Cold shrink three-finger sleeve; 3—Cold shrink sheath; 4—Cold shrink sealing tube; 5—Conductor connection hardware; 6—Elastic sealing tape; 7—Insulation layer; 8—High dielectric constant electrical stress control stack; 9—Semiconductive layer; 10—Phase color band; 11, 12—Copper shielding layer; 13—Filling adhesive; 14, 15—Constant force spring; 16—Grounding wire