2025-11-24
In power transmission and distribution lines, a complete power cable line consists of two main parts: the cable body and the cable joints. Cable joints are a crucial component of power cable lines. During cable installation, laying, and operation, the failure rate of cable joints is often much higher than that of the cable body. Therefore, analyzing and understanding the condition of cable joints is essential.
According to their purpose, cable joints are generally classified into two types: terminal joints and intermediate joints.
Terminal joints can be further divided into the following three types:
(1) Indoor terminal joints. Used indoors to connect the cable to the power supply equipment. Their appearance is shown in Figure (a).
(2) Outdoor terminal joints. Used outdoors to connect the cable to the power supply equipment. Their appearance is shown in Figure (b).
(3) Equipment terminal joints. Used when connecting the cable to electrical equipment, with the high-voltage conductive metal in a fully insulated and enclosed state.
There are three main types of intermediate joints:
(1) Butt Joint: Two identical or different cables are directly butted together, as shown in Figure (a).
Schematic diagram of cable intermediate joints: (a) Butt Joint; (b) T-Joint; (c) X-Joint
(2) Branch Joint: Connecting a branch cable at a point on the main cable is called a T-Joint. When two branch cables simultaneously branch off at a point on the main cable, it is called an X-Joint. T-Joints and X-Joints are shown in Figures (b) and (c).
(3) Transition Joint: The connection between two cables with different insulation types (such as cross-linked polyethylene cable and oil-impregnated paper-insulated cable).
