In power systems, it is usually necessary to lay a cable for the transmission of electricity or to realize the power supply to the user. After the cable is laid, the cables must be connected as a whole to make it a continuous line, which is called a cable connector. The cable connector in the middle of the cable line is called the cable middle connector.
Cable intermediate connectors are cable accessories for intermediate connections of XLPE cables or oil-immersed cables for various voltage levels, the main role is to make the power supply lines unobstructed, so that the cable to keep the seal, and to ensure that the cable joints at the insulation level, so that its safe and reliable operation, played a waterproof, dustproof and shockproof action. In order to ensure the reliability of power supply, it is required that the rubber stress cone and the preformed rubber insulating parts in the cable middle joint should be free of bubbles, burnt and other harmful impurities, smooth internal and external surfaces, good combination of insulation and semi conductive interface, and no harmful impurities in the semi conductive shielding. According to the microscopic observation results of the existing cable intermediate joint samples and the investigation of cable accessory manufacturers, the small bubbles and interfacial bulge on the indirect head of the cable are unavoidable, so to ensure the reliability of the power supply and ensure the quality of the cable's middle joint, we need to have a corresponding method to detect the internal defect of the cable's middle joint.