In power systems, cables are usually required to transmit electricity or to supply power to users. After the cable is laid, in order to make it into a continuous line, each section of the cable must be connected as a whole, these connection points are called cable connectors. The PG Cable Gland in the middle part of the cable line is called the cable intermediate joint. Cable intermediate connector is used for all kinds of voltage level of cross-linked cable or oil-immersed cable intermediate connection cable accessories, the main role is to make the power supply line unobstructed, to keep the cable sealed, and to ensure the insulation level at the cable junction, so that it can operate safely and reliably, play a waterproof, dust-proof and vibration-proof role.

In order to ensure the reliability of power supply, it is required that the rubber stress cone and prefabricated rubber insulators in the Copper Cable Gland should be free of bubbles, scorch and other harmful impurities, the inner and outer surfaces should be smooth, the insulation and semi-conductive interface should be well combined, and the semi-conductive shielding should be free of harmful impurities. According to the microscopic observation results of the existingPG Cable Gland samples and the investigation of the cable accessories manufacturer, it is found that the tiny bubbles and the interface bulge on the PG Cable Gland are unavoidable. Therefore, in order to ensure the reliability of power supply and the quality of the cable intermediate joint used, it is necessary to detect the PG Cable Gland correspondingly. Methods of internal defects.

At present, the method of detecting the internal defects of the PG Cable Gland is mainly the electrified partial discharge test. When partial discharge occurs in insulating structure, electrical pulse and electromagnetic radiation will be generated, so the abnormal signals generated by partial discharge can be directly received by the signal receiving probe and the abnormal signals can be analyzed to determine the location of internal defects. The principle of judging the position of internal defect by the method of live partial discharge test is that the position of internal defect of the Copper Cable Gland is determined by the strength of the abnormal signal generated by the received signal receiving probe according to the partial discharge of the cable intermediate joint, but the abnormal signal is usually strong. Attenuation characteristics. Therefore, judging the location of internal defects according to the strength of abnormal signals requires that the installation position of the signal receiving probe should be close to the location of internal defects, and the accuracy of the signal receiving probe should be high. However, it is difficult to predict the location of internal defects and the accuracy of the existing signal receiving probe. Limited, it is difficult to detect some small defects inside the cable intermediate gland, which leads to the low accuracy of live partial discharge testing method to detect the internal defects of cable intermediate gland.

This new method solves the technical problems of low precision and difficult to detect some small defects inside the Copper Cable Gland.

Based on the transmission and reflection characteristics of ultrasonic wave, the ultrasonic probe is attached to the outside surface of cable gland, and the ultrasonic signal is transmitted to the inside of cable gland and the ultrasonic reflection signal is received. The time difference between two cables can determine whether there is internal defect detection in cable glands.