Advantages of cable for AC withstand voltage test

       With the development of the national economy and the increase of the power supply voltage level of the city network, the XLPE insulated power cable (XLPE) has been acquired at home and abroad for its reasonable process and structure, excellent electrical performance and safe and reliable operation characteristics. The more widely used. Especially in the field of high voltage transmission, great progress has been made. Compared with oil-filled cables, cross-linked cables are easy to lay and install, easy to operate and maintain, and there is no turbulence of oil. However, recent years of operation and research have shown that the insulation of XLPE cables is prone to dendrite discharge during operation, causing insulation aging damage, which seriously affects the service life of XLPE insulated power cables. Therefore, fully understanding the insulation characteristics of cross-linked cables, and timely and effectively discovering and preventing certain defects in insulation are of great significance for ensuring the safe operation of equipment and even systems. The main factors affecting the insulation of the cross-linked cable and the principle of the handover test of the cable are expounded. It is considered that it is necessary and feasible to carry out the AC withstand voltage test on the cross-linked cable in the field.

        In order to ensure the safe and reliable operation of the cable, the relevant international standards have clearly defined the various tests of the cable. The main test items include: measuring insulation resistance, DC withstand voltage and leakage current. Among them, the measurement of the insulation resistance is mainly to check whether the insulation of the cable is aging, damp, and insulation defects exposed in the withstand voltage test. The DC withstand voltage and leakage current tests were performed simultaneously, and the purpose was to find defects in the insulation.

        However, in recent years, domestic and foreign experiments and operational experience have proved that the DC withstand voltage test can not effectively find the insulation defects in the cross-linked cable, and even cause the cable insulation hazard. Germany Sechiswag company experienced 87 faults in the 10 kV voltage class XLPE cable of 41 circuits from 1978 to 1980; Sweden’s 3 kV to 24.5 kV voltage class XLPE cable was put into operation more than 9 000 km, and 107 faults occurred. There have been many cable accidents in China, and a considerable number of cable faults are caused by the negative effects of frequent DC withstand voltage tests. Therefore, it is widely recommended by relevant departments at home and abroad to replace the traditional DC withstand voltage with AC withstand voltage.