THE VOLTAGE ENDURANCE CHARACTERISTICS OF HVDC CABLE INSULATION SLICES

The direct current (DC) voltage endurance coefficient n is used to represent the DC voltage endurance characteristic of insulating materials, which is important in structural design and test assessment of DC cable. However, the research on n of HVDC crosslinked polyethylene (XLPE) cable insulation slices at 90 ℃ is rare, and there is a lack of long-term test data to support the design of HVDC cable working at 90℃. Therefore, the actual measurement of DC voltage endurance characteristics of XLPE at 90 ℃ is of great significance. In this paper, the DC voltage endurance characteristics of XLPE insulation slices from the HVDC cable at 90 ℃ are studied. The DC breakdown field strength of XLPE samples at 90 ℃ is obtained by continuous boosting method, and the endurance voltage tests are carried out at 10 different electric strength levels respectively. The result shows that the E-t characteristic curve of XLPE slices is approximately linear in domain I and n=7.34, while the curve tends to become horizontal in domain II and the electrical threshold stress is 95 kV/mm. The electrical aging might be negligible for the HVDC cable wo㼞king at 90 ℃in the long-term operation.