影响525 kV挤包绝缘柔性直流海缆绝缘击穿的制造工艺因素探讨

Discussion on Manufacturing Process Influence Factors of Insulation Breakdown of 525 kV Extruded DC Flexible Submarine Cable

为验证525 kV挤包绝缘柔性直流海缆制造工艺的可靠性,先对525 kV柔性直流海缆进行交流例行试验,然后进行直流VSC负荷循环试验。通过对击穿试样进行解剖分析和相关试验检测,分析海缆制造工序中可能存在的工艺缺陷,以及绝缘中残留的交联副产物对绝缘性能的影响。结果表明:制造工艺没有发现缺陷,能保证交流电缆品质的制造工艺,不一定全部适用于直流电缆生产。交联副产物含量及空间电荷密度在绝缘层中的分布与不连续环形电树枝出现的位置一致,说明交联副产物含量及空间电荷密度在绝缘层中的分布相较于交流电缆,对直流电缆的影响更大。

In order to verify the reliability of manufacturing process of 525 kV DC flexible submarine cable, the AC routine test and DC VSC load cycle test were carried out on the cable. According to the anatomical analysis and detection of the breakdown samples, the possible process defects in the cable manufacturing process and the influence of residual cross-linking by-products on the insulation performance were analyzed. The results show that there is no defect in the manufacturing process. It can guarantee the quality of AC cable but it is not always suitable for DC cable. The contents of cross-linking by-products and the distribution of space charge density in the insulation are consistent with the location of the discontinuous ring electric tree, which indicates that the contents of cross-linking by-products and the distribution of space charge density in the insulation have greater influences on the DC cable compared with the AC cable.