中国首根±525 kV XLPE绝缘直流电缆的设计与试验验证

Design and Test Verification of China's First ± 525 kV XLPE Insulated DC Cable

介绍了中国首根±525 kV交联聚乙烯绝缘直流电缆的研制与试验情况。采用阻水带作为填充材料设计了3 000 mm^2型线阻水铜导体,通过计算导体填充系数可达95.5%,纵向透水试验结果表明,该导体在2 MPa水压作用下10 d后的透水距离为7.2 m,在1 m水柱作用下经受10次热循环后的透水距离为0.9 m。该直流电缆选用铜丝绞合作为金属屏蔽层,在铜丝内同时植入两根光纤单元,满足光纤通信和在线测温的要求;铝塑复合带与聚乙烯护套构成综合防水层,电缆整体外径比同规格皱纹铝套结构减小10%。为了验证±525 kV直流电缆的电气性能,进行了交流525 kV下的耐压和局部放电试验,并送国家电线电缆质量监督检验中心参照CIGRE TB496—2012和GB/T 31489.1—2015进行全性能型式试验,如复合循环、直流耐压、叠加冲击等并全部通过,负荷循环试验过程中导体最高温度大于70℃、绝缘层最大温差大于30℃。

The development and test of China's first±525 kV crosslinked polyethylene(XLPE)DC cable are introduced.A type of heteromorphic copper conductor with a section of 3 000 mm2 was designed,and a waterblocking tape was chosen as filler material.After calculation,the filling factor of the conductor reached 955%.Longitudinally permeability tests on the insulated conductor have proceeded under the condition of 2 MPa hydraulic pressure for 10 d and 1 m water column with thermal cycling for 10 times,the length of permeability was 72 m and 09 m respectively.Copper wires were twisted as a metallic shield of the±525 kV XLPE DC cable,among the copper wires,two optical fibers were implanted in to achieve the requirements of communication and thermometry online.A composite waterproof sheath was compounded with aluminumplastic tape and PE,hence,the outer diameter of cable has been minished 10%compared to corrugated aluminumsheathed cable in the same voltage and section.To verify its electrical properties,voltage test and partial discharge test under AC 525 kV were carried out,then a whole performance type test was taken in National Center of Testing and inspection for Electric Cable and Wire(TICW)referred to CIGRE TB496-2012 and GB/T 314891-2015,including load cycle test,DC withstand voltage test,superimposed impulse test and so on,and the conductor passed all the tests.During the load cycle test,the maximum temperature of the conductor was over 70℃,and the temperature gradient in insulation exceeded 30℃.