The Influence of Space Charge on the Insulation Failure of DC Cable and Its Mechanism Study

Flexible DC cable has been more and more extensive research, compared to the AC cable, the effect of space charge on the insulation failure of DC cable is more significant. This paper summarized three methods to improve the space charge of insulating materials, namely: nano-partice modification, grafting special functional group modification and blending modification, the analysis shows that nano-particle modification and grafting special functional group modification method are better than the blending modification method in improving the electrical properties of insulating material. This paper has also discussed mechanism of the three modification methods, the modification of nano-particles and the modification of grafting special functional groups both can form traps in the insulation materials, limit the movement of space charge, but two methods will be affected by the grafting rate and dispersion and these in not good to control in the actual production process. The difference is that the special functional groups will also play the role of charge donor, to increase the space charge. The presence of nano-particle size effect, resulting in easy agglomeration of polymer, and the two modified methods will be further verified in the development process of DC 500kVcable.