Study on the Formation of Capacitor Screen Deformation of Dry-type DC Bushing Core and Its Effect on Electric Field Distribution

As one of the bottlenecks of HVDC technology, the high failure rate of dry-type DC bushing seriously restricts the safe and stable operation of HVDC system. During the actual operation, discharges between capacitor screens occur from time to time, in addition to the screen edges, a certain number of breakdown occur in the middle of screens. For this reason, according to the radial section of a real bushing core, the deformation in the middle screens was analyzed, the curing shrinkage deformation model of the dry-type bushing core was established, and the causes were analyzed. Subsequently, to determine the effect of deformation in the middle of the capacitor screen on the distribution of electric field between capacitor screens, a simulation model of electric field with deformation in the middle of screens was established, and the effect of different deformation on the electric field was studied. The results show that the poor local impregnation results in the deformation in the middle of screens toward the center of alumina tube. In addition, the increase of the deformation area's height, and the decrease of thickness of the capacitor screen and the deformation area's width will enhance the electric field distortion.