Discussion on problems of single conductor small corona cage´s design

Corona cage was an important research method to research corona effect. As design corona cage, the distance form cage wall to conductor, critical distance of AC charge, and corona cage length, and these questions should be resolved. Corona onset voltage, breakdown voltages were important coefficients to research conductor corona characteristics, and this was significant for transmission line design. To a certain diameter conductor, the diameter of corona cage should be small enough to make the conductor corona onset at a low voltage. Simultaneously, the gap between cage wall and conductor should be lager enough, so as to make breakdown voltage 50% higher than corona onset voltage. The critical distance of AC charge was calculated, and the length of corona cage was selected. The cross-section side width of the corona cage was 1.8m × 1.8m., and the measurement length of the cage was 3m, both of the protection length were 0.5m respectively. As in test, conductors were placed in at the center of the cage, and corona loss measurement system was adopted to measure conductors corona loss. Corona loss of conductor LGJ-630/45, LGJ-400/35, LGJ-300/40 were measured, and an excellent test effect was obtained.