AC Conductors' Corona-Loss Calculation and Analysis in Corona Cage

Corona loss generated from conductors is one of the important design factors of extremely high-voltage ultra-high voltage (EHV/UHV) ac transmission lines. The charge simulation method was adopted to calculate conductor corona loss in the corona cage. Every corona cage wall is equivalent to the ground plane and, therefore, the calculation model is more complicated than the power-line model above the ground surface. Two corona cages-UHV corona cage and small corona cage-were adopted in the tests. The cages are both square sections. Single conductors and bundle conductors were tested in the corona cages to verify the corona cage calculation model. And the same type of conductor was tested in the small corona cage and in the UHV corona cage to check the measuring system and the simulation program of corona loss further. Since the artificial rain rates were from 12 to 20 mm/h, corona losses were measured and calculated. The results indicate that the fundamental frequency component is the most main component of corona loss. The corona cage corona-loss calculation model is appropriate. And for single conductor LGJ-500/35 and bundle conductors, 8 LGJ-500/35, under heavy rain conditions, with the rain rate being from 12 to 20 mm/h, the roughness coefficient range is from 0.4 to 0.5 approximately.