Corona onset characteristics of grading rings on ± 800kV UHVDC transmission line

Corona discharge phenomenon ought to be considered as a key technical problem during the design, construction and operation of UHVDC transmission line. As indispensable and important attachments, research on fittings´ corona is a significant issue to electromagnetic environment (EME) of DC transmission project. Fittings´ surface field strength provides basis of its corona experiment to test its discharge voltage. It would also provides reference about size design and standardized test of fittings. According to few studies over the past decades, this paper presents corona test set-up plan of grading rings on + 800kV UHVDC transmission line to simulate actual situation. Based on Ansoft FEM calculation software, it proposes comparison of surface field strength and its distribution under actual operation and experiment arrangement. Corona onset voltage of specific grading rings is tested. The analysis among theoretical study, simulation and experiment indicates that the onset voltage calculated by Peek´s formula is higher than experimental results. Peek´s result should be further discussed about the applicability to large-size electrode.