Research on corona control in DC voltage withstand test for UHV converter transformer

Corona discharge will influence the partial discharge measurement during direct current (DC) withstand voltage test for ultra high voltage (UHV) converter transformers. This paper discussed the corona control measures for corona ring and foil expansion pipe, through finite element method (FEM) simulation. An 800 kV converter transformer was taken as object. The influences of the size of corona rings and arrangement of foil expansion pipe on their surface electric field intensity during the test were discussed. Maximum surface electric field intensity values under different arrangement are given. The results of this paper can provide some reference to actual test of UHV DC transmission projects.