The studied sending-terminal's UHVDC converter transformer with the UHVAC grid is currently one of the largest-capacity converter transformers

which is characterized by strong support for the large-scale grid power delivering out

strengthening grid's fault tolerance and backup capability

improving grid operation's flexibility and security

lowering the short-circuit currents. The proposed single-active-part converter transformer structure is well-designed

including the single-phase five-leg iron core

the special winding arrangement

the special structure of the spacers and angle rings

and so on

which is a smaller footprint

easier to install and test on site

but is more challenging in the structural design due to the critical railway transportation limitations on aspects of both size and weight. The feasibility of the proposed structure schema is verified by a series of tests

concerning the wave process

the short circuit force

the temperature field

the main insulation

and so on. Among them

the main insulation's electric fields at the import positions are verified to be reasonable

including the AC impressed voltage test

the DC impressed voltage test

and the polarity reversal test. It shows that the proposed single-active-part design scheme is practicable and conductive to manufacture and application for the UHV large-capacity converter transformers.