HVDC TRANSMISSION SCHEMES

The present invention provides a high voltage direct current (HVDC) transmission system () comprising: a first station () comprising series-connected first and second HVDC converters (); a second station () comprising series-connected third and fourth HVDC converters (), wherein a neutral node () coupling the third HVDC converter () to the fourth HVDC converter () is coupled to earth; a first transmission line () connecting a positive node () of the first HVDC converter () to a corresponding positive node () of the third HVDC converter (), wherein a first pole () of the system () comprises the first HVDC converter (), the third HVDC converter () and the first transmission line (); a second transmission line () connecting a negative node () of the second HVDC converter () to a corresponding negative node () of the fourth HVDC converter (), wherein a second pole () of the system () comprises the second HVDC converter (), the fourth HVDC converter () and the second transmission line (); characterised in that: a neutral node () connecting the first HVDC converter () to the second HVDC converter () is coupled to a parallel combination of a resistance () and a neutral bus ground switch () for coupling the neutral node () to earth.