Abstract: A current-modulation method of transmitting high voltage direct current (HVDC) power over a transmission system comprising at least three conductors, wherein each conductor has a nominal thermal limit to its current-carrying capacity. The method involves transmitting DC current over at least one conductor at a level which can exceed each such conductor's nominal thermally-limited current-carrying capacity, returning the transmitted current over a quantity of conductors greater than the quantity used to transmit at the higher level, so that each return current is less than the transmitted current, and periodically switching the current level in the conductors so as to rotate the higher level current among at least two of the conductors, such that, over time, the resistance heating of the conductors does not exceed any conductors' thermal limit.

Abstract: A current-modulation method of transmitting high voltage direct current (HVDC) power over a transmission system comprising at least three conductors, wherein each conductor has a nominal thermal limit to its current-carrying capacity. The method involves transmitting DC current over at least one conductor at a level which can exceed each such conductor's nominal thermally-limited current-carrying capacity, returning the transmitted current over a quantity of conductors greater than the quantity used to transmit at the higher level, so that each return current is less than the transmitted current, and periodically switching the current level in the conductors so as to rotate the higher level current among at least two of the conductors, such that, over time, the resistance heating of the conductors does not exceed any conductors' thermal limit.