HVDC advantages pertain irrespective of environment. HVDC only needs one copper conductor. HVDC has no reactive power loss. HVDC has less corona effect and s

HVDC advantages pertain irrespective of environment. HVDC only needs one copper conductor. HVDC has no reactive power loss. HVDC has less corona effect and self-inductance to overcome so conductors can be smaller. HVDC is not subject to grid phase problems. In addition, since HVDC cabling can be cheaper at a given voltage, the voltage can be increased which minimizes resistive losses (Ptrans = IV while Ploss =I^2R--if you double V you halve I which reduces your losses by a factor or 4).