Submarine Return Electrodes vs. Dedicated Metallic Returns: A Comparative Cost/Benefit Analysis

High Voltage Direct Current transmission systems have become increasingly strategic for the efficient and reliable transfer of electrical power over long distances, particularly in submarine applications. The use of return electrodes in HVDC systems can be a valuable choice for providing a low-resistance current path both in Monopolar and Bipolar links, taking advantage of seawater as conductive medium. This solution is generally more cost-effective and has lower electrical losses compared to Dedicated Metallic Return conductors. The purpose of this paper is to provide a comparative cost analysis between a system with submarine electrodes and the same one with a dedicated metallic return. It seeks to identify the break-even point at which submarine electrodes become more advantageous than dedicated metallic returns for a typical 1 GW HVDC submarine link. Additionally, it compares the costs associated with electrical losses between the two solutions both for Bipolar and Monopolar links. Eventually, the paper provides an overview of the potential impact of an offshore electrode on the environment and metallic infrastructure and how it can be mitigated through a scrupulous design and careful site selection.