High Voltage Direct Current (HVDC) transmission lines use direct current as opposed to the alternating current which is used by the HVAC transmission lines. HVDC is used for bulk transfer of electricity across long distances and for direct point to point applications. Recently, it has begun to be used for shorter distances. HVDC voltages are in the 100kV to 800 kV range.
In comparison to HVAC, HVDC is more efficient and has 30 - 50% less line losses over long distances than HVAC. HVDC transmission lines do not require substations like HVAC transmission systems do, instead an HVDC converter substation is needed at each end of the transmission line. An added benefit is that HVDC lines do not emit EMFs.
In a typical overhead transmission line installation, HVDC uses a narrower right of way and smaller towers. Additionally HVDC cable can be more easily buried than HVAC and can be installed under water.
The trench for the SSO Green HVDC Link (350-mile 2,100 MW, 525KV underground high voltage direct current (HVDC) ) is 3' wide by 5' deep.
When comparing costs between HVDC and HVAC a 2022 feasibility study done by NextGen Highways found that buried HVDC is cost competitive to HVAC. The DOE notes that " converter stations required for HVDC deployment are expensive, however, with a breakeven distance of approximately 37 miles for submarine lines and 124 miles for overhead lines "
The Brattle Group's 2023 report "The Operational and Market Benefits of HVDC To System Operators": "European grid operators in particular have taken advantage of advanced VSC capabilities. Internationally, VSC-based HVDC technology has become the dominant HVDC choice over the last 5–10 years, with approximately 50 GW of VSC-based HVDC transmission projects in operation today and approximately 130 GW planned or under development through the end of the decade. North America accounts for only 3% of all VSC-based HVDC systems in operation worldwide and—almost exclusively due to efforts by merchant transmission developers—for approximately 30% of planned and proposed VSC systems."
In this report they list over 20 case studies.
The U.S Department Of Energy even has an HVDC Cost Reduction (CORE) Initative
Black & Veatch did a study for the PATH 765kV transmission line, that proved HVDC underground was a feasible solution. The full title of that study was : Black & Veatch, "PJM Interconnection Potomac-Appalachian Transmission Highline (PATH) Project, HVDC Conceptual Study, B&V Project No.164996, B&V File 42.2004 , FINAL November 17, 2009 This was entered into the record as part of the Virginia SCC Case PUE 2009-00043 Application of PATH Allegheny Virginia Transmission Corporation
FirstEnergy is now responsible for two massive transmission lines targeted through our communities (Valley Link and MARL/Gore-Doubs-Goose Creek). Its time to re-evaluate and look at ONE single solution - figure out how much power can be reasonably imported from West Virginia and build A SINGLE INCLUSIVE HVDC Underground solution to solve it.
