Underground power-line alternatives

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) Initiative and is promoting the use of HVDC to connect the county.  The Department of energy states “Ultimately, HVDC technology has many benefits for the American grid as  it is cost-effective over long distances. 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,  HVDC systems offer cost savings that outweigh these high converter  costs. These savings include relatively low loss rates and cheaper  construction costs. Over long distances, HVDC losses can be up to 30-50%  lower than comparable HVAC systems, reducing long-term costs. “

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

PJM Recent selected Dominion’s  200 mile all underground HVDC project from the Heritage substation in Southern Virginia to the Mosby Substation in Loudoun County (aka Dominion’s  Commonwealth Energy Express) . Here is Dominion’s HVDC fact sheet,  on page 2 read why it is easier to bury HVDC than HVAC.

Read PJM’s HVDC fact sheet.  Even PJM acknowledges “Still, as a solution for interregional, long-range transmission, HVDC systems have evolved to deliver cost and design advantages over AC high voltage transmission. Uses range from undersea cables to deliver bulk electricity from offshore wind to the coast, or overland HVDC systems to transport renewable solar and wind power located in unpopulated areas to urban areas. HVDC technology can also connect regional grids that operate at different frequencies. There are more than 100 HVDC transmission projects around the world, including lines stretching more than 6,000 miles from northwest China to the coast. In North America, there are several thousand miles of HVDC in operation, according to the U.S. Dept. of Energy.  Between PJM and the New York ISO, several HVDC projects provide service.”

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.

References:

1. DOE Super Electronic Highway Grid Presentation: Modernizing the Grid / HVDC and MTDC
2. Electric Technology:  Difference between HVAC and HVDC
3. Detailed Differences Between HVAC and HVDC
4. 2024: Federation Of American Scientists : Creating a National HVDC Network
5.  2024: DOE HVDC Cost Reduction (CORE) Initiative
6. 2023: DOE  Connecting the Country with HVDC
7. 2023: The Operational and Market Benefits of HVDC to System Operators.
8. 2022: NextGen Highways Feasibility Study for Minnesota Department Of Transportation
9. 2022: NextGen Highways  Buried HVDC is Cost Competitive
10. 2014: ABB Review: Special Report 60 years of HVDC

Workshops:

• Read materials from the December 16, 2025 MISO HVDC Assessment Workshop
• Read materials from the  June 23, 2023 ERCOT EHV and HVDC Workshop

Articles:

• Why are utilities building tomorrow’s grid with yesterday’s technology?
• Merchant Developers fill “void” in US Inter-regional Grid Build-out
• Creating a National HVDC Transmission Network
• Harnessing HVDC transmission as a  transformative force in modern grid design
• Undergrounding: Case Study: Undergrounding to Support Data Center Demand Growth
• Connecting the Country with HVDC
• Cyber Attack Resilient HVDC
• Siemens Energy: HVDC Solutions
• Super Electric Highway Grid Presentation: Modernizing the Grid / Multi – Terminal HVDC
• The HVDC Center: Multi-Terminal HVDC Webinar Series Part1 – Introduction to Multi-terminal HVDC
• IEEE Spectum: HVDC Networks Come To Europe
• Converting existing HVAC transmission corridors to HVDC is an overlooked option for increasing capacity

 Virginia Studies and Proposals

• Dominion 2025  185 mile all underground HVDC backbone proposal
• Black & Veatch 2009 partial underground HVDC study for PATH