Project: TransBay Cable VSC

Service: VSC HVDC

Client: Babcock and Brown

Country: USA

Year: 2008-2010


The TransBay Cable (TBC) is the world’s first in-service MMC VSC. It is +/-200 kV 400 MW point-to-point symmetrical monopole VSC link using multi-level converter technology. The TransBay cable connects Pittsburg converter station to Potrero converter station near San Francisco via submarine cable. TGS was the Owner’s Engineer for TBC from day one through to in-service. TGS gained invaluable experience through design review, witnessing factory tests and commissioning of the first MMC VSC installation in the world. TGS Owner’s Engineer services:

  • Economic assessment
  • Review of HVDC manufacturer design reports
  • Witnessing factory performance and type testing
    • Converter valves
    • Control & protection factory performance tests
    • Modules fire resistance tests
  • Commissioning
    • Sub-system testing
    • System testing


  • The first VSC with MMC technology
  • Design verification was not against any existing technology
  • Valve type testing without prior reference technology
  • New concepts in control and protection