TransBay Cable

In September 2007, TransBay Cable, LLC, hired Siemens to supply two converter stations for a new submarine high-voltage direct current (HVDC) transmission link that would run from Pittsburg, California to San Francisco, California. Siemens chose Cupertino Electric as the project’s electrical contractor to construct the very first HVDC PLUS project in the world using the Siemens HVDC PLUS and Prysmian XLPE HVDC cable systems. The project was the first of its kind in the world, using a multi-level VSC converter system. 

The DC cables are buried in a safe corridor beneath the San Francisco Bay and away from existing AC cables. This critical power transmission infrastructure project is capable of providing more than 40% of the power needs for the City of San Francisco. 

Cupertino Electric served as prime contractor on the project and installed the AC and DC yards at the Pittsburg and San Francisco sites, the reactor yards, the transformers and the converter hall, as well as provided and installed all structural steel, bus work and insulators. 

CEI's scope of work included: 

• Procuring and installing all copper and fiber control cables for the converter hall
• Installing 0.6-mile underground AC cable connecting the Pittsburg PG&E power plant to 400 MW
• Erecting and installing the converter module (power module) 
• Installing the 230 kV AC substation yard, 115 kV AC substation yard, 200 kV +/- DC yard
• Laying underground AC cable  
• Installing all cable raceways, the high voltage bus system and 2,580 power modules (IGBTs) at both the Pittsburg and San Francisco sites

Following the completion of the project, Cupertino Electric has served in a consulting role to provide additional post-construction maintenance and operations services at the site.