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Railroad DC Tie (Sharyland), back-to-back station, USA
Case Study

Railroad DC Tie (Sharyland)

Sharyland Utilities awarded Hitachi Energy a contract to build a second 150 MW back-to-back HVDC interconnection at Mission, Texas, near the border with Mexico


The station Railroad DC Tie station will be completed during 2014. Hitachi Energy delivered the first 150 MW HVDC tie (Sharyland I) at the same location in 2007.

The Sharyland ties enable power exchanges between the Electric Reliability Council of Texas (ERCOT) grid with the Mexican national grid, operated by the Comisión Federal de Electricidad (CFE), and increases power reliability in the Rio Grande Valley. HVDC technology enables bi-directional power flow between both grids, thereby allowing each grid to rely on the other in times of emergencies or peak demand. 

Hitachi Energy designed an HVDC solution that includes a unique black start emergency assistance capability that provides a safe supply of power during a blackout in either AC grid. The solution also acts as a firewall, isolating disturbances and preventing them from spreading. The system is equipped with Hitachi Energy's MACH control and protection system, specifically designed for converters in power applications.

Hitachi Energy is now building a second 150 MW back-to-back HVDC converter station in Mission, Texas, adjacent to the existing site. The two stations, part of the Railroad DC Tie Expansion project, will work in parallel to provide a transmission capacity of up to 300 MW. This will increase the power transfer capacity between Texas and Mexico, secure power supply and increase the reliability of power in the Rio Grande Valley.

Hitachi Energy will design, engineer, supply and install the new station, including high-voltage equipment such as power transformers and thyristor valves.

Main data
Commissioning year: 2014; 2007
Configuration: Back-to-back
Power transmitted: 150 => 300 MW
Application: Interconnecting grids