ECS Intranet:
Subsea HVDC connections

Although HVDC subsea cable links have been built since the mid-1950s, liberalisation of energy markets and the construction of larger windfarms further offshore has led to a rapid increase in the number of operational HVDC connections in recent years. Throughout this long history both cable technology and convertor station technology have evolved many times; leading to longer higher power connections for energy trading and also more moderately sized links to improve security of supply to islands.

Supported by the HubNet programme , the Tony Davies High Voltage Laboratory has reviewed HVDC subsea cable projects commissioned since the 1950s. We have also considered projects currently in construction or planning phases, and more speculative future connections. Our work has reviewed the use of sea returns as an enabler to simpler cheaper subsea cable projects. Sea returns have been used since the earliest links were commissioned and are a particularly attractive solution for long distance connections. Our work has focussed on the evidence for any potential environmental impact from sea returns.

The following tables are correct to the best of our knowledge as of the end of 2016: we acknowledge the previous work of David Balloch (EnviroGulf Consulting). The tables may be copied and used for educational/non-profit purposes, and referenced as “TDHVL HubNet Review of Sea Returns (2016)”. The information is presented in the following form:

• A list of decommissioned and currently operational subsea HVDC cable links
• A list of proposed projects, including those in construction and planning and more speculative proposed projects
• Details of HVDC subea links with sea returns

Papers:

• Position paper on High Voltage Direct Current subsea cable electrical return path schemes: Use of sea electrodes and analysis of environmental impact
• Energy Journal paper