Siemens has been awarded an order for a high-voltage direct current (HVDC) transmission system to connect the British and Belgian national grids via subsea cable.
Siemens will be responsible for the installation of both converter stations using HVDC Plus technology with a transmission voltage of ±400 kilovolt (kV) DC. The customer is Nemo Link, which is a joint venture between the British grid operator, National Grid, and the Belgian Transmission System Operator, Elia Group. Following completion, Nemo Link will provide 1,000 MW of capacity, enough to power 500,000 households.
The interconnector will run for 140 kilometers between Richborough in Kent and Zeebrugge near the Belgian city of Brugge with a combination of subsea and underground cables. The commercial operation of the link is scheduled for 2019 and the contract includes a service and maintenance agreement for a period of five years.
“We are very pleased to be working with Nemo Link on another landmark HVDC project that will support the integration of the European energy market” said Tim Dawidowsky, CEO of the Transmission Solutions Business Unit within Siemens Energy Management Division.
Mr Dawidowsky added that Siemens has so far installed a total of 4.6 GW of HVDC transmission projects worldwide.
Nemo Link will connect two HVAC electricity systems separated by the North Sea. The utilisation of HVDC avoids the need to synchronise the two interconnected AC networks. Both converter stations will be using HVDC Plus voltage-sourced converters in a modular multilevel converter arrangement (VSC-MMC) that convert AC to DC and DC back to AC on the other side of the link.
The project is one of the European Commission’s ‘projects of common interest’, intended to assist the creation of an integrated European Union energy market. It will also increase energy security in both countries and support the integration of renewable energy, particularly offshore wind. The HVDC Plus system works with power transistors that can be also switched off (IGBT), enabling the commutation processes in the power converter to run independently of the grid voltage. The very fast control and protective intervention capabilities of the power converters provides a high level of stability in the transmission system, which primarily serves to reduce grid faults and disturbances in the three-phase AC network. This significantly increases supply reliability for utility companies and power customers.
HVDC Plus technology enables the efficient transportation of electrical power over large distances and in particular for subsea applications with losses of around two percent, excluding cable losses. It is also highly controllable and brings operational benefits to both transmission systems. The Nemo Link interconnector will allow power to flow in both directions and will be the third electricity connection between UK and Europe. The 1,000-MW-interconnector BritNed between UK and the Netherlands was also developed by Siemens and went into operation in 2011.