Maximum protection for international HVDC connection
The high-voltage direct current connection "Nemo Link" is intended to ensure that the power grid of GB is connected with the Belgian grid. It is a 140 km long connection via an undersea cable across the North Sea. The objective of the project is to provide increased energy security for both countries. Secondly the NEMO Link is designed to encourage the integration of renewable energies into the European energy system. With this international power exchange, the variability of regional production can be smoothed out.
Bi-directional HVDC undersea connection
The end point in Belgium is the industrial area of Herdersbrug, a district of Bruges. On the UK side, the connection terminates on the site of Richborough power station, which was decommissioned and demolished in 2012, near the town of Sandwich in Kent. The backbone of the transmission system is two undersea cables, which operate in a symmetrical monopole configuration, each at a high voltage potential with respect to ground in opposite polarity, with a DC voltage of ± 400 kV. The maximum transmission power is 1 GW. The design and supply of the power converter stations and transformers required for its operation were supplied by a consortium of Siemens AG (Germany), Siemens Transmission and Distribution Ltd (Manchester, UK) and Siemens Belgium.
Experienced industrial partner
To secure the system against grid disturbances or failures, Siemens looked for a partner with appropriate experience of supplying highly reliable power supplies and UPS systems into industrial applications. Consequently in August 2016 an inquiry was sent to BENNING, who have a long-standing successful global partnership with Siemens and who had demonstrated their low risk and reliability as a supplier through their excellent support in the Western Link HVDC project.
The design phase was completed between August 2016 and February 2017, where the final system design and commercial terms were agreed. A technically compliant and highly reliable solution with a long service life and low total cost of ownership was developed in accordance to the individual requirements and requested specifications of the customer. In February 2017 Siemens placed an order for the manufacture of the desired dual power supplies and UPS systems.
The structure of the system designed by Siemens and implemented by BENNING is 2n + 1 redundant.
Two industrial UPS systems of the ENERTRONIC I 3-3 series are used (160 kVA / 384 V DC bus voltage), two modular rectifier systems in n + 1 redundancy design (each based on five modules of the type TEBECHOP 13500 SE / 110 A) and two industrial inverters of the type INVERTRONIC I (15 kVA). In addition, there are two battery banks which can supply the loads with electricity for a maximum bridging time of six hours. The redundant system design guarantees maximum availability of all connected critical loads.
The rectifier and inverter systems are used to supply the control and safety systems on site. At the same time, the UPS systems secure the motors of the HVDC converter water cooling system against a power failure and bridges the period until the back-up diesel generator has started up.
The UPS bypass transformer is specifically designed to cope with the high currents produced when starting the motors. If a failure of the UPS system occurred here, the water cooling system would also fail. A total failure of the power supply system would lead to the site systems being unavailable which would lead to an interruption of the HVDC connection.
Permanent customer contact
The entire production period was 21 weeks. The delivery at the Belgian location took place in July 2017, and at the British site in November 2017. BENNING UK was responsible for managing the project, working in support of Siemens in Manchester.
BENNING UK was in constant personal contact with the customer, which has always been the central basis for building successful relationships within BENNING group.
The power supply system was commissioned in August 2018 and in the meantime the commissioning of the entire HVDC system has also been completed.
Other HVDC projects
In addition, BENNING was awarded the contract for the power supply systems for Cobracable HVDC link, an interconnector between the Netherlands and Denmark, Aachen Liège Electricity Grid Overlay (ALEGrO) the first electricity interconnector between Germany and Belgium as well as Eleclink HVDC Link which will connect the power grids of France and Great Britain through the operational tunnel of Eurotunnel.
"We see this as confirmation of our professional work and as an incentive for future projects," says David Whitlow, Managing Director at BENNING UK.
Efficient transfer – maximum reliability
Together with HVDC Plus technology from Siemens, the BENNING power supplies and UPS systems ensure the permanent and efficient transfer of electricity over a distance of about 140 kilometres. Both companies therefore make a significant contribution to sustaining an undisrupted supply of power to European households on both sides of the Channel as reliably as possible.
author/contact: David Whitlow
telephone: +44 118 973 1506