Case Studies

Sellindge 400kV AC-DC Convertor Station

Sellindge 400kV AC-DC Convertor Station

From 2009 through to 2014 Powell Engineering UK Limited (PEL) have worked with Alstom Grid to completly renovate the UK end of the world’s highest rated submarine High Voltage Direct Current link with France.

The original 400,000 Volt interconnection consisted of plant and equipment designed specifically for this facility being the only one of its kind in the world and consists of two 1,000 Mega Watt Bipoles providing an impressive 2,000 Mega Watt capacity of power transfer.


What we were Asked to Do

PEL were challenged with the complete dismantlement and replacement of the existing equipment in two distinct phases, allowing one Bipole to remain in service maintaining an operational link with France. In addition, PEL were asked to complete each of the two Bipole refurbishment installations in just 28 days.

This extremely demanding timescale required PEL to analyse and meticulously plan every operation, innovating techniques to minimise the time for every operation in order to meet these extremely tight deadlines.


How we did it

The key to our success was both efficiency and safety, delivering value to our client. Existing valve module dismantlement methods proved to take too long given the short timescales, so PEL designed and developed new equipment to speedily remove the 1,000 valve modules from the stacks. Cutting edge compact cranes were employed to operate in the confined Valve Halls. Both day and night shifts worked tirelessly to a detailed integrated programme comprising a diverse range of engineering disciplines including structural and mechanical design, cooling and HVAC system installation, control panel, wiring and cable installation together with new floor mounted HVDC thyristor valve installation. In excess of 200,000 man-hours were worked by PEL with only one injury, reflecting an outstanding safety performance.

What Delivered the Success

Genuine operational teamwork together with a relentless determination to overcome every difficulty and challenge proved to deliver our goal. We forged a professional and cooperative relationship based on trust and commitment with both Alstom our client and the end user National Grid.

Being prepared to do more than that ordinarily expected, secured the success in PEL meeting the challenging programme deadlines for the project. Phase 1 Outage for Bipole 1 was completed in May 2011 followed by the conclusion of Phase 2, Bipole 2 in May 2012.

The meticulous detailed knowledge and cooperation from Tim Brooker’s team on site together with the leadership from Stephen Mart of National Grid and Alstom was critical to the completion of the project and the management of the refurbishment works whilst maintaining an operational Bipole throughout.

In addition, PEL provided important support with the cabling installation at Les Mandarins in order to expedite overall completion of the refurbishment.


On Reflection

The experience of the Phase 1 works proved to be invaluable in the preparation for the Phase 2 operation. Refined waste removal methods and installation programming together with an optimised management structure demonstrated an even higher level of operational efficiency through Phase 2 of the works.

The combined dedication from everyone at National Grid, Alstom and Powell Engineering UK Ltd., delivered the refurbishment of the Sellindge Converter Station safely and successfully.