Integral return and DTS in Moyle HVDC link

Contracts have been placed for the 500 MWe HVDC interconnector between Ireland and Scotland by Moyle lnterconnector Ltd, of Belfast with a view to operating the project in late 2001. The interconnector, which will span a total length of the submarine HVDC link between the two countries of 63 km, is scheduled to enter service in December 2001.

There will be an additional 3 km long underground cable connection from the submarine link to the Northern Irish converter station, and a 5 km underground link link to the Scottish converter station. From the Scottish converter station there is another 60 km of overhead line to the connection with Scottish Power's network. The Northern Ireland converter station is sited directly below the main 275 kV transmission line and is connected directly by droppers.

Moyle Interconnector, a member of the Viridian Group, has been formed to build the interconnector. Total investment in the project amounts to $234 million, of which 35 per cent is being funded by the European Regional Development Fund.

Viridian Group, Northern Ireland's largest company, has three organisational strands – Northern Ireland Electricity (NIE) which is its core business, Viridian Capital and Viridian International. The Viridian Group also includes the business processing outsourcing company Sx3, the Open and Direct financial services company, the Nevada tele.com telecommunications company (which is a joint-venture with Energis), the Zenith property development company, as well as its interests in the power generation field.

NIE also plans to enhance the reestablished 275 kV north-south interconnection between Northern Ireland and the Republic of Ireland and add further 110 kV links. In conjunction with the new hvdc interconnection, this will create a strongly interconnected two-island electricity system.

There will be continuing shortages of power in the Republic of Ireland, peaking in 2001/2002, particularly since two planned new generating station projects have had planning applications turned down on environmental grounds due to intervention by neighbourhood groups.

Siemens has been awarded the converter stations contract for the Moyle link, worth around $100 million. Siemens Power Transmission and Distribution Group in Erlangen is responsible for supplying the converter stations which are located at Auchencrosh in Ayrshire (Scotland) and Ballycronan More in Island Magee, County Antrim (Northern Ireland).

The project provides a vital link in the supply of electricity between Scotland and Northern Ireland, and will enhance both security and competition in the emerging marketplace. The interconnection will help the drive for lower electricity prices in Northern Ireland by increasing competition in generation.

The configuration of the Moyle HVDC interconnector is a dual-monopole system for which each 250 MWe pole is capable of providing bi-directional power transfer. Siemens will be using direct light triggered thyristor valves, which have proved successful at the Celilo Converter Station of the Pacific lntertie in the USA.

This will be the first HVDC cable project in which Alcatel's recently developed submarine power cable with an integral return conductor will be used. The United Kingdom has already had to deal with magnetic field problems and the return conductor solution, which is unaffected by external magnetic fields, was an influential factor in winning the Moyle contract.

Fibre-optics distributed temperature sensing equipment is integrated into the cable system. The fibre optics cable will be manufactured at Alcatel's Rognan factory and will be integrated into the power cable being manufactured in Alcatel's Halden factory in Norway.

The submarine cables, which will be laid by the Norwegian vessel Skagerrak, will be protected against the affect of external mechanical impact by being buried in the seabed over its entire length. The burial will be carried out using the Capjet system that was developed by Alcatel in Norway. This has already been used to bury more than 2000 km of submarine cables and pipeline.