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Press Release - 7th July 2011

On 26th June 2011 at 0417 a fault was recorded on one of two 250 MW cables that comprises the Moyle electricity interconnector, which connects the electricity systems of Northern Ireland and Scotland. As a result, the Interconnector’s capacity for the transfer of electricity between Scotland and Northern Ireland has been halved. The fault has been confirmed as a short circuit between the integrated return conductor and earth. Testing has shown the fault to be located offshore, approximately 17km from the Northern Ireland shoreline in a water depth of 140m. Further testing will be required to back up these initial findings and provide a more precise indication as to the location of the fault. These further tests may involve a short outage on the second cable (Moyle pole 2).

The repair process will involve cutting the cable through, de-burying enough cable to allow the ends to be lifted to the surface, removing the defective length then re-jointing in a new section of cable with two full joints and enough new cable that will form a loop on the seabed when the cable is re-laid. A repair schedule is currently being devised with the critical path being sourcing an appropriate vessel to carry out the repair, and fitting it out with the necessary equipment. At present, it is estimated that a 3-6 month timeframe for the repair is likely.

For the period when only half of Moyle’s capacity is available the system operator SONI has to consider alternative means of providing back up to the system. Electricity suppliers in Ireland also have a reduced access to potentially cheaper power in the GB market. The owners and operators of the Moyle Interconnector, Mutual Energy Limited (MEL), are therefore liaising directly with specialist engineers to identify and repair the fault and get full capacity restored as soon as possible.

For the duration of the fault MEL will continue to auction the full capacity of Moyle (ie 410 MW summer import capacity) and then reduce capacity holdings and rebate capacity charges on a pro rata basis.

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Notes for editors:

1. The Moyle Interconnector consists of two separate 250 megawatt (MW) cables running 63 kilometres between converter stations in Northern Ireland and Scotland. Moyle has a capacity of 500 MW but is limited to the transfer of 450 MW from Scotland to Northern Ireland and 294 MW from Northern Ireland to Scotland.

2. For further information contact:
Owen McQuade, Lagan Consulting
Tel: 028 9261 9550 / Mob: 07967 094494