Moyle HV Fault Notice

Moyle Interconnector Fault


Over the weekend past a serious operational problem arose with the Moyle Interconnector, the 500MW electrical link between Northern Ireland and Scotland. At 15.25pm on Saturday 18th of February the Southern high voltage cable tripped, indicating a fault with the high voltage conductor.

Initial investigation has indicated that there is a cable fault which is located offshore in water of approximately 140m in depth. The Southern Cable has been disconnected and Moyle is now operating at a reduced capacity of 250MW.

Further investigation is continuing in order to pinpoint the precise location of the fault and to establish the cause of the problem.

This is very much an unexpected event in that the fault relates to the high voltage element of the interconnector which is robust and well established technology. It is regularly tested, passing all tests, and has operated without any problems since installation over 15 years ago. The other elements of the Moyle Interconnector, including the new Metallic Return Conductors which were successfully installed last year are unaffected and continue to perform in line with expectations.

It is too early to say if the cable has been damaged on the seabed following some kind of strike or if there is some other reason for the fault.

While investigations continue, Mutual Energy will begin to source the resources (specialist vessel, equipment and repair teams etc) necessary to deliver a full marine repair. Depending on the availability of resources and the nature of the seabed a sea-based repair could typically take an estimated six months.

This fault does not affect the ability of the interconnector Northern cable to continue to contribute 250MW to Northern Ireland’s electricity system.


Mutual Energy Limited – 20 February, 2017

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