Greater Gabbard OFTO ‘could not have forseen’ seal failure that released SF6

Ofgem has agreed to give extra availability credit to Greater Gabbard OFTO plc, the company that owns and operates the cable that connects the Greater Gabbard offshore wind farm with the onshore network. The regulator agreed that a reduction in cable availability between 24 August and 26 August last year was required by an ‘exceptional event’ that could not be forseen by the OFTO.
The OFTO had to reduce availability to repair a leaking cable sealing end (CSE). The CSE was supposed to require no maintenance, but in fact insulating material that it contained, sulphur hexafluoride (SF6) gas, had been released because of a failure in the ‘O ring’ seals at the top of the CSE. As a result, oil levels had risen and ulitmately also leaked.
An investigation carried out by EDS HV Limited (the Licensee’s O&M contractor) found a “steady continued incremental rise in [the] oil level since the asset was first put into service”. SF6 use by the industry is under scrutiny as its global warming effect is very high – it is said to be around 24,000 times as damaging as carbon dioxide.
Greater Gabbard OFTO will now have its reported system incentive performance adjusted by 9,643MWh to offset the full duration of the transmission service reduction.
Greater Gabbard has been in operation since 2012 and Greater Gabbard OFTO is owned by Equitix Transmission and Equitix Capital Investors.

Further reading
The worst greenhouse gas: why the electricity industry has to grapple with SF6
SF6 alternative: major suppliers announce collaboration