SSEN Distribution is to replace the failed 33kv distribution link to the Isle of Harris on a like for like basis rather than upgrading to a larger link pushed for by some islanders.
The network company said it expected the replacement cable between Skye and the Western Isles off Scotland to deliver 8-10MW more capacity than the current 23.4MW link which failed in October.
Delivery of alternative solutions including replacing the cable with a new 132kv link has been ruled by SSE as delivery would not have been possible before February 2023, leaving Lewis and Harris reliant on a backup diesel generator (pictured) until then and local wind operators constrained without export capacity.
Stornoway Community Council and community wind farm operators had called for a 100MW cable upgrade while the link was replaced to enable new community wind farms to be built ahead of a new interconnector to the islands.
The replacement cable is expected be energised and operational by end August 2021 with the cable arriving in late May.
SSEN Distribution said it worked with SSEN Transmission to undertake a whole system analysis of a range of technical options for the cable replacement and that the decision would limit environmental and community impacts and limit security of supply risks.
The decision to proceed with the replacement 33kV also avoids up to 200,000 tonnes of CO2 emissions from the back-up stations during the timescale projected for larger cable options, it added.
SSEN Distribution director of customer operations Mark Rough said: “Faced with considering replacement options in an emergency scenario, we’ve had to balance the opportunity to progress whole system solutions with the need to restore Lewis and Harris to normal supply and generation conditions in reasonable timescales, limiting impacts where possible.
“We recognise from our engagement with the community there are a range of views about the optimum solution, each with its own trade-offs.
“In exploring options, it became clear that the conditions and timescales related to a larger solution posed a number of challenges which could not be reconciled without leaving customers and network users exposed to significant risk.
“Our priority as distribution network operator remains to ensure a safe and secure supply of electricity to homes and businesses on the islands whilst limiting any risk to supply wherever possible. Today’s decision supports that outcome.”
SSEN said it acknowledged recent calls from some stakeholders for a larger capacity cable to be installed and ringfenced for community renewable schemes, but added that this is not permitted under industry rules and regulations.
Any additional capacity must be allocated in line with the contracted position of developers on a first-come, first-served basis and network operators cannot discriminate between ownership models or technologies, it said
Separately, SSEN Transmission has confirmed that it remains committed to take forward a transmission link to the Western Isles with its progression remaining subject to regulatory approval.
This, in turn, requires sufficient levels of renewable electricity generation on the Western Isles to demonstrate commitment to take projects forward, in line with Ofgem’s expectations.