Scottish Hydro Electric Power Distribution (SHEPD) is preparing to begin work next week to install a new electricity cable between Lerwick and Bressay which will run through a duct bored below the seabed, in a first for inter-island cables in the UK.

Specialist contractor Stockton Drilling will bore and line a 20 centimetre duct that will run horizontally across a distance of just over 500 metres, beneath the north mouth of Lerwick Harbour at a depth of more than 15 metres below the seabed.

Most existing power cables serving island communities around the UK are laid directly on the seabed where their position is highlighted via markers on the shore, charts and navigation systems. According to SHEPD, the new method, which could be used in the future on other suitable short cable crossings, reduces risk of damage to the cable, brings safety benefits and enables faster, lower cost replacement of the cable when required.

The use of this technology for the replacement of one of the two existing 11 kilovolt cables which connects Bressay with the hub of Shetland’s electricity network at Gremista follows the development by SHEPD of a new framework to assess the costs and benefits of different approaches to installing, protecting and maintaining its submarine cables.

SHEPD investment manager Adam Bain said:

“Submarine distribution cables play a critical role for our customers, particularly by providing a lifeline service to 59 island communities around the north and west of Scotland. Last year, we carried out a review of the way we manage these links and sought feedback to make sure we are able to identify the right approach in every case. To achieve the best solution for our customers, we need to take account of the specific conditions at every location, the risk of conflict with other users of the seabed and the need to ensure that the costs passed on to energy consumers are justified.

“For Bressay, this review identified the opportunity to take advantage of improving technology by extending the application of a method that has been used before for road, railway and river crossings. The result should be an improved power supply for customers in Bressay and a saving for bill-payers across the north of Scotland over the lifetime of the cable duct.

“We don’t anticipate any impact on customers’ power supplies while the work takes place. The drilling itself is expected to cause minimal disruption beyond the temporary compounds and access arrangements which will be in place at either side of the crossing from next week. Installation should be completed by the end of June and the duct created should serve customers for decades to come.”

Source: SSE