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  • Keeping the power flowing on Shetland

  • Shetland is not connected to the main GB electricity network, which means the islands rely entirely on local sources of generation for their power; in addition, the supply and demand of electricity must be balanced locally.

    As the Distribution Network Operator for the north of Scotland, we own and operate the 33 kilovolt (kV) and 11kV networks on Shetland, which are made up of approximately 1,650km of overhead lines and underground cables operating at distribution voltages (33kV and below). Thirteen subsea cables connect the smaller islands to the main island. There are no overhead lines or underground cables operating at transmission voltages (132kV and above) on Shetland.  

    During the introduction of the British Electricity Trading and Transmission Arrangements (BETTA) of 2005, it was formally agreed that we would also administer electricity generation as well as network operation on Shetland, although we had been fulfilling this role for some time before this.  

    This means that, as we are responsible for balancing the islands’ supply and demand, we are also the System Operator (SO) on Shetland.

    Existing arrangements

    Most of Shetland’s electricity is currently supplied by two fossil-fuel power stations, with the remainder being supplied by wind generators.  

    Shetland’s main electricity generation sources are:  
     
    Lerwick Power Station (LPS) - a 72.8MW diesel-fired station that provides around 50% of Shetland’s electricity on an annual basis.  We’ve recently installed a new engine and 8MW battery to supplement the existing station, and to further increase the amount of renewable generation which can be accommodated on the network. 

    The station was built in 1953 and is approaching the end of its scheduled full-duty operational life, however the station is still very much a part of our future plans, which you can read about here and also further down the page in the “Standby Proposals” section.

    Sullom Voe Terminal (SVT) Power Station - an independently owned gas-fired power station, which meets around 30% of Shetland’s demand. The station’s primary purpose is to supply electricity to the Sullom Voe gas terminal, but it also provides power to the Shetland system through a contractual arrangement. 

    Renewables - a number of small independent and community-based renewable generators, including wind and tidal, which currently contribute around 20% of the islands’ electricity supply.  
    Most of these generators are managed by the Shetland Active Network Management (ANM) system, which originated in an innovative trial project developed by SSEN in partnership with third parties called the Northern Isles New Energy Solution (NINES).   

    The ANM aims to increase renewable generation output and reduce reliance on fossil fuels on the island network, taking advantage of the above-average wind conditions that Shetland experiences. 

    Looking to the future

    Gremista Grid Supply Point

    Electricity is currently distributed on Shetland via our 33kV distribution network.  

    Once the Shetland Islands are connected to mainland GB via the new High Voltage Direct Current (HVDC) subsea cable and the new onshore 132kV network currently under construction by SSEN Transmission, the distribution and transmission networks will need to be connected at a new substation – this is what is known as a Grid Supply Point (GSP). 

    We are working jointly with SSEN Transmission to develop and construct the new GSP.  

    Land close to the existing Lerwick Power Station (LPS) has been identified as a suitable location and initial surveys and designs have been completed.

    Selecting the GSP site

    In conjunction with SSEN Transmission, we initially focused on the LPS site as the intended location for the GSP. After detailed analysis, considering SSEN Transmission’s requirements for the site in terms of scale and other pre-requisites, this option was determined not to be feasible, and alternative land options were identified for assessment.

    We both reviewed alternative land options in detail, brought in consultants to carry out site walk overs and carry out civil engineering desktop assessments, reviewed Local Development Plans, engaged with landowners and other stakeholders including Shetland Islands Council, and held site selection workshops to assess all relevant aspects of the identified areas. 

    After several months of following this process, the preferred site was selected. 

    More details on the site, including a location plan and a red line boundary can be found on pages 7-8 in the consultation booklet, linked in our “Project documents” section.

    Keeping the power flowing - standby proposals

    While the transmission system will supply Shetland’s demand needs for the vast majority of the time, a standby solution is also required to ensure homes and businesses continue to receive the power they need during transmission system outages.

    We have been reviewing options for a reliable, innovative and cost-effective backup solution to support the security of supply to Shetland once the islands are connected to the mainland GB electricity system via SSEN Transmission’s 600MW HVDC transmission link. 

    After extensive technical and commercial analysis of options available, we submitted our proposal on back-up arrangements to Ofgem in December 2020. 

    Following subsequent engagement with the regulator, we’ve included our proposals as part of our business plan for the RIIO-ED2 price control period. 

    More detail on these proposals, including FAQ, can be found on page 4 of our consultation booklet which is linked in our ‘Project documents’ section.