Electricity distribution and related services

Tender description

The authority would like to make known its intention to seek expressions of interest from the market with regards to a potential requirement to procure services to deliver a ride through standby service for the 33 kV distribution system on Shetland post any connection of the 33 kV distribution system to a new 132 kV transmission system supplied via a high capacity HVDC link between Shetland and the national electricity transmission system. The service will maintain an uninterrupted supply to all consumers and generators connected to the 33 kV distribution system when the single circuit HVDC link or associated transmission network infrastructure suffers an unexpected forced outage. The authority would like to make known its intention to seek expressions of interest from the market with regards to a potential requirement to procure services to deliver a ride through standby service for the 33 kV distribution system on Shetland post any connection of the 33 kV distribution system to a new 132 kV transmission system supplied via a high capacity HVDC link between Shetland and the national electricity transmission system. The service will maintain an uninterrupted supply to all consumers and generators connected to the 33 kV distribution system when the single circuit HVDC link or associated transmission network infrastructure suffers an unexpected forced outage. It is a condition of the authority’s operating licence that it provides consumers on Shetland with an enduring power supply. Therefore, it will be procuring any necessary equipment and services directly through bespoke arrangements. The authority has undertaken preliminary dynamic modelling of the transients following an unexpected forced outage on the HVDC link and the 132 kV connection to the HVDC link and it intends to put in place a ride through standby service comprising the following: — a standby power station which is able to start within 30 minutes and deliver firm available power and energy for a continuous unlimited period as a standby in the event that the HVDC link suffers a prolonged forced outage. It is currently anticipated that the existing generating station will provide the standby power station service until the end of its economic life when it will be replaced. This is expected to be sufficiently far into the future that this element of the service is considered out of scope for the purposes of this opportunity, — a 55 MW (at least 25 MWh) energy storage system connected to the 33 kV distribution system which provides power and energy very rapidly following a disconnection of the HVDC link and for approximately 30 minutes whilst the standby power station starts up. Once the power station has started and the Shetland 33 kV system is operated as an island the energy storage system will provide balancing and frequency management services, — a 20 MVA synchronous compensator augmented with a flywheel for additional inertia connected to the 33 kV distribution system. Detailed modelling will be completed and used to refine the Ride Through Standby Service following any contract award for the construction of the proposed HVDC link to Shetland. The synchronous compensator will be owned and operated by the authority. Vendors of synchronous compensators should provide performance brochures and experience lists for similar equipment connected at high voltage. The authority is expecting to procure the energy storage system via a services type contract agreement commencing in 2025. Payments are envisaged to be a monthly availability payment for readiness services and utilisation payments for balancing and frequency management services with a material incentive scheme such that payments would be significantly reduced for failure to deliver the service. The services provider would be expected to be responsible for the performance of the energy storage system during the life of the contract. The energy storage system may be located on a single site or as a distributed resource to provide additional services to the Authority at key points on the 33 kV network. Provided it does not affect the provision of the contracted services the authority shall not prevent the service provider securing revenue for other services from the energy storage system subject to reasonable limits on any oversizing of the energy storage system. This could include installing the energy storage system prior to 2025 and providing an energy banking type service to address constraints and so increase the amount of electricity generated onto the 33 kV distribution system by wind turbines.