On 28 October 2014 SSE agreed an initial one-year contract with the National Grid to provide, through the recently introduced Supplemental Balancing Reserve (SBR) service, backup reserve of up to 780MW of capacity from its Peterhead power station in Aberdeenshire.
Following contract signature SSE requested that the station be allowed to carry out a one-off ‘non proving run’, as permitted under the terms of its SBR contract. The ‘non proving run’, which was not linked to the formal SBR ‘proving test’ process, was designed to allow SSE to test Peterhead’s technical capabilities after eight months of the station not being fully operational.
On Wednesday 5th November Peterhead successfully carried out this one-off ‘non-proving’ run, which was approved and facilitated by National Grid. The plant generated throughout the day, gradually increasing its output until the evening peak period when it generated at 740MW for just over two hours.
On Thursday 20 November, in accordance with the terms of the SBR contract, National Grid called Peterhead onto the system at four hours’ notice to carry out a ‘proving test’. National Grid carries out these short notice proving tests to formally test whether generators can respond as required by their SBR contracts. These tests also enable stations to identify any areas in which performance needs to be improved.
Peterhead has three operational gas-fired turbines which generate electricity at the station, with any two required to meet the SBR contract requirements. At the time it was called on Thursday 20 November one of these turbines, GT12, was undergoing repair work to fix a minor electrical problem identified during the non-proving run. The turbine was therefore unavailable to generate. The other two turbines, GT’s 11 and 13, were both available.
During the proving test GT13 generated successfully. However GT11 experienced technical difficulties meaning it was unable to generate. GT13 could have continued to operate throughout the day at a maximum output of 160MW, but SSE agreed with National Grid to stop all generation at 14.00. This was in order to reduce the costs incurred by National Grid for calling SBR contracted plant and so that the technical difficulties could be investigated.
Further investigation revealed a minor electrical issue with GT11. This was unrelated to the electrical problem identified at GT12. Both issues were rectified earlier this week, and both turbines were returned to service and made available to National Grid on Tuesday 25 November.
Under the rules of SBR, any station which fails a proving test will be re-tested by National Grid. Peterhead was called onto the system today (Thursday 27 November) to undertake this re-test, which it has completed successfully.