The failure of the high voltage undersea cable between west Scotland and north Wales last month resulted in National Grid ESO paying almost £31m for wind farm operators to curtail output.
Consultancy Cornwall Insight calculated the figure based on Balancing Mechanism data and prices during what was an exceptionally windy month.
The Western Link HVDC cable went down on 10 January and remained offline until 8 February. It was the cable’s third complete trip in as many years.
Cornwall Insight’s graph shows the volume of wind bids (instructions to reduce output) accepted in the BM classified as system actions (constraints) hit a record high of 429.8GWh in January.
“The Western Link was designed to accommodate the increasingly high volume of power generated in Scotland and prevent transmission bottlenecks. But since commissioning the cable has been fraught with issues,” said analyst Lee Drummee.
“The availability of the link makes a clear difference. For example, December 2019 also saw high wind output of 5.6TWh. However, the Western Link was available in December, so, the volume of wind bids classified as system actions on the BM was significantly lower at 247.1GWh.
“Avoiding constraints not only allows more volumes of renewable power to flow onto the Grid but reduces the amount of money that National Grid has to pay to turn off wind farms in Scotland. However, the reliability of the Western Link will need to be solved for its full potential to be realised.
“As more onshore wind develops, especially in Scotland, the problems of constraints will need to continue to be actively managed.”
Following the latest outage, Ofgem has opened a probe into the £1.3billion Western HVDC connector, which links Highland wind farms via Hunterston to North Wales.
Planned to open in 2015 at 2.2GW capacity, the link arrived two years late in December 2017, and then only at 900 MW. Cable problems at manufacturer Prysmian were blamed.
Scottish Power and National Grid took over operations in 2018, and full power was reached only in October that year. Further outages included five weeks in spring 2019.
The regulator’s probe will focus on performance of both operators.