Western Link outage and high wind sees constraint cost hit a record high

The Western Link HVDC suffered an unplanned outage on 10 January, which caused it to remain offline until 8 February. This coincided with record-high levels of wind generation in GB with generation from transmission connected wind topping 6.3TWh. However, with 2.2GW of HVDC capacity unavailable, significant volumes of wind output had to be constrained.

Due to this, the cost of turning down wind output through the Balancing Mechanism (BM) hit a record high of £30.9mn*. The graph below 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.

A graph showing wind bid volumes (system flagged) & cost by month of the Western Link

Lee Drummee, Analyst at Cornwall Insight, said:

“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.

“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.”


Notes to Editors

*These costs have been calculated by multiplying the £/MWh bid payment requested by the wind generators for turning down with the MWh volume of such actions.