An outage at Western Link HVDC has led to record Balancing Mechanism (BM) payments of £30.9 million, according to Cornwall Insight.
During Storm Ciara and Storm Dennis in particular, wind power has surged with generation from transmission-connected wind topping 6.3TWh.
However, with Western Link out from 10 January to 8 February due to an unplanned outage, 2.2GW of capacity was unavailable and a large amount of wind power had to be constrained. This led to the volume of wind bids accepted in the Balancing Mechanism as constraints to hit a record high of 429.8GWh in January.
Lee Drummee, an analyst at Cornwall Insight, said that the Western Link was specifically designed to accommodate the growing capacity in Scotland and stop bottlenecks such as this, but it 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.”
Ofgem launched an investigation in Western Link in January, looking into National Grid and Scottish Power Transmission’s delivery and ongoing operation of the Western HVDC subsea cable. This comes after it has failed six times since it came online.
The £1.3 billion Western Link was originally due to come online in 2015, but only began operating at full capacity in December 2019.
The high cost of balancing the grid given the surge in wind power and the outage comes after The Times reported that in the first six months of 2020, £55.7 million was paid out in constraint payments, while in the whole of 2019 £130 million of constraint payments were made.
Both National Grid and ScottishPower have defended the transmission system, with the latter arguing that “we are confident that our investment in the link has delivered benefits for consumers since entering service in 2017, and will continue to deliver benefits".
“We are committed to providing a reliable link that will transport cleaner greener energy to our homes and businesses across Great Britain," ScottishPower added.
National Grid said that it regularly weighs up the difference between constraint management payments and the cost of building an asset in a “comprehensive cost-benefit analysis". It continued that to date it is cheaper to pay for constraint rather than build new transmission.
A spokesperson for National Grid said: “We use the electricity generation and transmission assets made available to balance supply and demand second by second, always choosing the most efficient mix to keep costs down for consumers.
“The cost of all the services the ESO uses to manage supply and demand across the system is currently £1 of the average annual household bill of £554. The alternative to constraint payments is building more electricity transmission assets which is more costly, meaning consumers’ bills would rise.”
Increasingly National Grid is looking for new sources of constraint management to balance the grid as renewable sources of power in the UK grow. In December, it launched a Constraint Management Pathfinder RFI, in the hope of adding a new service to its operations, and reducing the cost of network constraints.
“As more onshore wind develops, especially in Scotland, the problems of constraints will need to continue to be actively managed,” finished Cornwall Insight's Drummee.