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Chart of the Week


Critical Link: Western HVDC & wind in the BM

Lee Drummee
Lee Drummee

In a previous chart of the week (Bootstrap Bill: Western Link HVDC & BSUoS) in May 2019 we explored the relationship between BSUoS charges and the availability of the Western Link HVDC.

The link suffered a fresh unplanned outage on 10 January, which caused it to remain offline until 8 February. This prompted Ofgem to launch an investigation into National Grid Electricity Transmission and Scottish Power Transmission over the delivery and operation of the cable. In this Chart of the Week we look at the relationship between the link availability and the behaviour of wind in the Balancing Mechanism (BM).

The most recent outage on the link coincided with record high levels of wind generation in Great Britain with generation from transmission connected wind topping 6.3TWh. However, with 2.2GW of the HVDC capacity unavailable, significant volumes of wind output had to be constrained to protect system integration.

This is highlighted in the chart, which shows that the volume of wind bids accepted in the BM classified as system actions hit a record high of 429.8GWh in January. Bids are instructions from National Grid to reduce output and system actions are those taken for wider system needs, such as constraints, on the physical network, rather than simply balancing energy supply and demand.

As a result, the cost incurred through the BM of turning down wind output also hit a record high of £30.9mn.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.

Wind farms only receive subsidy payments when generating and therefore price lost subsidy into their bids.

The impact of the link’s availability can also be seen when looking at the difference in the volume of wind generation constrained in December 2019 and January 2020. Like January, December saw (at the time) record high wind output of 5.6TWh. However, with the Western Link available in December, the volume of wind bids classified as system actions on the BM was significantly lower at 247.1GWh.

As more onshore wind develops, especially in Scotland, in the coming years the problems of constraints will need to continue to be actively managed.

Our Balancing Mechanism Service tracks developments in the BM through our Monthly Webinar, Data Pack and Daily Summary. Please contact l.drummee@cornwall-insight.com for details.

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