Day Of Havoc For Britain’s Grid

By Paul Homewood

While I was away last week, Kathryn Porter had a comprehensive article in the Sunday Times about a day of havoc for Britain’s grid on 29th May:

 

 

https://www.thetimes.com/article/93acbb75-9b20-443a-8125-387de3b4d16f?shareToken=098d4ee1d1539d5b2d9e151d1b445e01

The immediate cause appears to have been NESO’s overestimation of wind power on what was a pretty windy day:

 

As a result, NESO had to perform heroics in attempting to balance the grid. Kathryn notes:

The grid required 24,742 balancing actions across that day, May 29 — thousands more than usual. In essence, these actions are orders from the control room to ramp power stations up or down to keep supply and demand finely balanced.

The cause she says was primarily high wind-power output and poor forecasting from the system operator. She writes:

The level of discrepancy between what was forecast and what was generated was extremely difficult for the control room to manage that day, and would typically trigger substantial re-dispatching (sending new orders to power stations to change their running plans).

This re-dispatching worked both ways, up and down. For instance, we were importing from France over the IFA2 undersea cable, while exporting over its sister link, IFA1 at the same time.  Similarly some CCGTs were told to reduce power, while others in other regions were asked to ramp up output.

There is always an element of balancing on the grid, but evidently it was tested almost to destruction that day.

Kathryn rightly focusses on the software implications faced by NESO. But I want to concentrate on the role of gas power that day, which was crucial in balancing the grid, not just on a national basis, but regionally too, a problem which is too often ignored.

The BMRS chart below shows how generation from CCGT fluctuated substantially from minute to minute, both to meet shortfalls but also to compensate for surges in wind output/drops in demand.

A very basic question is posed – what happens when all these CCGTs have been shut down?

https://bmrs.elexon.co.uk/generation-by-fuel-type

While we are on the topic, the next chart looks at interconnector flows, which also had to be ramped up and down, notably in the early evening when wind power dropped away:

As Kathryn points out, Neso made multiple interconnector trades up to 2pm, all of which were exports, and all at negative prices, meaning Britain was paying other countries to take away its excess power. (The BMRS chart does not show outflows).

Put simply, we are not only highly dependent on gas power and interconnectors to provide electricity when renewables fall short, we also need them to export surplus power and balance the grid minute to minute.