Britain's grid problem, as everyone tells it, runs north to south. Too much Scottish wind, not enough wire to bring it down, and a bill for turning the turbines off.
That story is true. Since the start of June, the Scotland-to-England boundary has been over its day-ahead limit on 66 evenings out of 114 — a median of 118% of its capacity, peaking at 329% on 2 July. Managing it is routine, constant and expensive.
On the evening of 22 September it was running at 58%. Its 101st worst evening out of 114. Quiet.
Which makes it a useful night to look at what else the system was doing, with the loudest thing on the network briefly silent. And there was a great deal going on. The day before, NESO had shut Britain's export cables to Denmark and Norway, filing the reason as Margin Extremes — the clearest statement a system operator can make that it expects to be short. It never was. No margin notice followed, and the evening ran long more often than it ran short. What it was instead is the subject of this piece.
Between 4:25 and 8pm, NESO paid two gas stations in Wales to generate 2,325 MWh more than they had planned, and paid gas plants on the Humber, in Lincolnshire, and a fleet of batteries spread across the country, to generate 2,035 MWh less.