SRC-238

National Electricity Transmission System Security and Quality of Supply Standard, Version 2.12, 29 May 2026

Published claims resting on this source

• CLM-0780 The UK rules for connecting power stations set a hard limit on how much generation one fault may disconnect at once: 1800 MW for a fault on the station's own connection, and nothing at all for a fault on a single transmission line.
• CLM-0782 UK rules limit the overhead line between a generating unit and the grid to 5 km for units producing at least 2000 gigawatt-hours a year and 20 km otherwise. A 2 gigawatt plant counted as one unit would cross that threshold even if it ran only about 11 per cent of the time, but the rules define a generating unit as any apparatus which produces electricity, and counted that way a receiving site made of many converters would fall under the 20 km limit. Which reading applies is not settled.
• CLM-0786 In December 2025 the UK system operator changed its own connection standard to allow a single large direct-current converter to carry more power, because the old 1320 megawatt cap was forcing offshore wind farms to build extra cables, and it priced the extra frequency support at about 12 million pounds a year.
• CLM-1211 Britain's main transmission grid runs at 400 kV and 275 kV, and parts of the 132 kV network in Scotland. On the 400 kV network the voltage normally stays within 5 per cent of its nominal value and never beyond 10 per cent outside abnormal conditions. The rules read do not say how the connection voltage for a given plant is chosen.
• CLM-1487 In Britain, the amount of fast back-up power kept ready depends mainly on the biggest single block of power that could be lost at once; the rules do not set it by fuel. So a space solar station would need about the same fast back-up as a gas power station whose biggest single loss is the same size. A 2 GW space plant would be a bigger single loss than the 1,800 MW Britain now plans for, if one fault could take all of it. A satellite in geostationary orbit also passes through the Earth's shadow each night for about six weeks around each spring and autumn equinox, for up to about 70 minutes. Those times can be predicted exactly, and other power stations would have to cover them.

Cite this