Value chain · CLM-0795
In plain terms
Britain's system operator says that at the lower inertia level it is moving to, losing 2000 megawatts at once would be enough to start disconnecting customers, and losing 3.3 gigawatts at once could cause a nationwide blackout.
The claim as recorded
The GB system operator's Frequency Risk and Control Report 2025 states that at a system inertia of 102 GVA.s an infeed loss of at least 2000 MW would be required to initiate a 48.8 Hz frequency deviation, that 48.8 Hz is where the first stage of low frequency demand disconnection begins with subsequent stages between 48.8 Hz and 47.8 Hz, that the only two low frequency demand disconnection events since GB electricity industry privatisation in 1990 occurred on 27 May 2008 and 9 August 2019, and separately that an infeed loss of 3.3 GW would be needed to trigger a 1 Hz/s rate of change of frequency at 102 GVA.s, a level at which the report expects most embedded generation to trip on loss-of-mains protection and describes the consequence as a nationwide power outage scenario.
Scope and limits
The source is not writing about space-based solar power and makes no SBSP claim. The 2000 MW threshold is stated as a floor at a specific inertia level and would move with the response services actually held; the report's whole purpose is to show that additional dynamic containment procurement mitigates these risks. It may NOT be cited as "a 2 GW SBSP plant would cause customer disconnection". What it supports is that a 2 GW single-point infeed loss sits at the boundary of the event class GB designs against, which is a materially weaker and defensible statement.
What it assumes
That the 2000 MW figure is the source's own modelled threshold for initiating a 48.8 Hz deviation at exactly 102 GVA.s inertia, with no other mitigating service assumed. The report's phrasing "at least 2000 MW" is a floor, not a precise value.
Where it comes from
LFDD threshold, verbatim, section 6.4.2: "The first stage of low frequency demand disconnection (LFDD) starts at 48.8 Hz and then subsequent stages apply in the range 48.8 Hz - 47.8 Hz. Under a 102 GVA.s system condition and to initiate a 48.8 Hz deviation, we would have an infeed loss at least 2000 MW." Historic events, verbatim: "The previous two occurrences of LFDD happened on 27 May 2008 and 9 August 2019 over a decade apart. These are the only two LFDD events since GB electricity industry privatisation in 1990." Nationwide scenario, verbatim, section 6.4.3: "Following the trigger of 1 Hz/s RoCoF at a system inertia of 102 GVA.s, it is expected most of the embedded generation would start to trip based on their LoM protection settings. This would result in a national-wide power outage scenario. However, to initiate a 1 Hz/s RoCoF event..., the system would need an infeed loss of 3.3 GW. This level is far greater than the current largest loss we aim to secure and is much higher than any of the historical simultaneous events that we have observed." Reassurance in the source's own words, verbatim: "Proposing 102 GVA.s inertia requirement and limiting the post-fault RoCoF to 0.5 Hz/s provides a security 'buffer' under current and foreseen system conditions."
Basis: system inertia condition of 102 GVA.s; low frequency demand disconnection first stage at 48.8 Hz; RoCoF relay settings mostly at 1 Hz/s
Related records
- Answers question
- QST-012 not published in this release
Cite this
energyaperture.com/c/clm-0795
CLM-0795, Energy Aperture, as of 2025.
Connected records
Other published records linked to this one. A list, not a judgement.
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