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The Role of Distributed Generation in the UK Blackout of 9 August 2019

January 5, 2020

By Paul Homewood


John Constable has taken a closer look at the final reports into last summer’s blackouts.

Hidden away is the critical role played by embedded generation, typically wind and solar farms.

John’s post is pretty technical, but the take home message is that the loss of this embedded generation was much greater than originally thought, and probably played the major role in the blackouts. As the share of such unreliable renewable generation rises, so the instability of the grid will increase.



The final reports into the widespread blackout of the 9th of August last year by the UK electricity regulator, Ofgem, and the British government’s Energy Emergency Executive Committee, E3C show that this is not the case. Distributed Generation is now under the spotlight as a leading cause of the severity of the 9 August blackout, and as a hazard increasing future risks to security of supply.

Both the UK electricity market regulator, Ofgem, and the Energy Emergencies Executive Committee (E3C) of the Department for Business, Energy and Industrial Strategy (BEIS) have now (3 January) released their final reports into the blackout on the 9th of August 2019, a blackout that disconnected over 1 million consumers for nearly an hour with knock-on impacts that persisted for days in many cases and in case, an oil refinery, for several weeks:

Ofgem, Investigation into 9 August 2019 power outage

E3C,  Great Britain power system disruption review

The two studies have different roles. Ofgem’s work, which is now almost complete (there is just one more as yet unpublished technical paper, see p. 10) concentrates on regulatory compliance, that is to say on whether the relevant parties, National Grid, the Distribution Network Operators, and the generators, breached the terms and conditions of their various licenses. In essence it is a retrospective, forensic and essentially historical study.

The E3C work is more forward looking and aims to examine measures that should or are being taken to a) reduce the likelihood of a recurrence of a similar blackout, and b)  improve the way in such a blackout is handled in the event that it cannot be prevented.

The two studies are as far as I can tell entirely consistent, but they are complementary; and they need to be studied together.

Those who have been following the blackout story from the outset, as well as more casual readers of press stories on the blackout, some of which I have discussed in a previous post (“Telling the Story of a Blackout”), will want to know what new facts and analytic interpretation of the blackout emerge from these two studies.

The answer is that there is a good deal here, but it is not initially obvious, and at first glance such readers may be disappointed. While there are some new or at least newish facts these are mainly confined to details, and often about the consequences of the blackout rather than its causes. For example we learn that some four hospitals, not just the much-reported case of Ipswich Hospital, were disconnected during the blackout (see Ofgem, p. 20; E3C p. 19), and that National Grid perhaps over-zealously reconnected the Hornsea 1 before it was confident that the wind farm’s “technical issues”, which had without doubt contributed to the blackout, had been fully understood. We also learn that 371 rail services were cancelled, and 220 part cancelled, with three Transport for London tube stations, and eight rural signalling stations all disconnected, though without significant effect on services (Ofgem, p. 20).

Many of these details are certainly important in themselves, and Ofgem even singles out for particular criticism National Grid’s hasty reconnection of Hornsea (Ofgem, p. 28), but the principal novelty and value of these two documents is not in such material minutiae pure and simple, but rather in the general and cumulatively damning description of weaknesses in the UK electricity system that emerges from this material when it is put into the context of the event overall. It is proverbial that electricity systems shift from stability to chaos in fractions of a second, while the causes of a blackout take weeks and months to understand, but the mists are beginning to clear and we are beginning to get to grips with what happened on the 9th of August.

However, with regard to the story of the blackout, the main narrative has not changed much since last year; a lightning strike trigged the disconnection of, firstly, 150 MW of Distributed Generation, closely followed by the almost instantaneous loss of 737 MW of the Hornsea 1 offshore wind farm. Shortly after that the steam unit at Little Barford Combined Cycle Gas Turbine tripped off. All of this occurred within 1 second of the lightning strike. The consequent drop in frequency triggered further disconnections of Distributed Generators. Additionally, the first of the two gas turbines at Little Barford also now had to disconnect, closely followed by the second of the two gas turbines, and yet more Distributed Generation. (See Ofgem pp. 16–19).

Even in this sketch of the summary it will be obvious to those familiar with earlier accounts that while the main facts remain, the light cast on them has changed significantly, and this results in a somewhat different picture. Attention has switched from the two main Transmission System connected generators, Hornsea 1 and the Little Barford, which have both been fined £4.5 million each for failing to ride through the fault, and is now focussed on Distributed Generation, that is to say on generators connected to, and sometimes said to be “embedded within”, the Distribution Network. These generators are usually invisible to the system operator and can range from very small domestic systems, right up to what are by any standard large onshore wind and solar installations.

The role of Distributed Generation in the blackout was, of course, known from quite early on in the post-event analysis, but the scale is only now becoming fully apparent, though even at this late stage it remains and will remain uncertain. The E3C report goes so far as to remark that “There is a significant possibility that the total volume of loss of embedded generation on 9 August is in excess of the transmission connected generation lost during the event.” Since the transmission-connected generation lost comprises Hornsea and Little Barford, and this totals 1,384 MW, we can infer that somewhere in the region of 1.5 GW of Distributed Generation disconnected in several closely proximate phases over the entire event. That is itself a significant quantity, and suggests that, as the E3C remarks (p. 9), the total generation loss during the blackout was a monumental 3 GW.

But it is not simply the quantity of Distributed Generation that disconnected which is striking. The manner in which it was lost is also important. Ofgem notes, paragraph 2.4.12 (p. 19) that when system frequency fell below 48.8Hz, the Distribution Network Operators (DNOs), disconnected approximately 5% of load, totalling 892 MW of net demand. However, following a hint in the original National Grid Technical Report, Ofgem comments:

The ESO reported that the net demand reduction seen by the transmission system was only 350 MW. This indicates that approximately 550 MW of additional distributed generation was lost at this point. The reasons for this need to be better understood and addressed to avoid it happening again.

The DNOs disconnected 892 MW of demand, but the observed benefit to the system at this time of extreme stress was only 350 MW.

The E3C study gives a little further clarity on this point, noting that “550 MW of embedded generation was disconnected, either as part of the LFDD scheme or via another unidentified mechanism” (E3C, p. 9). The Low Frequency Demand Disconnection (LFDD) scheme is the remedial measure taken during a blackout by the Distribution Network Operators to bring supply and demand back into balance. Thus, much and perhaps all of that 550 MW of embedded generation was disconnected by measures taken to address the blackout. Because of the presence of embedded generators the remedial action take to address a system disturbance actually made the problem worse, cutting the net benefit of the measure.

Ofgem is quite right to say that this problem should be better understood, but it is difficult to see how it can be prevented in the future, as they hope, except by preventing whenever possible the disconnection under LFDD of any area where there is any significant concentration of embedded generation. Of course, that assumes that the system operators are still able to choose which areas will be disconnected, but in a severe system disturbance they may not have that degree of control.

How has this problem with Distributed Generation crept up and surprised us in this way? Who is to blame? Few if any elements within the UK electricity supply industry come out well from the 9th August blackout. Both Hornsea and Little Barford have been penalised. But neither of them are embedded generators, and they have no role in the management of such generation. National Grid was not fined, and superficially emerges from these studies exonerated: Ofgem puts the point unambiguously:

We have not identified any failures by the ESO to meet its requirements which contributed to the outages.”

But this is obviously as much a comment on the licence terms as the performance of National Grid, and both Ofgem and E3C are sharply critical of several aspects of its conduct both before and after the blackout, including embedded generation, Ofgem even remarking that:

[…] the ESO could have been more proactive in understanding and addressing issues with distributed generation and its impact on system security. (p. 22)

The implication seems to be that while National Grid was not, legally, in breach of its licence as Electricity Systems Operator, Ofgem has concluded that it has been complacent in its attitude towards emerging and novel problems in the UK electricity system. Many commentators, including Colin Gibson and Capell Aris, former National Grid employees, have said as much over and over again (Former National Grid director says ministers should impose limits new wind and solar farms to help avoid power cuts). It will be interesting to see what comes of the E3C requirement that National Grid review the crucial Security and Quality of Supply Standard (SQSS) with the aim of understanding the “explicit impacts of distributed generation on the required level of security” (p. 15).) If the consumer interest is respected this could be very interesting.

Taken together these studies of the 9th August blackout report systemic fragility problems in the UK electricity supply industry, but not only within the production side of the industry. National Grid, the generators, the DNOs, none emerge smelling of roses, but the E3C also observes that the consumer sector itself is poorly prepared (p.18ff). As a matter of fact, they are encouraging consumers of all kinds to develop “strong business continuity plans” covering “a range of credible power disruption scenarios”. This is MBA Jargon, but is not too hard to put into everyday French: Sauve qui peut.

It seems probable that consumer side weakness is the outcome of a long period of robust electricity supply, under the CEGB and its inheritors, meaning that consumers never had to test, adapt or even go to the difficulty and expense of developing measures that ensure their lives and businesses are robust in the context of a fragile electricity system. They could rely on the system. That is not the case today.

The costs of a largely decentralised generation portfolio, much of it composed of low inertia generators such as wind and solar, are not limited to the technical athletics of the System Operator, but also involve the need for a forewarned and forearmed consumption market. Thanks to energy and climate policies, British consumers from households to hospitals must now ensure that they are able to handle not only the more extreme grid management measures required by a “smart”, “clean” system but also the consequences emerging when those measures prove inadequate. Taking up the slack, which is what “strong business continuity plans” ultimately means, will not be cost free.

  1. January 5, 2020 10:32 pm

    Bottom line – come the power cut, you’re on your own.

  2. Joe Public permalink
    January 5, 2020 11:02 pm

    Bloody hell, that was challenging for this reader to get his head around the nuances & implications.

    On a brighter note, whilst searching for something else, I stumbled across this gem reported 3 years ago by NaLoPKT’s favourite BBC Energy and Environment Analyst:

    “UK ‘need not fear electricity blackouts’ says ex-National Grid boss”

    • Robert Christopher permalink
      January 5, 2020 11:49 pm

      I do remember an employee survey at my company where our site was, unlike the other site, not frightened about the risk of redundancy, at all! 🙂
      There was little difference in the risks, but we were resigned to it (for the N’th time) as an IT hazard of the 1990s.
      I see similarities here. While hospitals have their own (diesel generators), what are dentists in the middle of treatment to to, whether it is a simple filling or a root canal filling?
      What will happen to the uncooked chickens in domestic ovens – and there will be hell to pay when the workers get home and expect their tea!
      We can improvise, but we will have lost a 1st World National Grid, all for political spin.

      • Gerry, England permalink
        January 6, 2020 2:04 pm

        Thank the Lord for gas….oh, wait, they want to take that away from us as well.

      • Dave Ward permalink
        January 6, 2020 4:07 pm

        “What are dentists in the middle of treatment to do, whether it is a simple filling or a root canal filling?”

        Funny – I was thinking of exactly that, the last time I was lying back in his chair!

        “Thank the Lord for gas….oh, wait, they want to take that away from us as well”

        There seems to be a disconnect (sic) between various agencies:

        “Major project to replace ageing gas mains in North Walsham”

        “Project authorising engineer Dave Nolan said: “The new pipes will be in service until around 2100 helping ensure people continue to enjoy safe and reliable gas supplies for cooking and heating”

  3. January 6, 2020 2:50 am

    Reblogged this on ajmarciniak.

  4. January 6, 2020 6:38 am

    Despite all the warnings by experts such as Colin Gibson and Capell Aris, the government and its regulator Ofgem have stupidly listened to NGOs (such as the Sustainability Development Commission), those with vested interests (such as the renewables industry) and the media (such as the BBC) and pushed ahead with promoting distributed generation and a “smart” grid (beware anything with the label “smart”). Even today the greens are pushing for more and more distributed generation. With luck this event will be a wake up call to the government, but I fear we will need many more blackouts, and possibly civil unrest, before sense returns to government policy.

    In the meantime, as Oldbrew says, you are on your own. Increase your stock of candles and if possible get a home generator and supply of fuel.

    The disastrous outcome of renewable energy (increased fuel prices and reduced reliability, not to mention the impact on the countryside and on peoples’ health) is a fine example of the law of unintended consequences, which seems to be a feature of all schemes promoted by greens and environmentalists.

    • Athelstan. permalink
      January 6, 2020 10:38 am

      I’d like to add to that, but find that once more you’ve admirably covered it Mr. Bratby.

      Well said indeed but alas, if heard at all: your wise words will fall on deaf ears.

  5. Nancy & John Hultquist permalink
    January 6, 2020 7:00 am

    Candles have a nasty habit of burning things.
    Go with LEDs — say a dozen or so garden path lights.
    Placed in a sunny location, but turned off. Also, go for a couple of LED camping lanterns.
    Search with ‘images” for Led lawn lights.

    • January 6, 2020 8:48 am

      It’s not just candles though. As I discovered when I lived in the Philippines in the early 1990s, where they were having problems with the Sucat II power plant, lighting is the easy bit – we had rechargeable lanterns which were adequate.

      It’s also the problem with the fridge ceasing to be reliable. I had to buy food on a daily basis, and then the shops also not keeping their food properly (the stink of off meat as you entered the supermarket was nauseous) so I ended up buying tinned food for safety.

      It’s also the problem with no a/c (for UK, read heating) I became lethargic as I was constantly too hot and my son got prickly heat too frequently.

      Then we had water problems, with no water from about midday onwards.

      Life was tough, it was an effort just to survive – and we lived in an upmarket area just round the corner from the President!

      I remember the power cuts caused by the dockers strike, and the winter of discontent. At least we had gas fires in several rooms so we did not freeze. Not so lucky now, as we might have gas c/heating but it’s useless without power.

  6. January 6, 2020 7:51 am

    Reblogged this on Climate-

  7. Bob MacLean permalink
    January 6, 2020 9:23 am

    Wind farm giant Ørsted cuts job after discovering wind is less effective than previously thought

  8. January 6, 2020 10:14 am

    Reblogged this on Wolsten and commented:
    I cannot see how this issue can be ignored for much longer as it is clear that the technical limitations of renewables are finally coming home to roost.

  9. john cooknell permalink
    January 6, 2020 12:19 pm

    The problem is embedded generators have tended to use vector shift for loss of mains protection, and the actual type of relay and manufacturer they nearly all chose, doesn’t work properly or reliably.

    In other words the consensus has led to failure, sounds familiar.

  10. jack broughton permalink
    January 6, 2020 12:28 pm

    It seems that all the distributed generators will need to be fitted with frequency controls if they are not to fail as soon as the frequency dips in our “Smart grid”: this will prove very costly and will no doubt be another subsidy for the greens. Asynchronous generators will not correct frequency droop, although they help with voltage dips.

    • January 6, 2020 3:58 pm

      It will also depend on how much demand reduction they can get, which we will pay for through our bills.

  11. January 6, 2020 1:37 pm

    You don’t need complicated analyses to understand that unreliable power sources like wind and solar power decrease the reliability of the power grid. What you need are dynamic leaders like Donald Trump who understand how to build things and get things done. Leaders like Trump inherently understand that inefficient and unreliable power sources aren’t helpful to the economy, so they don’t waste time trying to understand their details.

  12. Hugh Mann permalink
    January 6, 2020 3:35 pm

    “550 MW of embedded generation was disconnected, either as part of the LFDD scheme or via another unidentified mechanism”

    What? Surely they know what power went missing and from where, and can do the sums?

    “The Low Frequency Demand Disconnection (LFDD) scheme is the remedial measure taken during a blackout by the Distribution Network Operators to bring supply and demand back into balance. Thus, much and perhaps all of that 550 MW of embedded generation was disconnected by measures taken to address the blackout.”

    Do the Distribution Network Operators not know how much they disconnected?

    • January 6, 2020 5:27 pm

      They know the connected capacity, but they do not know how much power is being produced at any given time – it depends on the wind and the sun.

      • Dave Ward permalink
        January 6, 2020 5:57 pm

        “But they do not know how much power is being produced at any given time”

        A ludicrous situation – and one which would need to be corrected before there is a cat in hell’s chance of a “Smart” grid ever functioning the way we are told it will. Essentially EVERY solar & wind installation (however small,) that is grid connected, will need to have an internet (or mobile phone) link) and be reporting in real time to a central site. Actually setting up such a network is, of course, another matter entirely – you’ve only to see the utter shambles TPTB have made over the Smart Meter roll out! Then consider how those signals will get through IF there are still power cuts…

      • StephenP permalink
        January 6, 2020 6:03 pm

        I still have a nasty suspicion that they were trying to increase the proportion of wind generation, as they were in the high 40s and shut down the 550MW of ?conventional generation to get the wind figure up to over 50% so they could crow about it.
        This would be strenuously denied of course.

  13. It doesn't add up... permalink
    January 6, 2020 8:59 pm

    There’s actually a whole bunch more to digest and infer from the two reports. OFGEM’s #1 action item is a review of spinning reserve and inertia levels – which they blame on National Grid not having raised the issue, despite being the regulator who set the standard, and despite the previous 2008 event also suffering from loss of “embedded generation” on a significant scale. It has been a big wake-up call: the measures recommended then have not been fully implemented over 10 years later. The performance of such backup as was contracted was somewhat less than it should have been

    The overall performance of frequency response providers was generally inadequate. This includes mandatory frequency response providers that are required to provide automatic frequency response by the Grid Code and commercial frequency response providers. Primary response providers (required to deliver a response within 10s) under-delivered by 17% and secondary response providers (required to deliver a response within 30s) under-delivered by 14%. Mandatory response providers, and commercial Fast Frequency Response providers of dynamic primary response (required to provide a continuous, proportional response to the change in frequency) performed particularly poorly, under-delivering by approximately 25% respectively.

    That last is code for grid batteries. So we need 33% more to cover the 25% underperformance, and equally the cost is 33% higher than budgeted.

    Then there is the extremely cavalier attitude of Ørsted in powering up their windfarm to capacity when they knew that they hadn’t controlled for the very voltage oscillation amplification that tripped them out, and they restarted before they had fixed that problem with software or had permission to do so: £158.75/MWh is a big incentive to override safety concerns. Again, regulation on testing has proved totally inadequate – OFGEM asleep at the wheel. It’s like allowing an aircraft manufacturer to put an aircraft into service knowing that in certain conditions, the wings could vibrate and fall off. Moreover, investigating the issues internally, Ørsted identified that this stability issue with its voltage control system had occurred around ten minutes prior to the incident on 9 August but had not caused de-loading at that time. So if they had been duly cautious, they would have ramped down output and warned the grid of the need to do so. It is perhaps not a surprise that the CEO of the UK operation was sacked last month, probably after the reports were first produced, which happened to be just before the election.

    There’s a lot more, but this is a blog comment, not a detailed critique.

  14. Vernon E permalink
    January 7, 2020 11:19 am

    I assume that there must be others under the same delusion as Dellers in his latest post. Fracking was not stopped because of environmentalists. It was stopped because our shale is impermeable to gas flow – as was easily predictable -and Cuadrilla and their Australian owners are on the point of bankruptcy as a result.

    • It doesn't add up... permalink
      January 7, 2020 12:23 pm

      I think that the verdict on the produceability of Bowland Shale is “not proven”. It is quite clear that government called a halt following the ML 3 tremor, and that Cuadrilla had yet to test with alternative fracking fluids.

    • dave permalink
      January 7, 2020 1:00 pm

      “…our shale is impermeable to gas flow…”

      Not so, according to Cuadrilla:

      Of course, for the present, I have no way of knowing if they are truthful.

  15. Vernon E permalink
    January 7, 2020 4:17 pm

    Dave: I have not seen that report before but I am familiar with the previous test results. I don’t think they are being truthful. They demobilised at Preston and their owner’s shares have dropped dramatically. They make reference in the above to 250 MCFD but the “beak even” in Marcellus (US) shale is about 600 MCFD. In their earlier projections Cuadrilla claimed they expected over 2 MMCFD. Not credible. I wonder what they are up to?

    • January 7, 2020 6:40 pm

      What about all of the other places they were going to test?

  16. January 7, 2020 6:39 pm

    In 2017, the outgoing CEO of National Grid, Steve Holliday, seemed rather upbeat about the possibility of blackouts:

  17. Vernon E permalink
    January 8, 2020 4:15 pm

    Paul: With the huge costs of drilling inflated by a hostile public and hostile government along with what is now obviously a poor chance of a viable result I don’t think there will ever be another attempt to produce gas or oil from UK shale (unless there is a dramatic change in international circumstances like all-out war).

  18. January 9, 2020 11:17 pm

    Power grids are usually designed with some overcapacity which is here in order to smoothe out all possible and probable eventualities that go wrong. Things go wrong all the time. Small things every day, every hour, big things every so often. When you design your overcapacity one must establish what kind of risk they want to cover with that. More capacity means more cost, lower likelihood means less incentive to provide for it. This means that no electrical system is entirely foolproof. That would be excessive. But when the overcapacity that is here to protect us from unlucky events is used to iron out flicker electricity, it’s not available anymore to do what it is supposed to do. iron out the wrinkles. And when such a wrinkle hits us, we are naked. Renewable energy has made our electrical systems brittle again. Because renewables refused to pay for the capacity they needed in order to function. What’s a subsidy again?

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