British power cut triggers probes [NGW Magazine]
Over a million British consumers lost electricity supply and thousands of commuters were left on stranded trains following an unexpected power cut during the rush-hour on August 9. Traffic lights, an airport and a hospital were also hit.
The scale of the disruption, which lasted for hours after the technical restoration of power to the grid, shows the need for greater security of supply than before, according to energy economist Dieter Helm, as the UK strives towards a “net zero carbon” emission future. He suggests it might be cheap at almost any price.
A lightning strike – a common enough event – hit part of the network, affecting some 500 MW of distributed capacity; and immediately after and within seconds of each other the Hornsea off-shore windfarm and the Little Barford gas power station both stopped generating.
In all, about 5% of Britain’s electricity demand was turned off to protect the other 95%. This has not happened in over a decade and is an extremely rare event, National Grid said. National Grid submitted its confidential initial report a week later, which Ofgem decided to publish; and it will submit a more technically detailed report September 6.
Other commentators also said that it showed the problems that could arise with the arrival of too much intermittent generation capacity too quickly, and that a vacuum that had opened up between the responsibilities of the distribution networks and the high-voltage network operators.
The total generation lost from the two events was 1,378MW, and the frequency fell to 48.8 Hz, which is below the statutory range of 50.5Hz – 49.5Hz. National Grid Electricity Supply Operator (ESO) however said it had the statutory minimum 1,000 MW of automatic “backup” power, according to the Security and Quality of Supply Standards (SQSS), which is intended to cover the loss of the single biggest generator to the grid.
All the backup power and tools the ESO normally uses and had available to manage the frequency were used (this included 472 MW of battery storage). But this was not enough and the Low Frequency Demand Disconnection scheme “automatically kicked in to recover the frequency and ensure the safety and integrity of the network,” National Grid said.
But among the questions to be answered is whether National Grid had done enough to secure rapid-response back-up to solve the frequency problem, even if it was acting strictly in accordance with the SSQS, which after all it had been involved in devising. Frequency variations have become commoner as more intermittent power has come on to the grid.
Ofgem will try to find out if any of the parties involved – National Grid ESO, National Grid Electricity Transmission, the 12 distribution network operators in England and Wales, as well as generators RWE Generation (Little Barford Power station) and Orsted (Hornsea) – breached their respective licence conditions. Fines or other enforcement actions are possible if Ofgem concludes that any of them did.
Ofgem will want to know if the companies made the right decisions both in the numbers of customers disconnected and their suitability.
The rail regulator is also involved, as its own sector’s supply security systems might need an overhaul: commuters suffered the most from the outage.
Government review overdue: Helm
More important than the Ofgem probe, according to energy economist and author of the government-commissioned Cost of Energy Review, Dieter Helm, will be the government’s investigation, under the Secretary of State for Business, Energy and Industrial Strategy (Beis), Andrea Leadsom.
Beis should consider the costs of extra firm and flexible capacity and compare these costs to those the economy experienced from this short, sharp shock, he said, soon after the power cut.
“The costs of too much capacity are trivial compared with too little – and will become more so as the economy digitalises…. All our main infrastructures now depend upon a reliable supply of electricity, as they all depend on communications networks.
“We need a higher level of security of supply than ever before, and as we complete the transition to a digital economy (and net zero) we will need ever more security. What was good enough a couple of years ago is not now. What we need in the next decade is a lot more security…. More renewables mandated, by the net zero legal requirement, mean more equivalent firm power,” he continued.
He said the third point was that Ofgem is determining how much investment, and therefore resilience, the networks will be allowed to build in after the periodic reviews. More resilience means more investment and capital maintenance cost, something Ofgem will have to consider (along with how far the network companies have been doing sufficiently in the past).
Helm has an interest in this, as Beis and the finance ministry have sat on his Cost of Energy Review for almost two years, while working towards a White Paper.
The optimistic take on recent events is that the power cuts will be a wakeup call to Beis and the government to get on with the White Paper and the legislation that will be required to implement the evolutionary changes now urgently required, he said. Government, he said, is the effective customer for all new generation.
The letter of the law, not the spirit
Speaking to NGW late August, Jeremy Nicholson of consultancy Alfa Energy and formerly the spokesman for the Energy Intensive Users Group said that he had not seen any evidence that National Grid had breached its licence condition.
But while everything might have gone according to the book, the question is whether the situation should have reached the stage that it did, with the 1.1mn disconnections, he said.
“Since the last major power cut of 2008, a lot more wind and solar is now on the system. Those technologies do not provide the inertia needed to stabilise the system which buys time for more capacity to come on line.
“For inertia you need coal, gas or nuclear. If a generator goes off, or there is a surge in in demand, this can cause a shift in frequency and there are measures to provide a frequency response in a very short period of time. This can be pumped storage, or industrial load-shedding or battery storage. But having battery storage on stand-by is expensive.
“Did NG contract enough frequency response in advance, in the event of a major trip? NG's report showed that it also lost 500 MW capacity when some distributed generation, much of it solar, was hit. Should National Grid have had more back-up available, then?
“National Grid and Ofgem together worked on the security of supply standard, so that is one question for Beis to examine. National Grid might be legally protected if it said it followed the rulebook to the letter; but to what extent can it claim to have the appropriate standards, or that it took the right measures to achieve stability?
“A relatively small initial loss of capacity caused a major disruption in most regions of England. While there is no need for a gold-plated system, a 1,400-MW supply loss is not an unforeseeable event. If it can be expected to lead to a further 4-500MW of distributed generation, beyond NG's control, going offline, that needs to be looked at.
“According to one source, the variance of frequency performance has risen, and frequency events come close to the 49.5 Hz lower limit more often now. I have heard that NG has recently changed its rules for procuring enhanced frequency response. Correlation does not necessarily imply causation, but the enquiries do need to look at this.
“At the end of the day, what is an adequate level is somewhat arbitrary. But if the system encounters more intense, prolonged or common low-frequency events, that have followed changes in NG's back-up procurement rules, then that raises some questions.
Another problem Nicholson pointed out was on the communication front. “National Grid did not make any announcement for 90 minutes, until power had been fully restored, which is puzzling. Clearly their priority was dealing with the emergency, but there may be lessons to be learned here in terms of communication,” he said.
“I appreciate it is part of National Grid’s job to deal with PR in relation to the Net Zero goals, etc, but they do have a day-job as well. How did we get there in the first place? No system is infinitely resilient. This was not a supply-demand problem. There was low demand and plenty of supply. Demand has been shrinking anyway, making it easier to phase out coal; and plenty of supply has been contracted, but not enough of it apparently is instantaneously available. So it could be more a matter of contractual, not infrastructure, inadequacies. Does National Grid have the right procurement practice in place or is it cutting corners?”