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System failure

Officially, Britain’s worse power outage in a decade is being recorded as an unusual event that nobody could have reasonable anticipated.  Dig a little deeper into the National Grid report on the 9 August 2019 blackout, however, and we discover an electricity system that has been allowed to become increasingly unfit for its intended purposes.

The official “cause” of the blackout was a lightning strike on a transmission line which tripped several power generators; causing a loss of power and a dangerous loss of frequency.  Having exhausted all of its emergency backup capacity, National Grid had no option but to disconnect 1GW of demand (in order to preserve the remaining 28GW) causing more than a million users to lose power – including critical infrastructure such as the rail network and NHS facilities.

The problem with this explanation is less to do with what it says than what it omits.  As Jillian Ambrose at the Guardian points out:

“In the last 12 weeks the grid’s frequency has fallen dangerously low, below 49.6Hz, on three separate occasions. Prior to these near-misses the grid’s frequency had not fallen to this extent for at least the last four years.

“National Grid had managed to avoid a wide-spread blackout until now by triggering a ‘low frequency event’ which sends out a call to contracted energy companies for immediate back up, with only 10 seconds’ notice.”

Although seemingly innocuous, this gets to the nub of the system failure behind the 9 August outage.  Since privatisation in 1986, successive UK governments have acted to create a quasi-market for electricity in which generation, transmission and supply are operated by a series of different private for-profit corporations.  Power producers compete at auctions to supply electricity to the privately-owned grid (which is responsible for ensuring there is sufficient supply to meet demand) while supply companies purchase electricity to sell on to business and household consumers.  All of this quasi-market activity is overseen by Ofgem – the regulator charged with ensuring competition between the various corporations, while keeping prices as low as possible for consumers.

Despite being among the largest and most complex machines on the planet, the electricity grid in 1986 was simple by today’s standards.  A small number of large (>1GW) coal, nuclear and gas power stations (located across the UK) provided the power required by businesses and households.  The discovery of large North Sea gas reserves had provided the incentive for a switch from coal to gas; but this had little impact on the grid because both systems (and nuclear) involve creating heat to make steam to power giant steam turbines. 

Indeed, gas had a couple of advantages over coal.  Most obviously, gas creates less particulate fallout than coal; making it a little cleaner and allowing its proponents to label it a “transition fuel.”  Less obviously, combined cycle gas turbine power stations can respond to fluctuations in supply and demand far faster than the coal plants they replaced.

Crucially, the 1986 grid had massive inertia built in.  Even if a power plant went offline, the giant steel turbines would continue to spin; maintaining frequency for several seconds and giving the grid operator the time to bring spare capacity online.  By the 1990s, however, this backup inertia was being diluted as government policy shifted to add so-called “renewables” to the mix.  Various government subsidies were used to encourage businesses and affluent households to install wind turbines and solar panels as a first step in the so-called decarbonisation of Britain’s electricity industry.  Government policy also instructed the grid to prioritise electricity generated from renewable sources in preference to fossil fuel sources.

In the early 1990s, with wind and solar accounting for less than 10 percent of overall supply, there was no need for overhauling the grid, as intermittency could be managed with the much larger fossil fuel capacity.  But as wind and solar capacity has increased – on 9 August 2019, they accounted for nearly half of the UK’s electricity supply – the system has become increasingly vulnerable to sudden fluctuations in frequency (which, left unchecked, would damage the grid hardware itself, as well as household and business electrical equipment connected to the grid).

Energy storage lies at the heart of the problem.  In effect, the spinning steel turbines in a nuclear or fossil fuel power station are giant batteries; acting like a fly-wheel to store some of the energy put into them.  As a result, even when the power source is lost, they continue to generate electricity.  Wind turbines have a tiny amount of inertia but without the weight of a steam turbine, it is intermittent, and so has to be damped out of the system.  Solar panels – which are the only form of electricity generation that doesn’t involve spinning copper coils around a magnet – have no inertia at all.

Battery storage is in its infancy, and has not been deployed on anything like the scale required to maintain frequency in the event of a sudden loss of power.  Moreover, the cost of batteries – while falling – is still far too high to make them a viable alternative to pumped hydro as a storage medium.  But pumped storage has problems of its own – not least people’s opposition to having their homes and villages flooded to make way for the required reservoirs.  In practice, the regulator and the operator have continued to rely on the inertia from conventional power generation to offset intermittency even as the proportion of intermittent generation has increased dramatically in recent years.  Coal-free days, it turns out, are only a good thing if the grid doesn’t get struck by lightning.  This is what Ambrose refers to when she writes that:

“National Grid will accelerate plans for new blackout safeguards to avoid another energy system shock after more than a million homes were left without electricity last month.

“The grid operator admitted after Britain’s biggest blackout in a decade that the energy system’s standards should be more resilient against the risk of unexpected power plant outages.

“In a report for Ofgem, the industry regulator, it conceded that it would need to bring forward a programme to upgrade its safeguards, due by 2022, which could have helped to prevent the mass blackout on 9 August.

“It has also called for a review into whether it has enough backup power to cope with outages after admitting that it did not have enough in reserve to avert the energy system failure.”

The actually series of events in the Ofgem report confirm my earlier report that the timings originally publicised by National Grid did not match the grid data.  The report also confirms that the sequence of events began with the loss of 950MW of renewable electricity at 16.52 (not the loss of the Little Barford gas power station as initially reported by National Grid). 

According to the report, the event began with a lightning strike – a fairly common event – tripping 150MW of distributed power (i.e., a large number of small wind, diesel and solar generators).  Moments later – and possibly a response to this loss – the Hornsea offshore wind farm output fell from 799MW to just 62MW as its operating software acted to prevent damage to the turbines.  Moments (i.e., less than a second) later, one of Little Barford’s steam turbines tripped, taking another 244MW offline (although the station’s remaining turbines continued to produce power).  In response to these losses of power, a further 350MW of distributed generation tripped, bringing the total loss of power to 1,481MW.  Within the next minute, 900MW of National Grid’s 1GW of backup capacity was brought online, stabilising the frequency at 49.2Hz.  Seconds later, however, the gas turbine at Little Barford failed; bringing the loss of power to 1,691MW.  At this point, National Grid had consumed all of its 1GW backup capacity and had no resource to cope with further power losses or frequency fluctuations.  Then, half a minute later (16:53:50) the frequency fell to 48.8Hz; triggering the Low Frequency Demand Disconnection scheme and automatically disconnecting 1.1 million business and household consumers.  In response, and for yet to be discovered reasons, (16:53:58) a third turbine at Little Barford went offline bringing the total loss of power to 1,878MW – nearly double Ofgem’s stipulated backup capacity.

The risk with these details is that too much attention will be given to figuring out the technical causes of the Hornsea and Little Barford failings rather than more important questions about the UK’s energy system as a whole.  As a Guardian business editorial puts it:

“National Grid admitted in its report on the blackouts that it might need to review the rules for how much back-up power it keeps in reserve, and speed up existing plans to toughen other rules that guard against blackouts.

“In the week ahead, the government’s energy emergency committee looks set to turn the glare of scrutiny on to regional energy networks and rail companies too. Its report this week is likely to ask tough questions about why National Grid’s lapse was allowed to engulf planes, trains and hospitals.

“Here again, tedious protocols and preparedness will take centre stage in place of discussions over lightning bolts and the systems that keep the energy grid’s fragile 50Hz frequency steady.

“These are the nuts and bolts of keeping Britain’s lights on, and they matter. It is the responsibility of the companies that profit from running public infrastructure to keep hospitals running and trains on track, and energy companies have prided themselves on this in the decades since public ownership gave way to privatisation.

“If companies believe they are merely defending their record on the events of 9 August, they are mistaken: they are defending the right to profit from an essential service that they had promised to protect.”

Hidden within the technical appendices of the Ofgem report are suitably obfuscated questions about the purpose of the system itself.  Responding to Ofgem questions about the lack of backup capacity and inadequate inertia in the system, National Grid responds that:

“The standards we have had in place for many years have delivered world class reliability – however for what was a rare event on the 09 August the disruption caused to society was something we would not want repeated and therefore we think a review of the standards for security of supply would be prudent to ensure they are appropriate for society and the economy today and into the future and that they reflect the right balance with the costs to customers…

“It is our view that the required level of system resilience should be mandated as this is what is important to society. At each point in time the ESO can then optimise the system to deliver this resilience in the most cost-effective manner. The appropriate level of resilience should be considered as part of any review of the standards for security of supply.

“Mandating inertia or any of the other system variables rather than the required resilience level could lead to unnecessary costs for consumers.”

It is important here to understand that the report is from the grid operator to its regulator rather than to the public.  What these paragraphs are actually saying is that in order to avoid a repeat performance, the regulator does indeed need to review the various safety margins – including inertia (here included with storage as “resilience”) – but that this is going to be expensive to deliver and the cost will inevitably have to be passed on to consumers.  In effect, this is the grid operator expressing the same problem as laid out by energy economist Dieter Helm in his 2017 review of energy for the UK government:

“It is not particularly difficult to set out what an efficient energy system might look like which meets the twin objectives of the climate change targets and security of supply. There would, however, remain a binding constraint: the willingness and ability to pay for it. There have to be sufficient resources available, and there has in a democracy to be a majority who are both willing to pay and willing to force the population as a whole to pay. This constraint featured prominently in the last three general elections, and it has not gone away.”

Indeed, professor Helm was overly optimistic to assume that we could achieve any two of the objectives he examined.  What the 9 August outage and the three near misses leading up to it make clear is that all three are mutually exclusive.  That is, we may have a low-carbon system; or we may have an uninterrupted 24/7/365 system; or we may have a (relatively) low cost system.  What we cannot have is any two of these; let alone all three. 

Given the severe income inequality in the UK, cost can no longer be ignored.  Low incomes are already translating into falling demand across the economy; which, in turn, has caused demand for electricity to fall (empty shops and restaurants no longer need to turn on the lights and heaters) with the result that electricity supply companies are no longer profitable. Barring a redistribution of wealth on a scale that would have made Stalin blush, there is simply no means by which the UK government will be able to meet its climate and energy security aims.  Which is why, at the end of the day, the politicians will collude with the regulator and the grid operator to pretend that the 9 August outage was merely the result of a freak lightning strike.

As you made it to the end…

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