Page 28 - October 2019

WHEN THE

LIGHTS GO OUT

On a Friday afternoon in August, large parts of the UK linepack and gas storage. In the gas
experienced the biggest power outage in a decade, leaving network, imbalances between supply
thousands of people stranded on trains for up to nine hours and demand can be met for a period by
and cutting electricity to almost one million users in England varying the pressure of the network and
by using gas storage.
and Wales. Paul Verrill, Director of EnAppSys, looks at why it One of the charges levelled at
happened and why these kinds of events could become more National Grid has been whether it
common as we push to decarbonise the energy system procured enough electrical reserve and
frequency response capacity. Their
response has been that they held the
I n the late afternoon of 9 August chaos was as a result of a combination under their licence conditions.
capacity required by the regulator
Ultimately, a detailed investigation
of smaller events all lining up like the
2019, the British electricity system
suffered its first major power cut
holes in Swiss cheese. Individually,
is ongoing and corrective actions will
since May 2008.
come out of it on all sides. From what
these small events would not cause a
The loss of two power stations
and associated loss of embedded problem, but together they compound we know to date, the summary seems
to create a large event.
to be a reminder that there is a balance
generation brought about a low system The event is not unprecedented between cost to the consumer and
frequency due to more electricity as a similar one occurred 11 years stability of supply and a line is drawn
demand from the system than the ago, but the initial power cut was somewhere that means 100 per cent
generators were supplying. amplified by the chaos it caused and security of supply is never guaranteed.
Reserve power and specialist led to many questions about whether Given this fact, the summary
frequency response services were decarbonisation was a contributory suggests that system operators need
not sufficient to meet the immediate factor. Renewable supporters and to consider closely the impact of
shortfall in demand and the next line detractors each took opposing system disconnection and prioritise
of defence, automatic interruption of positions on the causes. accordingly. Depending on criticality,
customers, kicked in. end consumers, particularly hospitals
More than a million customers lost The last similar frequency and national infrastructure, need to be
supply for around 30 minutes, but the prepared for a loss of utilities and more
main disruption occurred due to the event happened in GB in 2008, specifically how to recover from them.
impact on transport systems during the but the impact was lower The last similar frequency event
Friday peak travel periods, with many with around half a million happened in GB in 2008, but the impact
workers commuting home out of London. customers affected was lower with around half a million
While the event was transient, customers affected. While the 2019
the disconnection of the substations event was relatively transient, the 2008
feeding the GB rail network and, in Running electricity networks with event started as a frequency event, but
particular, those lines out of London high renewables as part of the fuel also involved a shortage of generation
required individual trains and electrical mix is different to running networks for a longer duration as, following
systems to be manually reset, causing with conventional power plants. Due the initial event involving two power
disruption late into Friday evening. to the technologies employed by wind stations, further power stations came
Power to airports and critical and solar assets, the system runs offline causing a squeeze on supply.
infrastructure, such as hospitals, was with less inertia (that resists these While the type of disruption that was
also lost and some backup systems short period imbalances) and this has caused was similar to the latest event,
designed for such an event either failed led to the deployment of fast-acting the number of people impacted seemed
or were inadequate. generators and storage being used to to be lower, with less widespread
As in all complex events, the overall provide this stability. transport disruption.
level of the event and the subsequent A parallel in the gas network is In terms of gas supply, the last

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