Time to think about resilience

What happens when the lights go out?

In the late afternoon of Friday 9 August 2019 a lightning strike hit a transmission circuit at 4.5km from the Wymondley substation. It was a pretty normal day in the UK transmission system but that single bolt of lightning caused significant disruption. Trains were stopped for hours and the country took a significant time to recover.

According to the technical report into the events of the day, “Prior to 4:52pm Great Britain’s electricity system was operating as normal. There was some heavy rain and lightning, it was windy and warm – it was not unusual weather for this time of year. Overall, demand for the day was forecast to be similar to what was experienced on the previous Friday. Around 30% of the generation was from wind, 30% from gas and 20% from nuclear and 10% from inter-connectors.”

The lighting strike turned off the power to nearly one million people. Although power was restored within an hour the impact went on late into the evening and was particularly felt in the rail system with one fleet of trains unable to reset itself when the power returned. This caused significant disruption (and discomfort) for those stuck on the trains awaiting rescue.

Was it the fault of wind and solar?

Much has been made in the press of the changing nature of the electricity grid and the impact of more generation embedded in the system. Logically, more decentralisation should build in resilience as large single points of failure disappear. However it is clear from the August power cuts that these key single points still exist. In such a complex interdependent system small disruptions can still have a much broader impact. Although in this case the lightning strike actually caused a very short term impact – it was the lack of resilience of certain critical elements to voltage drops which had the largest effect. Had the drivers been able to restart the trains for example, the impact would have been significantly reduced.

In thinking about energy resilience it is important to not use just past events to plan for the future. In many ways the root cause is of less importance than its impact. A quick read of the list of global power outages shows the broad range of root causes which can impact the system, many of which are beyond our control, including:

  • weather events – many large blackouts around the world are caused by large storms and in particular ice build up on power lines and lightning

  •  solar storms – space weather impacting IT systems and electricity grids is inevitable, according to scientists

  • technical failure – sometimes equipment does fail, as with the London blackouts of 2003

  • third party intervention – this could be as simple as a digger hitting a cable or a cyber attack

So what can we do?

While you cannot plan and prepare for every eventuality, what you can do is test systems for recovery and assess potential impacts. Following the August power cuts it is important for organisations (and individuals) to consider the following points.

  • What is the impact of even a short interruption to key supplies like power, water and gas to our activities, and in particular to our customers?

  • Is there any way to physically test how we would recover in the event of a loss of critical supply, even one of short duration?

  • Can we look for ways to build natural resilience into our systems? For example using renewable technology through Local Energy Systems.

As the system evolves and further decentralises, considering our own more local systems becomes increasingly important. A decentralised system can be both more and less resilient in different ways and users need to consider how best to mitigate the impact of system disruptions in such a rapidly changing environment.

Written by John Armstrong

John Armstrong is a Chartered Engineer and Fellow of the Institute of Mechanical Engineers, with a degree in Mechanical Engineering and a global energy MBA. He worked at E.ON for 15 years until June 2020, including roles in engineering governance, asset risk and safety, and most recently as Head of Operations for E.ON’s decentralised city energy systems.