The increased frequency of abnormal weather events such as intense heatwaves, more violent storms and heavy rainfall presents an increased risk to countries’ electricity distribution networks that threatens customers’ power supplies. That’s according to VisNet from EA Technology, the specialist energy management and grid-edge intelligence firm.
As the UK and all of Europe once again experiences record high temperatures this summer and the risk of severe thunderstorms, distribution network operators (DNOs) should expect significant rises in the number of so-called “pre-faults” – that is, a split-second spike in current caused by a breakdown of insulation on the line – on their distribution networks following a heatwave.
Dr David Clements, Data Analytics Manager at EA Technology, explained the issue in the following terms, “We know from conversations with electricity operators in continental Europe that in the days following extreme heat, networks can experience very significant spikes in pre-fault numbers.”
He went on, “The underlying causes of pre-faults during extremely hot weather is still uncertain and needs further investigation. They could be the result of underground distribution cables expanding when the temperature rises, which then warps the cable or causes its insulation to crack.
“We’ve not yet seen the same scale of increased pre-faults in the UK that operators in mainland Europe have to deal with. For now, numbers are noticeably lower than what has happened following heatwaves on the continent, which are typically much hotter than a British heatwave.
“But based on current climate trends, it's only a matter of time before the UK experiences the similar intense heat waves as the rest of Europe. There is a window of opportunity for operators in the UK to prepare for this eventuality.”
Dr Clements pointed to the role of more accurate, granular monitoring to address the pre-fault risk. “By identifying pre-faults more quickly, operators get in front of the problem and make the necessary repairs before the pre-fault gets worse and leads to a full outage.”
He added, “Operators taking pre-emptive action in anticipation of possible disruption isn’t a new development. In 2016, French operator EDF drafted extra repair crews into Paris during a heatwave in the city, in anticipation of needing to deal with a surge in faults in the distribution network due to the higher-than-normal temperatures.
“EDF correctly predicted that the number of faults would rise above expected levels once the heatwave subsided, temperatures dropped, and the cables cooled down.”
But it’s not only extreme heat that can disrupt energy operators’ underground distribution cables. Pre-fault data collected by VisNet from low-voltage networks across the UK between last October and March of this year shows that four of the five major winter storms that the UK experienced during this time period caused a significant rise in pre-fault events.
The pre-faults that occurred during each storm were caused by rain that permeated into the ground and made its way via cracks in cable casings into the electrical wires inside.
In particular, what stands out from the VisNet data is that the largest spike in pre-fault events took place over a three-day period from 4 to 6 January.
This was not due to a storm but instead because of three days of sustained precipitation – specifically, extensive snowfall in northern England and southern Scotland plus heavy rainfall in central England and Wales. This three-day period of sustained bad weather led to a surge in pre-faults on the UK’s electricity distribution networks.
Dr Clements explained, “The data from the UK’s 2024/25 storm season clearly shows a one-off event like a storm causes a rise in pre-fault levels - but nowhere near to the same extent as sustained rainfall. Storms are more violent and inflict physical damage, but rain can also seriously disrupt electricity supplies if operators overlook their distribution network.”
Dr Clements concluded by saying, “Fault-finding used to be slow and laborious, and customers would be off supply while you were doing it. But an operator who knows more precisely where to look for a pre-fault along a particular cable saves significant time and effort in locating and then fixing it. As a result, the operator avoids penalties from the regulator for customer minutes lost.
“The effects of climate change means that more extreme weather events are now increasingly commonplace in the UK and elsewhere - not only intense heatwaves but also storms, bouts of heavy rain and flash flooding.
“By using in-depth monitoring systems to identify pre-faults earlier, operators get in front of the problem and proactively address pre-faults caused by extreme weather conditions. They can mitigate or prevent entirely full outages before they occur to ensure people’s lights stay on in even the most challenging of conditions.”