The truth about storm-related electricity faults

With the UK weather, electricity networks face a constant challenge to prevent outages from storm-related faults – sometimes as many as 100-200 per day. Dr David Clements, our Data Analytics Manager, explores storm-related outages and explains how our permanent monitoring equipment can detect pre-faults, their location, and assist network operators in proactive repair work.

Firstly, let us clarify the difference between a fault and a pre-fault.

A pre-fault is a short duration spike in current, caused by a breakdown of insulation on the feeder with the current returning to a normal level after. A fault, however, is a higher energy event where the fault current persists until protection operates to clear it, which results in an interruption to the customer supply. The graphs below illustrate what this may look like:

Now we’re clear on the difference between a pre-fault and a fault, what causes them?

Faults can be caused by numerous things such as insulation breakdown, third party damage, thermo-mechanical effects, and moisture ingress – which is a key risk during adverse weather. 

Rainfall and precipitation in the UK, on average, can be as high as 130mm per month in the winter and between 70mm-90mm in the summer. In addition to heavy rainfall, storms introduce more volatile and challenging weather to the electricity networks of the UK.

When we think of rainfall and storms impacting electricity networks, we envision lightning strikes and heavy gales bringing down power lines and pylons, but damage is also done underground. Heavy rainfall that settles in one spot filters through the ground and into the electricity lines below, causing faults and outages in the network and the substations that feed homes and businesses.

Storm Babet, which hit the UK in October 2023, examples this. Our fleet of 19,000+ VisNet Hubs and Guard devices saw more than 10,000 pre-fault events across 24 hours, indicating widespread electrical disturbance. These events indicate damage to underground cables that will inevitably lead to future outages. To visualise the surge in pre-faults, the chart below demonstrates just how severe the spike is during adverse weather:

To prevent pre-faults from becoming full faults that lead to customer outages, you must locate the pre-fault to perform repair or restoration work. To do this efficiently, waveform capable monitoring equipment must be installed, such as the VisNet Hub.

The VisNet Hub is an LV monitoring system that provides real-time network visibility, allowing substations to identify the location of pre-faults.

Adverse weather is unavoidable in the UK, meaning that electricity networks and lines will always be vulnerable. A complete monitoring system will allow you to take a proactive approach to pre-faults, reducing the number of customer outages and increasing the quality of your service. Outages result in costly penalties and complaints, and repair work on full faults are more expensive than proactive work on a pre-fault.

For more information on VisNet and the VisNet Hub contact one of our experts.