- As incidents are often not reported, the real figure is likely to be much higher and each incident can affect fifty properties, meaning tens of thousands of properties are likely at risk in the UK.
- It was also a cheaper alternative to the traditional four-core and lead sheath cables.
- The charity says an urgent investigation is needed.
Over the past twenty years, an electrical fault type that puts the public in danger of fire in the UK has surged by more than eight times, prompting calls for openness from experts, as reported by ET.
Reports of broken PEN (protected earth and neutral) conductors increased from 57 in 2003 to 474 reports last year, according to a Freedom of Information (FOI) request.
As incidents are often not reported, the real figure is likely to be much higher and each incident can affect fifty properties, meaning tens of thousands of properties are likely at risk in the UK.
PEN conductors serve as both a protective earthing and neutral conductor and are used on the PME (TN-C-S) network, which was introduced as an alternative to TN-S and TT in the 1970s.
The PME network was intended as a self-monitoring system to improve safety and provide an easy indication if a fault were to occur with the combined neutral and protective conductor.
It was also a cheaper alternative to the traditional four-core and lead sheath cables.
When the PEN conductor fails, not only does this present a shock hazard but it generates a diverted neutral current, which can create a significant build-up of heat, as it typically makes a circuit via exposed metalwork such as gas, water and oil pipes.
Due to the characteristics of not only the PME system but also the water and gas services and other factors such as steel foundations and the older TT systems, it cannot always be easily identified that there is an issue with the PEN conductor.
The general public, homeowners and even skilled electricians may not know how to assess an installation correctly to identify that there is a potential problem with the PEN conductor.
Paul Meenan, a mechanical and electrical assets manager for the railway operator Trenitalia c2c, said: “broken PEN and diverted neutral currents are a growing challenge for the distribution operators”.
“We need more training information and support from the industry including transparency on this to ensure public safety.”
According to Meenan, electricians can measure diverted neutral current, which can indicate whether a PEN is likely to break in the future, as resistance on the network may be higher than expected.
District network operators (DNOs) are responsible for maintaining a safe supply.
“In the past five years, the six DNO companies serving Great Britain have spent around £12bn on measures that support increased reliability and resilience.”
The ENA also said the number of broken PENs was “relatively low compared to compared to the actual amount of overhead lines and underground cables on the networks nationally”.
However, one broken PEN incident may affect the region of 50 properties, meaning tens of thousands of properties could be affected every year in the UK.
The charity Electrical Safety First (ESF) has previously said that 10% of reported broken PEN conductors lead to injury.
The charity says an urgent investigation is needed.
Martyn Allen, technical director for the ESF, said incidents involving broken PEN conductors “can and do cause damage to electrical equipment but also present a serious risk of electric shock and fire”.
He added: “That’s why Network Operators are required to report broken PEN incidents to the HSE under the Electricity, Safety, Quality and Continuity Regulations 2002.
The increase in number of reported incidents is concerning but there are also reports that many incidents go unreported.
An investigation into reported and unreported open PEN incidents is needed so we can better understand the scale of the problem, the risk and the solutions needed.”
“On paper, PME is a reliable and robust method of distributing low voltage electricity. This is certainly true for new installations but, unfortunately, older parts of the network are failing due to the length of time the distribution cables have been in the ground. Corrosion of joints in the cables can result in the severance of the PEN conductor, leading to overvoltage, under-voltage, neutral current diversion, the risk of electric shock and, in some cases, fire,” he said.
The Health and Safety Executive and the Department for Levelling Up, Housing and Communities have both been approached for comment.
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