The fault in question is from broken protected earth and neutral (PEN) conductors, which are typically used to make a circuit via exposed metalwork such as gas, water, and oil pipes.
These conductors are used on the Protective Multiple Earthing or PME (TN-C-S) network, which was introduced in the 1970s 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”.
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Head of technical regulations at the IET, Mark Coles, explains: “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, undervoltage, neutral current diversion, the risk of electric shock, and in some cases, fire.”
PEN conductors
IET suggests rise in number of incidents correlates to the increase in the number of charge points
It has been found that the PEN conductors are “particularly susceptible to wear and tear, damage, corrosion, and deterioration across an aging PME network”. IET suggests that the rise in the number of incidents also correlates to the increase in the number of electric vehicle charge points and heat points, which could put additional strain on the PME network. Ultimately, this could result in more fire-related incidents.
As reported by IET, if the PEN conductor fails, it presents a shock hazard and a significant build-up of heat from the exposed metalwork, which could lead to a fire.
An additional concern is the challenge of identifying a fault with the PEN conductor in the first place, with IET noting that 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”. This suggests that more training information and support from the industry may be required.
Energy Networks Association
IET argues that one PEN failure could affect up to 50 properties at a time
A spokesperson for the Energy Networks Association (ENA) said that the number of broken PEN conductors is “relatively low compared to the actual amount of overhead lines and underground cables on the networks nationally.” However, IET argues that one PEN failure could affect up to 50 properties at a time, which could potentially mean thousands of properties each year.
Electrical Safety First (ESF), a charity dedicated to electrical safety, reports that 10% of broken PEN conductors lead to injury, suggesting that further investigation into their safe use is needed. Technical director for the ESF, Martyn Allen, explained that PEN conductor faults “can and do cause damage to electrical equipment but also present a serious risk of electric shock and fire”.
“The increase in the 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,” he added.
