A piece of electrical equipment found in hundreds of thousands of homes across the UK could pose a safety issue, according to industry documents seen by Scotland News.
Every home has a small box called a cut-out which links the mains electricity cable outside a property with the wires inside.
Guidance issued to meter operators highlighted concerns that an older version, made from black plastic, could overheat in some circumstances.
A retired engineer told the the units had caused fires – but an industry body said when installed correctly they do not pose a fire safety risk.
A cut-out, or service termination, is usually located near the electricity meter.
It contains a fuse to ensure electricity passes safely and efficiently into people’s homes.
Cut-outs are the property and responsibility of companies called Distribution Network Operators and must not be touched or changed by anyone without their permission.
The modern versions of these boxes are usually grey and made from glass reinforced polyester.
However, an older version made from a black plastic material called phenolic were installed in homes across the UK between the late 1960s and the early 1990s.
Gordon Mackenzie, who was a senior electrical engineer with Scottish Power Energy Networks until he retired in 2021, told Scotland that he lost “an awful lot of sleep” about these older units.
He said he started to notice in 2014 that black phenolic cut-outs were failing in similar ways.
He said the insulating material could break down, which allowed energy to flow between the different sections.
Mr Mackenzie said this led to a “catastrophic failure of the unit” and generated “an enormous amount of heat and energy” – which could cause serious fires.
He said failures of cut-outs were being reported on a daily basis, with about 90% of the most serious failures being made of black plastic phenolic.
“It’s something that weighs heavily on me because I believe as an industry we should be doing more to address this issue,” he said.
Mr Mackenzie has been attempting to raise awareness about the issue for more than a decade.
He wants a replacement programme to be introduced, starting with the properties where the most vulnerable customers live.
Scotland News has been unable to obtain any data on how many fires have started in these units – but we have seen industry documents suggesting there are safety concerns.
Guidance issued to the industry in 2021 says that “a potential safety issue” has been identified with black plastic cut-outs made from phenolic material and installed across the UK between 1967 and 1992.
The Meter Operation Code of Practice Agreement says the plastic casing can “in some circumstances become conductive leading to a risk of electric shock and/or excessive heat”.
Scotland News has also seen an internal Scottish Power Energy Networks document from 2021 making the case to replace the older black plastic cut-outs with newer grey glass reinforced polyester ones.
It states there had been “numerous” failures in the last 10 years with the “vast majority” centred around the black plastic cut-outs.
The document says it is seeking to reduce the “significant public safety risk” associated with these.
Safety ‘the highest priority’
Scottish Power Energy Networks did not directly respond to questions about this document.
In a statement, it said: “Health and safety is a core value for SP Energy Network and is intrinsic to the work we undertake on a daily basis.”
The Energy Networks Association (ENA), which represents the country’s network operators, said cutout failures were very rare.
We asked the ENA to tell us how many defects had been detected involving black plastic cut-outs. However, it did not give us that information.
Scotland News understands as part of ENA’s regular schedule of safety testing, a review of cut-out equipment performance and maintenance is being considered.
A spokesperson said: “Network operators make safety the highest priority in every aspect of their work and the UK is internationally recognised as having one of the most resilient and safe energy systems.
“Cut-outs, when installed correctly by a qualified electrical engineer, do not pose a fire safety risk in the UK.”
