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Explains
The causes of arc flash
Robert Snodgrass, HM specialist inspector – electrical, controls and cyber security at the HSE, explains that arc flash is usually caused by inadvertent contact between an energised conductor such as a busbar or wire with another conductor or an earthed surface.
“When this occurs the resultant short circuit current can melt the conductors and produce strong magnetic fields that blow the conducting objects apart,” he says.
“The resultant fault current ionises the air and creates a conducting plasma fireball with arc temperatures that can reach upwards of 20,000 degrees centigrade at its centre.”
This will vaporise all known materials close to the arc immediately, and the energy emitted may ignite workers’ clothing and cause burns, or burn workers even without clothing being ignited. “Severe injury and even death can occur, not only to the persons working on electrical equipment, but also people located nearby,” Snodgrass tells Utility Week Intelligence.
Arc flash injury includes external burns, internal burns and intoxication from inhaling hot gases and vaporised metal, hearing damage, eye damage and blindness from the ultraviolet light of the flash, as well as many other devastating injuries.
Depending on the severity of the arc flash, an explosive force known as an arc blast may occur. This can create massive force, propelling molten metal and parts of equipment at speeds of hundreds of metres per second.
Is potential for arc flash increasing because of the electrification of the economy?
“You would have to say ‘yes’,” says Snodgrass. “My reasoning behind this is the increasing use of battery power, wind and marine energy, and solar power.”
Networks must take into account the potential for arc flash. Mark Dunk, head of engineering at the Energy Networks Association, which represents the UK’s electricity network operators, says they understand how to mitigate the risks of electrical flashover.
“The safety of our customers and employees is the highest priority for network operators. The UK energy system is one of the safest and most reliable internationally, and any safety risks are managed by an interlocking framework of safety systems.
“Arc flashes are a well-documented risk, and energy systems are run to minimise the chance of their occurrence. On the rare occasions when arc flashes may occur, including during types of repair or maintenance work on live infrastructure, network operators provide appropriate protective clothing with arc resistant properties, as part of a rigorous and well-established safe system of working.”
Experts agree, however, that consistent and complete wearing of this PPE is vital to safe working practices. HSE guidance should be followed at all times, they say.
Snodgrass, who specialises in the offshore sector, points out that injuries caused by arc flash are mercifully few and far between. “From an offshore perspective there have been many arc flash incidents but only two that have involved injury to personnel. One was in 2012 which involved significant injuries, and the other in 2021 which involved burns to the back of the hand.
“There have been no incidents that have resulted in death from arc flash in the UK offshore environment,” he points out.
Depending on the severity of the arc flash, an explosive force known as an arc blast may occur. This can create massive force, propelling molten metal and parts of equipment at speeds of hundreds of metres per second.
An electrical plasma arc can reach 20,000 degrees C
The causes of arc flash
Robert Snodgrass, HM specialist inspector – electrical, controls and cyber security at the HSE, explains that arc flash is usually caused by inadvertent contact between an energised conductor such as a busbar or wire with another conductor or an earthed surface.
“When this occurs the resultant short circuit current can melt the conductors and produce strong magnetic fields that blow the conducting objects apart,” he says.
“The resultant fault current ionises the air and creates a conducting plasma fireball with arc temperatures that can reach upwards of 20,000 degrees centigrade at its centre.”
This will vaporise all known materials close to the arc immediately, and the energy emitted may ignite workers’ clothing and cause burns, or burn workers even without clothing being ignited. “Severe injury and even death can occur, not only to the persons working on electrical equipment, but also people located nearby,” Snodgrass tells Utility Week Intelligence.
Arc flash injury includes external burns, internal burns and intoxication from inhaling hot gases and vaporised metal, hearing damage, eye damage and blindness from the ultraviolet light of the flash, as well as many other devastating injuries.
Depending on the severity of the arc flash, an explosive force known as an arc blast may occur. This can create massive force, propelling molten metal and parts of equipment at speeds of hundreds of metres per second.
Is potential for arc flash increasing because of the electrification of the economy?
“You would have to say ‘yes’,” says Snodgrass. “My reasoning behind this is the increasing use of battery power, wind and marine energy, and solar power.”
Networks must take into account the potential for arc flash. Mark Dunk, head of engineering at the Energy Networks Association, which represents the UK’s electricity network operators, says they understand how to mitigate the risks of electrical flashover.
“The safety of our customers and employees is the highest priority for network operators. The UK energy system is one of the safest and most reliable internationally, and any safety risks are managed by an interlocking framework of safety systems.
“Arc flashes are a well-documented risk, and energy systems are run to minimise the chance of their occurrence. On the rare occasions when arc flashes may occur, including during types of repair or maintenance work on live infrastructure, network operators provide appropriate protective clothing with arc resistant properties, as part of a rigorous and well-established safe system of working.”
Experts agree, however, that consistent and complete wearing of this PPE is vital to safe working practices. HSE guidance should be followed at all times, they say.
Snodgrass, who specialises in the offshore sector, points out that injuries caused by arc flash are mercifully few and far between. “From an offshore perspective there have been many arc flash incidents but only two that have involved injury to personnel. One was in 2012 which involved significant injuries, and the other in 2021 which involved burns to the back of the hand.
“There have been no incidents that have resulted in death from arc flash in the UK offshore environment,” he points out.
“On the rare occasions when arc flashes may occur, including during types of repair or maintenance work on live infrastructure, network operators provide appropriate protective clothing with arc resistant properties, as part of a rigorous and well-established safe system of working.”
Mark Dunk, head of engineering, Energy Networks Association
