ARC FLASH FEATURE
GENERATING ELECTRICITY while staying safe
Global power generation company InterGen has improved safety levels at its Runcorn site by introducing the organisation’s Arc Flash Mitigation Programme. Ray Howarth, long term engineer at the Runcorn plant, explains how
I
nterGen is a global power generation company with presence in the
Netherlands, Mexico, the Philippines, Australia, as well as the UK - collectively generating 8,146MW of electricity. One of the company’s key priorities is the safety of its employees, contractors, visitors and the communities in which it operates, as well as a healthy and injury-free workplace. What’s more, the organisation also claims that safety is its most important performance metric. Nowhere is this claim better
emphasised than at InterGen’s Runcorn plant, Rocksavage Power Station, one of the three plants based in the UK. This plant is not only one of the cleanest and environmentally efficient facilities in the UK, but it has an excellent safety record, operating more than one million safe man hours without a lost time incident during the last five years. Howarth takes up the story, “To
maintain the consistent generation of electricity it is essential that the plant operates effectively and is commercially viable all the time. This level of operation results in ongoing maintenance work and it is this activity that potentially exposes our workers to higher risks and one that InterGen wants to mitigate as much as possible. The rule, throughout the organisation, is never to work on anything
Above: it is widely recognised that the higher the voltage of an electrical power system, the greater the risk for people working on or near energised conductors and equipment
above 1,000V live. ‘Live Working’ procedures are in place for lower voltages and when essential maintenance work must take place, a physical isolation or ‘air gap’ is required to maintain safety from the system. It is this particular procedure that poses an increased risk and one where a major hazard such as an electric arc flash could occur.”
UNDERSTANDING THE RISKS Electrical flashover or ‘arc flash’ is one of the most deadly and least understood hazards of electricity. Each year around 1,000 electrical accidents at work are reported and as many as 25 people die from their injuries. It is widely recognised that the higher the voltage of an electrical power system, the greater the risk for people working on or near energised conductors and equipment. However, arc flash can still cause devastating injuries, even at low voltages. An 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 resulting short circuit current will melt the conductors, ionise the air and create a conducting plasma fireball with temperatures in the core of the arc that can reach upwards of 20,000ºC. The risk of injury can extend beyond the immediate area.
/ ELECTRICALENGINEERING ELECTRICAL ENGINEERING | MARCH 2014 29 Arc flash injury can include external burns
to the skin, internal burns from inhaling hot gases and vaporised metal, hearing damage, eye damage such as blindness from the ultraviolet light of the flash, as well as many others. Depending on the severity of the arc flash, an explosive force known as an arc blast may also occur which can result in pressures of over 100 kilopascal (kpa), launching debris as shrapnel at speeds up to 300mps (a high speed train travels, on average, 85mps).
TIME TO TAKE ACTION Following arc flash incidents at a number of locations, InterGen senior management launched their Arc Flash Mitigation Programme across their facilities. The programme is designed to identify the potential risk to personnel from all items of LV and HV apparatus
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