The Norwegian Society of Electrical- and Automatic Control (NFEA) has published a new guide for the use of personal protective equipment (PPE) for arc flash hazards. Unitech Power Systems has contributed to the development of the guide together with Conoco Phillips, Equinor and Aker BP. The guide can be purchased from NFEA.
Arc flash is and will be a highly relevant risk in electrical installations, especially in installations with high short circuit fault levels. Statistics from The Norwegian Directorate for Civil Protection (DSB) shows that arc flash, and arc flash with subsequent damages, constitute 12.3 % of the reported damages in the period from 2010 to 2020. Arc flash incidents are usually associated with longer work absence and larger equipment damage than electric shocks.
In the latest revision of Elsikkerhet (Elsikkerhet 93 – a Norwegian annual magazine which reports electrical injury statistics, rules and regulations) an example is described in which only coincidences prevented a fatal injury. Also, an example of an arc flash incident with 4 weeks absence from work is described. The Norwegian Petroleum Safety Agency (PTIL) has also investigated two large incidents in industrial installations, in which arc flashes have caused large damages (see Related links).
A method of quantifying the risk for arc flash incidents is to perform an arc flash calculation. Arc flash calculations differ from ordinary short circuit calculations by also considering the reduced arcing current due to the impedance in the arc, as well as including the fault clearing times of the protection devices (relays and circuit breakers).
The result from an arc flash calculation is an incident energy in the unit cal/cm2, which can be used to select PPE, and which establishes basis for further risk reducing measures.
Risk management is a mandatory activity for all work in electrical installations. Arc flash calculations are a great aid in performing such risk management in installations with high short circuit fault levels, and also in installations with low short circuit fault levels, to ensure correct assessment of the risk. Before buying heavy and bulky PPE one should also investigate if other measures can be implemented to reduce the available arc flash incident energy.
Unitech Power Systems performs arc flash calculations for our clients frequently, for small and large installations, from 48 V DC battery installations up to 50 kV switchgear. Most calculations are made for 11 kV, 690 V and 400 V voltage levels, where the short circuit fault current levels can be especially high, combined with frequent activity in the installation. We perform calculations according to the latest standards (IEEE and IEC) and best practice on the subject matter.
If you need assistance to establish the foundation for the arc flash calculations, such as short circuit calculations and protection coordination studies we will also help with this. When the arc flash calculation is made, we will review the results and propose methods for reducing the incident energy in case it is particularly high. We have long experience with risk reducing measures and will propose measures jointly with you as our client.
The arc flash calculation results are also used to order warning labels for labelling switchgear. If required, we also assist in producing arc flash warning labels via our sub-supplier. The arc flash warning labels are designed according to The Workplace Regulations (arbeidsplassforskriften), NFPA 70E, and by use of ISO standardized formats.