Quantify the risk of arc flash for the right protection
Discover how to quantify arc flash risks in electrical and power work using calculation and assessment methods to choose the right protective clothing.
One of the most common questions we receive from our customers concerns the difficulty of quantifying the risk of an arc flash. That is, how strong the arc flash will be if it occurs and how great the probability is that it will happen. In this article, I present two different methods for quantifying the risk of arc flash and provide guidance on when each method should be used.
Two quantification methods: Calculate or assess
To address the challenge of quantifying the potential thermal arc flash energy, several standards and methods have been developed. NFPA 70E is the American standard for "Electrical Safety in the Workplace." This comprehensive standard covers many aspects of electrical work, including the use of the IEEE 584:2018 method for calculating thermal arc flash energy. The method is popularly called the "open arc test", but can also be applied in enclosed spaces. NFPA 70E additionally includes a method, NFPA 70E 130.7, for assessing the potential arc flash energy.
DGUV-I 203-077 is the German standard that corresponds to NFPA 70E in Europe. It supports carrying out risk assessments and calculating thermal arc flash energy. The standard, often referred to as the box test, also includes the BGI/GUV-I 5188 method for calculating this energy.
Below I give a brief description of each method type and how they can help you in your work to quantify the risk of arc flash. The methods differ in that one type is about calculating the risk, while the other provides guidance in assessing and estimating the risk.
Calculate with IEEE 1584: 2018 or BGI/GUV-I 5188
The IEEE 1584: 2018 and BGI/GUV-I 5188 methods provide guidelines for calculating the potential thermal arc flash energy that is released when an arc flash is triggered. These guidelines take into account several important parameters, including voltage, short-circuit current, breaker time, equipment configuration, working distance and whether the arc flash occurs in an open or enclosed space.
By entering the values of these parameters into the equations described in IEEE 1584: 2018 and BGI/GUV-I 5188, you can quantify the thermal arc flash energy and calculate the distance from the arc flash at which the energy is equal to or exceeds a specified value. In this way, you obtain a value for the thermal arc flash energy that may occur at your expected working distance – and can thus determine the distance from the arc flash within which there is a risk of burn injury, the so-called arc flash boundary.
Assess with NFPA 70E
NFPA 70E gives you concrete tools to assess the potential thermal arc flash energy in an electrical installation. This type of assessment involves comparing your installation with other typical installations and, based on this, obtaining a recommendation on which PPE category of arc flash protection should be selected.
A crucial part is to estimate the incident energy levels that arise if an arc flash occurs, assess the reach of the arc flash and evaluate the likelihood and severity of potential injuries.
There are also matrices that have been developed – among others by ESTI in Switzerland and certain leading companies – to enable a quick assessment of the thermal arc flash energy in an installation and to match your protective equipment to this with a specified safety margin.
Which method is best?
The calculation method is more accurate and therefore the best method. One of the major advantages of having calculated your arc flash risk is that you can then choose your protection level more precisely and thereby obtain a more comfortable and cost-effective system of protective clothing.
The assessment method is used mainly when the arc flash risk has not been quantified. One example might be when an electrician arrives at an installation for which the risk has not been calculated; he or she can then carry out an assessment in accordance with NFPA 70E and adapt the protection accordingly.
One disadvantage of this method is that it is more uncertain compared to the calculation method and can therefore result in the user wearing clothing that is unnecessarily thick and heavy in order to be "on the safe side". However, the assessment method is clearly much better than taking a chance and doing nothing.
By following the procedures described in NFPA 70E and DGUV-I 203-077, you can calculate and assess as well as manage the risk of arc flash – and thereby promote a safer working environment.
