CALCULATING INCIDENT ENERGY

By Rémi Hallé, P.Eng. Electrical Engineer, BBA

Over the last few decades, arc-flash hazards have been a significant concern for many electrical workers and employers. Many methods have been developed through the years to assess incident energy. The most common is that of the IEEE 1584, Guide for Performing Arc-Flash Hazard Calculations. These equations have remained the same since the standard was first published in 2002. Based on the results of more than 1,800 tests, the 2018 edition of the guide provides new formulas that are both more accurate and more complex. These formulas also take more parameters into account now, including the conductor orientation at the arc’s location and the compartment enclosure dimensions where the arc occurs.

 
2002 VS. 2018 EDITION: WHAT PARAMETERS TO USE

Given its complexity and need for more parameters, before using this new method for first time, it is important to understand the differences in results compared to the 2002 edition. First, should users of the 2018 edition expect higher or lower values for the same piece of equipment? Second, how will a parameter error affect the results? Some parameters required by the 2018 edition, i.e., the gap, the conductor orientation or the enclosure dimension, can vary a lot for the same piece of equipment or even in the same compartment. It might not be worth spending a lot of time and resources to get precise parameters; a standard value may be enough. On the other hand, standard values may not be correct and may lead to a significant incident energy error. It is important to determine which parameters need to be accurate.

UNDERSTANDING PARAMETER IMPACTS

The complexity of the model must reflect industrial realities: the expert must select, among the proposed parameters, those that are most representative of, or detrimental to, the actual installations and the work to be carried out on these installations. There are multiple software programs available on the market to perform incident energy analyses. Default values are not necessarily the most appropriate; it would depend on the application. It is still up to the engineer to use the proper parameters and understand their worth. A failure to understand the impact of a single parameter may lead to workers being exposed to higher than expected incident energy. For more details about the differences between the IEEE 1584 2002 and 2018 editions and the impact parameters can have on incident energy results, refer to this BBA white paper.

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