![]() When using a current-limiting fuse, how can you calculate the arc flash current when you know the short circuit current?Īrc fault currents can be estimated through various models, such as the method identified in IEEE 1584, Guide for Performing Arc Flash Calculations. With the new IEEE 1584-2018 model, it is now recommended that the let through current for the calculated arc fault current be used in the final incident energy calculation. During a flash hazard analysis, is it necessary to calculate arc fault current when using current-limiting fuses? For applications where the expected arc fault current would be lower than current-limiting threshold of these fuses, consider solutions discussed under Addressing High Incident Energy due to Low Fault Currents. Going to lower ampere ratings where load currents allow can also address these issues. Many times, the switch from Class RK5 fuses to Class RK1 or Class J fuses addresses the issue of lower fault currents. The key to acceptable arc flash mitigation is to apply the fuse where the expected level of arc fault current will be large enough to drive the fuse into current-limiting mode. ![]() Tests have shown that under most conditions, Class J, Class RK1 and Class T fuses can limit incident energies to low levels at typical working distances. I've heard that under certain conditions, current-limiting fuses can allow for high incident energies when the fault current is low. The NFPA 70E requires new arc flash labels to convey the results of any new arc flash study. Labels provide information about hazards that workers need to use correct safety procedures and PPE. Yes. The IEEE 1584-2018 has the most current model and equations. Do I need to change my arc flash labels if calculations with the new IEEE 1584-2018 model are different? IEEE 1574-2018 model was developed from further testing organized by the IEEE/NFPA Collaborative Arc Flash Reseach project with the main purpose of adding enough data to add additional test setups with new electrode configurations. The 2002 release contained one electrode orientation and two configurations. IEEE 1584 was originally released in 2002 and became the premier standard for arc flash hazard arcing current, incident energy, and arc flash boundary calculations. Why has the guidance on arc flash calculations changed in IEEE 1584-2018? What is meant by the phrase “exposed to the arc flash hazard” in NFPA70E?Įach task performed in the electrical working zone has been analyzed and the likelihood of an arc flash injury maybe present. What is meant by electrode configuration? How do I choose one?Īs part of the data for the arc flash calculation, the equipment conductor configuration that most closely resembles the actual electrode configurations need to be identified. Have a question you don't see answered? E-mail us at or call Technical Services at 97. Here are some common questions regarding current-limiting fuses, hazard analysis and safe work practices, along with answers provided by Mersen engineers.
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