Predicting let-through arc-flash energy for current-limiting circuit breakers

IEEE 1584, "Guide For Performing Arc Flash Incident Energy Calculations," provides a method to conservatively predict the incident energy let-through by over-current devices based on the device\´s time-current-curve or tested transfer functions. Additional testing by various manufacturers shows that current-limiting circuit breakers operating in their instantaneous current-limiting range perform significantly better than the IEEE Time-Current Curve-based model predicts. The authors will present an analytical method to estimate incident energy from published circuit breaker let-through curves. The method will provide a conservative, yet better estimate of the actual performance compared to test data. This method can be used as part of hazard risk planning rather than the method described in IEEE 1584 or when the manufacturer does not provide an incident-energy transfer function based on tests.