Arc-flash incident energies and boundary distances can be calculated in a variety of ways. For example, you can use the equations from IEEE Standard 1584. The IEEE 1584 established nine-steps in the arc flash hazard analysis process, namely:

The data needed for an arc flash hazard analysis is similar to that needed for a short circuit study. It's important to model the system in detail to get a reasonable assessment of the arc flash hazard. In most cases, this means collecting all the data needed to build a one-line diagram. [ more...]

The collected data is used to calculate available short-circuit currents at all critical points in the facility electrical system. Using the results from the short-circuit analysis and the settings of the protective devices, corresponding fault clearing times will be determined.

Calculate the bolted fault currents from the data collected in step 1 and step 2 above. The short circuit calculator presented on this web-site is offered in effort to satisfy the need for a convenient, comprehensive method of calculating short circuit currents.

The bolted fault current calculated for each point in the system represents the highest fault current expected to flow to any short circuit. In the case of an arcing fault, the current flow to the fault will be less, due to the added impedance of the arc. It's important to adequately predict these lower levels, especially if the overcurrent protective devices are significantly slower at these reduced levels. Such situations have been known to provide worst case arc fault hazards. The IEEE 1584 based online calculator will determine the arc fault currents based on the bolted fault current, system voltage and the equipment configuration.

The IEEE 1584 based online calculator offers guidance on using the time-current curves of overcurrent protective devices in various scenarios.

Factors such as bus gap and voltage affect arc energies and are required for IEEE 1584 equations. A table is provided with typical bus gaps for various equipment up to 15kV. [ more...]

Typically, this is assumed to be the distance between the potential arc source and the worker's body and face. Incident energy on a worker's hands and arms would likely be higher in the event of an arcing fault because of their closer proximity to the arc source. Typical working distances for various types of equipment are suggested in a table.

The calculator will perform the analysis based upon voltage level, the overcurrent protective device operating time and the equipment configuration.

The calculator will solve for a distance at which the incident heat energy density would be 1.2 cal/cm² (or 5.0 joules/cm²).

Calculations made using these guidelines are expected to be accurate because they are based on a large number of tests. However, there is no 100% accurate method for determining the degree of exposure that workers may face. The equations given in IEEE Std. 1584 are based on experimental 208V to 15kV laboratory tests. Three sets of equations are provided for the three distinct voltage ranges: 208V to 600V; 1kV to 15kV; and above 15kV. The actual radiated energy could be higher than the values yielded from the IEEE 1584 equations. The environment in which the arc takes place affects the arc-flash energy level. Factors like humidity, contaminants, temperature, enclosure type, and material consumed in the arc will affect the radiated energy level. In addition, other factors like power factor, the length and impedance of the arc, and the duration of the arc also come into play.

Our calculator calls for you to enter the fault level, voltage, clearing time, the equipment configuration and distance from an expected arc to the worker. It then calculates the incident energy level and boundary distance for this specific location on the system. You would use this data to create the labels required to be placed on the electrical equipment.