Advanced Arc Flash Options

Use IEEE 1584 equations for current limiting fuses to determine incident energy. This method calculates the let through arc flash incident energy based on bolted fault currents and UL class of fuse. Equations are available for classes L and RK1. This is applicable only for low voltage systems. The fuse equations are effective only when the fault current is high compared to the minimum fault current required for current-limiting. When the fault current is well below the current-limiting range of the fuse, the standard arc flash equations are used. When the 1584 CL Fuse Calculations are used for any bus, the Arc Flash Hazard Report shows the bolted fault current but not the arc current and the trip times, since these values are not used to determine the incident energy.

Note: The IEEE 1584 CL fuse equations provide incident energy at 455mm. The default low voltage working distance in the program is 18 inches (which is equivalent to 457.2 mm). Therefore, the results for 18 inches will be slightly different from the results for 455mm.

The boundary is at a distance at which the incident energy is less than or equal to 1.2 cal/cm². This is the default value. You can change it if necessary.

EasyPower supports two different methods for determining the remote current through protective devices during an arc fault:

• Equation: The arc current equation is used to calculate the remote currents. The equation is as per the Standard selected in the options and uses the equivalent bolted fault current through the device. This is the legacy method and is used for one-line files created in EasyPower/EasySolv 8.0.2.200 series or earlier versions.
• Ratio: The remote current is calculated by multiplying the bus arc current by the ratio of remote bolted fault current to bus bolted fault current. This method is the default method for new one-lines created.

This is the minimum trip time used for relays. The default value is 0.016s. If the relay trip time in a TCC shows less than this specified value, this minimum time is used in arc flash. One-lines created in versions previous to 8.0.2.305 will show a minimum relay trip time of 0.01 seconds. You can change this option.

This is the maximum number of buses the program will traverse upstream from the faulted bus to find the trip device. The default count is 12, to optimize for speed. You can increase the Traverse Count value if necessary. Examples of where it may be necessary to increase the Traverse Count include long distribution feeders with multiple taps, busways (bus ducts) with multiple bus plugs, underground distribution systems, and wind farms.

If this check box is selected, the PPE level is displayed on the one-line and the Arc Flash Hazard report.

If you have selected to show the PPE level, you can specify which standard you want to use to specify the level.

The levels are defined in the device library. See Defining PPE Levels for more information on customizing the levels.

Select the standard on which you want to specify approach boundaries. The options are:

• NFPA 70E 2018
• NFPA 70E 2015

NFPA 70E 2009 Annex D.8 Hazards

NFPA 70E 2009 Annex D.8 describes estimating the incident energy for overhead open air systems 1kV to 800kV. These calculations are based on open air phase-to-ground arcs.

Enables calculations for open air buses based on the Annex D.8 method.

• When Apply to >1kV is selected, all open air buses with voltage greater than 1 kV use this method of calculation.
• When Apply to >15kV is selected, only buses greater than 15kV use this method.

• Calculate based on NFPA 70E: Annex D.8 method specifies the working distances for various voltages. These working distances are used. The working distances specified in the Arc Flash Hazard Options or the Bus Data dialog or the work permit library are not used.
• Use EasyPower AF Options values: The working distances as per Annex D.8 are not used. The working distances used are as per the Bus Data if specified otherwise as per the Arc Flash Hazard Options.