Arc Flash Hazard Tab

You can select any of the following standards for calculation method.

• IEEE 1584
• NFPA-70E D.2, D.3 +
• V7.0 Enhanced
• V6.0 Enhanced

The IEEE 1584 equations are applicable up to 15kV. Above 15kV, the program uses the Ralph Lee method, and the distance “X’ factor and the gap from the library do not apply. This method has the distance exponent of 2.

Worst-Case Arc Flash Hazards

EasyPower obtains the arcing time from the upstream protective device of the faulted bus. The program uses the coordination feature PowerProtector™ to calculate the trip time for the estimated fault current passing through the protective device. This is the most accurate method. This option works only if you have the PowerProtector™ feature included in your EasyPower software.

Select one of the options to evaluate the arc flash hazard results for any bus in the following ways:

• Including Main: This option yields the results for fault on the bus bar itself. If a main breaker or fuse protects the bus and this breaker or fuse is connected to the bus, then the arcing time would be equal to the trip time for this main device. If a worker is working on the bus or on the load side of the main breaker/fuse, then this option of output applies. However, this option of output should not be used if energized work is required on the line side of the main breaker/fuse.
• Excluding Main: This option yields the results for fault on the bus bar excluding the tripping effect of the main breaker. This option of output is applicable to energized work on the line side of the main breaker of the bus. The remote upstream trip device is used to calculate the arcing time.

Note: Panels typically have the main breaker, bus bar and feeder breakers housed inside the same enclosure. Opening the front cover would expose a worker to arc on the line side of the main breaker. To simulate this hazard, select the Excluding Main option, since the device to interrupt faults would have to be an upstream device.

• Both (Incl & Excl Main): This option yields the results for fault on the bus bar as well as on the line side of the main breaker/fuse, provided the bus has a main breaker/fuse attached on the upstream side.
• Detailed: This option evaluates the results for the bus bar as well as the load side terminals of all protective devices attached to and downstream from the bus.

IEEE 1584 recommends using two scenarios – one with 100% of estimated arc current and the other with 85% of estimated arc current. This is due to the fact that arc currents may be random and usually vary by some proportion about the estimated value. For inverse-time over-current characteristics of protective devices, the arcing time is greater for smaller currents than it is for larger currents. Since the incident energy of arc faults is more sensitive to arcing time than it is to arc currents, it is necessary to obtain a more accurate arcing time. IEEE 1584 proposes taking 85% of the initial estimate of the arc current.

EasyPower enables you to consider two scenarios of arc currents. EasyPower calculates both scenario and automatically reports the worst case of incident energy, thus providing conservative results.

The IEEE 1584 recommended 100% and 85% of arc current are default values. You may change these ratios by typing in the fields or using the buttons to increase or decrease the values.

When 100% or the upper value yields greater arc flash incident energy, then the text results are displayed in black in the Arc Flash Report spreadsheet. When 85% or the lower value yields greater incident energy, the text is displayed in pink.

The Max Time is the maximum time that the program uses to calculate the incident energy. If the trip time calculated as per device TCC is less than the specified maximum time, then the device trip time is used. If the device trip time exceeds the specified maximum time, then the Max Time value is used. The default maximum time is 1000 seconds.

Specify the fault current used during arc flash calculations. Select between Momentary, Interrupting, and 30 Cycle fault currents or the Integrated method.

See The Integrated Method for more information about this method.

You can select the units for working distance from any of the following. This affects the results such as arc flash boundary as well.

• Inches
• Feet
• Inches/Feet: Displays results in both inches and feet.
• mm
• Meter
• mm/Meter: Displays results in both mm and meters.

You can specify separate working distances for open air and enclosed space. Select the appropriate choice to view or edit the values in the spreadsheet. Typically for medium voltage, switches and fuses at open air may be operated from a greater distance.

You can specify whether you want incident energy displayed in calories or joules per square centimeter.

Check this box to obtain a report of buses that exceed the arc flash threshold incident energies specified in the options. You can specify any incident energy as the threshold for various voltage levels by typing in the values in the spreadsheet in the Arc Flash Hazard options. All equipment exceeding the hazard thresholds will be displayed in red on the one-line.

For every voltage level you can specify the threshold incident energy. Equipment with incident energies exceeding the threshold values will be highlighted in red in the one-line output and they will be reported in the Arc Flash Threshold Report. This provides instant notification of a danger condition. All equipment with incident energies exceeding the threshold values are displayed in red on the one-line.

For every voltage level, you can specify up to five working distances for which the incident energy will be provided in the Arc Flash Report. In the one-line output, results will be shown only for the shortest working distance, which has the highest incident energy.