Calculating Arc Flash Hazards / Currents

1. Click Arc Flash.
2. Click Fault Bus(es). The program displays the arc flash boundaries (AFB), incident energies, and recommended personal protective equipment (PPE) for operation near the energized buses in the system. For example, a PPE requirement of three (3) is recommended (based on IEEE 1584) for any person working within 18 inches of energized SWG‑4.

Figure 1: Arc Flash Results on the One-line

Fault Interface

When EasyPower analyzes arc flash hazards, the program determines the theoretical arcing current for each faulted bus. This information is then used to calculate the hazard for each faulted bus.

In EasyPower, different methods are available to fault buses while in the Short Circuit focus:

• Click Fault Bus(es) without selecting any bus. This runs a batch fault on all the buses in your system. This provides arc flash hazard results for all buses.
• Double-click on a single bus to fault a bus.
• Select a bus or multiple buses (so they turn green) and click Fault Bus(es). To select a single bus, click with the left mouse button. To select extra buses, click on each bus while pressing SHIFT.

Unbalanced Fault Types

Three-phase fault currents are typically used for the arc flash analysis. The IEEE-1584 equations indicate that these provide conservative arc flash results for most systems. By default, the program does not enable unbalanced fault arc flash calculations. You can perform unbalanced arc flash fault through advanced options. See Arc Flash Hazard Options for more information.

Arc Fault Currents

When you click Arc Flash, all calculations automatically default to ½ cycle momentary results. This is based on the assumption that the arc flash is initiated by user actions (screw driver, dropping tools, and so on) and not random insulation breakdown leading to a longer-term arcing fault. This provides the most reasonable and conservative results for the initial arc blast. You can also calculate arc flash using Interrupting and 30 Cycle currents.

Another option is the Integrated method. The Integrated method takes into account the decreasing currents from motors and generators and also from multiple sources being switched out through protective devices tripping. The Integrated method is the closest to a realistic scenario.

Arc fault current can be set in Short Circuit Options on the Arc Flash Hazard Options tab through the Calculate Arc Flash Using setting.

More Information