Arc Flash Calculator - Incident Energy

By R. W. Hurst, The Electricity Forum

An arc flash calculator is a tool or software used to determine the potential incident energy, arc flash (AF) boundary, and personal protective equipment (PPE) requirements for electrical workers who may be exposed to AF hazards. AF is a dangerous and potentially fatal occurrence when an electrical discharge travels through the air between conductors, often resulting from insulation failure, accidental contact, or equipment malfunction.

The calculations are based on various factors, such as:

  • System Voltage
  • Available fault current
  • Arcing time
  • Equipment configuration
  • Working distance

Arc flash calculations are typically performed using one of two widely recognized methodologies: the IEEE 1584 standard or the NFPA 70E approach. Both methods provide guidelines for determining AF hazards and selecting appropriate PPE to protect workers.

Using one helps ensure the safety of electrical workers by providing essential information for risk assessment and mitigation. It also helps companies comply with regulatory requirements and maintain a safe working environment.

The software demonstrates AF hazard calculations and system changes' impact on energy levels and personal protective equipment Requirements (PPE) for AF Hazards. It is best designed to estimate incident energy levels and categorize arch flash hazards at any point in an electrical system. This special engineering software determines the fault clearing time for protective device (like electrical circuit breakers) settings. It can also calculate incident energy and flash protection boundaries (safe working distance from an explosion); document personal protective equipment (PPE) requirements; and prints custom warning labels, energized work permits, and diagrams with input data and calculation results. It also uses generous tolerances for utility, transformer, cable, and motor data to calculate the conservative minimum and maximum fault currents. It includes a validated library of protective device trip characteristics to provide accurate arcing time for the calculations.

Reducing the electrical energy delivered to the AF incident will reduce the amount of AF energy generated. This decrease in incident heat energy usually reduces the category of personal protective equipment (PPE) required, enabling personnel to work more easily and efficiently.

The software can be used to determine incident heat energy at a certain distance, and the category of PPE required. Enter the bolted fault current, choose a current-limiting fuse from the drop-down menu, and select "calculate." See cautionary notes prior to use.

Calculations are based on three-phase tests at 600V using a 20" x 20" x 20" box, as described in IEEE 1584 Guide for Performing Arc Flash Calculations. They determine the PPE required to protect against the effects of radiated heat and do not consider the effects of pressure, molten metal droplets, toxic smoke or plasma jets. Therefore, actual AF results could differ from those given here.

Software resources:

Arc Flash Hazard Calculator - IEEE 1584 Method

Arc Flash Hazard Calculator - Easy Power

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June, 2023