# Incident Energy Analysis Estimates Arc Flash Potential Risks

#### By R.W. Hurst, Editor

Conducting an incident energy analysis protects workers from arc flash hazards. The method provides a comprehensive and accurate estimate of the incident energy and can guide the appropriate PPE selection. Arc flash labels and the PPE categories method are other approaches that can help organizations protect their workers from arc flash risks. In addition, by incorporating an arc flash study into an electrical safety program, organizations can promote a safety culture and protect their workers from the hazards of arc flash events.

What is an Incident Energy Analysis?

It is a critical tool for identifying and mitigating the risks of arc flash hazards. However, before diving into the method, let's define incident energy. Incident energy is the thermal energy per unit area generated on a surface exposed to an arc flash event. It is typically measured in calories per square centimetre (cal/cm2) or joules per square centimetre (J/cm2). The incident energy is directly proportional to the magnitude of the fault current, the duration of the fault, and the distance between the worker and the arc source.

Conducting an incident energy analysis protects workers from arc flash hazards. The method provides a comprehensive and accurate estimate of the incident energy and can guide the appropriate PPE selection. Arc flash labels and the PPE categories method are other approaches that can help organizations protect their workers from arc flash risks. In addition, by incorporating an arc flash study into an electrical safety program, organizations can promote a safety culture and protect their workers from the hazards of arc flash events.

What is an Incident Energy Analysis?

It is a critical tool for identifying and mitigating the risks of arc flash hazards. However, before diving into the method, let's define incident energy. Incident energy is the thermal energy per unit area generated on a surface exposed to an arc flash event. It is typically measured in calories per square centimetre (cal/cm2) or joules per square centimetre (J/cm2). The incident energy is directly proportional to the magnitude of the fault current, the duration of the fault, and the distance between the worker and the arc source.

What is the Incident Energy Method?

The incident energy analysis method is an industry-standard approach that provides a comprehensive and accurate estimate of the incident energy and can guide the appropriate PPE selection. One such method is the IEEE 1584 Guide for Performing Arc-Flash Hazard Calculations, which comprehensively calculates a piece of equipment's incident energy and arc flash boundary. The governing body mandates the method in NFPA 70E standard for electrical safety in the workplace.

To calculate the incident energy of an electrical system, the IEEE 1584 method requires specific inputs, including the maximum available fault current at the point of interest, the clearing time of the overcurrent protective device, the distance between the worker and the arc source, the configuration and type of equipment, the type of grounding system used, the working distance of the worker, the duration of the arc flash event, and the protective clothing and equipment worn by the worker. The incident energy can be expressed in cal/cm2, and the arc flash boundary can be expressed in feet or meters. The incident energy level is also expressed in ATPV, which is expressed in incident energy with the units cal/cm2.

When using this study method, we must consider the arc flash boundary, which is the distance from the arc source within which a worker is likely to receive second-degree burns from the thermal radiation of the arc flash. The arc flash boundary is calculated based on the incident energy and can be expressed in feet or meters. Therefore, the arc flash boundary is essential when developing an electrical safety program and implementing protective measures.

Arc Flash Labels and PPE Categories

Arc flash labels are required by the National Fire Protection Association (NFPA) 70E standard and must be affixed to all electrical equipment that poses an arc flash hazard. Arc flash labels provide information on the incident energy, the required level of PPE, and the safe approach distance. The nameplate of an arc flash event should also include notes from the NFPA 70E tables for electrical safety in the workplace.

The PPE categories method is another approach to selecting appropriate PPE based on the incident energy level. The PPE categories method uses a table that correlates incident energy with four PPE categories, ranging from 1 to 4, with Category 4 offering the highest level of protection. The specific requirements for wearing PPE are expressed in incident energy with the units cal/cm2.

Incident Energy Analysis and Electrical Safety

Conducting a study is essential to an effective electrical safety program. Identifying the hazards associated with an electrical system can help reduce the risks of arc flash events and minimize the potential for injuries and fatalities. The method provides a comprehensive and accurate estimate of the incident energy and can guide the appropriate PPE selection. Incorporating an arc flash study into an electrical safety program can promote a safety culture and protect workers from the hazards of arc flash events.

The arrangement of an arc flash event is unpredictable, and tasks are not listed, making this kind of investigation necessary for ensuring workers' safety. By accurately calculating an electrical system's incident energy and arc flash boundary, workers can be protected from the hazards of an arc flash event. Therefore, the method is essential to electrical safety programs that can help organizations promote safety and protect their workers from arc flash risks.

How is it Calculated?

An incident energy analysis is performed using industry-standard methods and formulas to determine the incident energy of an electrical system. One such method is the IEEE 1584 Guide for Performing Arc-Flash Hazard Calculations, which comprehensively calculates a piece of equipment's incident energy and arc flash boundary.

The IEEE 1584 method requires the following inputs:

• The maximum available fault current and clearing time at the point of interest
• The clearing time of the overcurrent protective device
• The distance between the worker and the arc source
• The configuration and type of the equipment
• The type of grounding system used
• The working distance of the worker
• The duration of the arc flash event
• The protective clothing and equipment are worn by the worker

Using these inputs, the method estimates the incident energy in cal/cm2 or J/cm2. The incident energy can be used to determine the appropriate level of PPE needed to protect workers from the hazards of an arc flash event.

When using the method, we must consider the arc flash boundary, which is the distance from the arc source within which a worker is likely to receive second-degree burns from the thermal radiation of the arc flash. The arc flash boundary is calculated based on the incident energy and can be expressed in feet or meters. Therefore, the arc flash boundary is essential when developing an electrical safety program and implementing protective measures.

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