Arc Flash Studies: Why and when do I need them?

Henderson Engineers outlines the purpose of an arc flash study

By Tracy Wagoner October 18, 2022
Courtesy: Henderson Engineers

What is an Arc Flash?

An arc flash is the rapid release of energy produced from an unintended arc fault (short circuit) between live parts or live parts to ground. The energy is released as heat and light collide (electrical explosion) and create a concussive pressure wave that can carry shrapnel. The resultant energy is measured in calories per square centimeter (Cal/cm2), or incident energy.

What is an Arc Flash Study?

An arc flash study, also called an arc flash hazard analysis or arc flash risk assessment, is a study that identifies arc flash hazards, estimates the likelihood of severe injury, and helps determine the additional protections (controls and personal protective equipment (PPE)) needed for a given electrical system/installation as defined in NFPA 70E: Standard for Electrical Safety in the Workplace. Simply put, an arc flash study provides information regarding the incident energy available at the electrical components/devices that personnel would be exposed to while maintaining or otherwise interacting with that equipment and helps determine safe approach distances and PPE for conducting maintenance work.

Why is an Arc Flash Study Required?

An arc flash study is required to understand the maximum amount of energy that could be release by equipment requiring maintenance. Additionally, an arc flash study can inform a designer on how to eliminate or reduce hazard risk. Without an arc flash study, the proper elimination, reduction, mitigation, and protection techniques cannot be known to create a safe work environment around electrical equipment and installations.

When is an Arc Flash Study Required?

Arc flash studies are a product of several codes referencing the requirement to provide a safe work environment for the personnel maintaining equipment. The requirement stems from standards such as Occupational Safety and Health Administration (OSHA), NFPA 70E, National Electrical Code (NFPA 70), and Institute of Electronics and Electrical Engineers (IEEE). In addition, some states, including Washington (WAC296-45-325), mandate the requirement for an arc flash hazard analysis to be performed.

As you may know, OSHA provides health and safety requirements for employers. The information represented in NFPA 70E is what OSHA bases its electrical safety standards on (CFR 29 Part 1910 and Part 1926). Employers are required by CFR Part 1910.132 to identify whether workplace hazards are present or are likely to be present; and protect their workforce from those hazards.

Electrical equipment and installations all have some level of risk associated with them – especially when these installations and equipment may be maintained or operated while energized. This can mean the operation of enclosed circuit breakers, testing and/or troubleshooting efforts, and any exposure to live parts during maintenance. CFR Part 1910.132 also requires that the employer verify the required hazard assessment has been performed with written certification. Understanding this helps you identify that there are hazards present, or potentially present, with any electrical installation. Pursuant to OSHA 1910.132, those hazards must be identified and labeled such that proper PPE can be determined. This is where NFPA 70E comes in.

NFPA 70E is titled “Standard for Electrical Safety in the Workplace.” Section 110.1 outlines the requirements for employers regarding electrical safety. It requires that “the employer shall implement and document an overall electrical safety program that directs activity appropriate to the risk of electrical hazards. The electrical safety program shall be implemented as part of the employer’s overall occupational health and safety management system when one exists.”

Section 130.5 provides information on both shock and arc flash hazard risks, including standards for identifying and quantifying the risks of both. It requires that an arc flash analysis be performed to determine the incident energy at the required working distance, known as the arc flash boundary, as well as the proper level of PPE that shall be used within the arc flash boundary. Section 130.5 also requires labeling on all equipment “likely to require examination, adjustment, servicing, or maintenance while energized…” The label must contain the following data: arc flash risk identification, severity of the risk, arc flash boundary and required PPE, among other requirements.

What is Required to Properly Perform an Arc Flash Study?

There is numerous software that can be utilized to perform arc flash studies, but the information required is quite detailed. The most important aspect of performing an arc flash study is having an accurate and detailed representation of the electrical installation to be analyzed. A majority of this information can usually be found in the existing as-built one-line documentation; however, field verification of conductor lengths should be performed to ensure the study reflects the as built conditions. If the existing documentation isn’t available, or is incomplete, then a field survey of the installation is required. The following information is needed to develop an accurate model:

  • Utility information
    • Operating voltage
    • Available fault current
    • Utility protective equipment at the point of service
  • Paralleled Source information, including multiple services, generators, or other emergency power systems.
  • Electrical equipment information
    • Manufacturer
    • Types
    • Sizes
    • Time/current settings
    • Short-circuit interrupting rating
    • Cable/conductor type, size, and lengths
  • Motors connected to the system
    • Horsepower rating
    • NEMA configuration
  • Transformer
    • Rating
    • Impedance values
    • Tap settings

Who Can Perform an Arc Flash Study?

Performing an arc flash study is considered “practicing engineering,” which in most jurisdictions requires a professional engineer license. As such, when an arc flash study is required, it must be performed by an entity which is actively licensed in the location of the project.

Henderson’s Arc Flash Mitigation Approach

The best way to handle any problem is to mitigate the risk of it occurring in the first place. Henderson Engineers has developed a tried-and-true process for mitigating the risk of arc flash, which decreases the risk of injury for building personnel.

The first step in the process is to de-energize the equipment. This is the most straightforward approach to eliminate the arc flash hazard. This process also includes completing safety measures like lock-out and tag-out. However, there are certain instances where de-energizing the equipment is not possible because of life-safety considerations, mission-critical uses, or costs related to downtime. In these instances, it is required to engage our highly skilled field personnel that can gather information while equipment is energized in a safe manner that protects human safety as well as the integrity of the electrical systems.

Another avenue for mitigation includes utilizing remote work. This includes racking circuit breakers (CBs), closing switchgear, and adding sensors remotely. Remote work naturally increases the distance of the arc flash boundary, which further improves personnel safety.

Practical safety measures can go a long way in protecting personnel from arc flash. Using proper (PPE) based on calculations is always recommended. Training and planning is highly important. Helping owners understand the cost of mitigating arc flash directly relates to safety and often goes a long way. Educating personnel and building owners on proper mitigation techniques empowers stakeholders to take charge of their own safety.

Case Study: Confidential Data Center

Outages at a confidential client’s data center have implications on the world of finance and economics. The client’s data center suffered a catastrophic failure due to condensation buildup in their primary switch gear. Local attempts to mitigate the issue before an arc flash in the electrical infrastructure were not successful. They turned to Henderson Engineers and Henderson Building Solutions for a design/ build partner. Our team was able to provide the best of both the design and construction worlds to the master planning process.

Henderson started with re-commissioning of the electrical infrastructure. Recommendations were made to increase reliability and fault tolerance. Due to the secure nature of the facility, many previous infrastructure improvements were created as one-offs and lacked integration. Henderson has been able to create consistency in infrastructure without compromising security, allowing the client’s on-site facilities team to maintain the equipment with ease. With Henderson’s expertise in documentation, system verification, and understanding of the client’s goals, this project has evolved into a long-term partnership with multiple projects.


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Original content can be found at Henderson Engineers.

Author Bio: Senior Electrical Systems Manager | Associate