How to mitigate risk with arc flash study project safety plans

Arc flash safety insights

• Conducting arc flash studies involves risks with live electrical equipment, necessitating comprehensive safety plans and strict adherence to NFPA 70E standards.
• Ensuring contractor safety during arc flash surveys requires the implementation of the hierarchy of risk controls
• Pre-survey safety training is crucial for mitigating risks associated with arc flash incidents.

An arc flash is a sudden release of electrical energy through the air that occurs when a high-voltage gap exists and a path to ground or lower voltage is introduced. This can result in an explosive discharge of light and heat, potentially causing damage to equipment and posing serious injury risks to personnel. According to industry statistics and research studies, there are an estimated five to 10 arc flash incidents daily in the United States that result in over 2,000 people receiving treatment each year for various levels of arc flash burns. In addition, they typically cause significant equipment failure, which leads to further system shutdown costs. Understanding arc flash risk can help mitigate these incidents and associated costs.

In the design and delivery of electrical engineering consulting services, it is common for clients to request an arc flash study for their facilities. This study helps to identify existing arc flash risks in different components of the electrical system and provides solutions to mitigate these risks for employees.

Risks in arc flash studies

One component of an arc flash study requires gathering existing electrical equipment information. Because the person gathering information may encounter live electrical equipment, there is an increased risk of an arc flash incident during this task. Both human error and equipment failure can cause an arc flash. Common human errors include accidental contact with live equipment, not following adequate safety procedures to operate live equipment, improper use of tools and wearing inadequate personal protective equipment (PPE) for the risk.

Figure 1: An example of damaged equipment from an arc flash incident. Courtesy: HDR

Safety requirements for outside contractors

Engineering companies that conduct arc flash studies often hire an electrical contractor to undertake the electrical survey. The Occupational Safety and Health Administration Safety Act of 1970  establishes that “Each employer shall furnish to each of his employees employment and a place of employment which are free from recognized hazards that are causing or are likely to cause death or serious physical harm to his employees.” This does not absolve a company hiring an electrical contractor to perform electrical work on their behalf from complying with safe work practices. Therefore, the hiring company still bears some responsibility for the safety of the contractor at the site. This must be communicated as a known hazard covered by NFPA 70E: Standard for Electrical Safety in the Workplace.

Creating an effective safety plan

The first step in any safety plan is to understand the intrinsic risks associated with gathering information for an arc flash study and identifying ways to minimize these risks. Once the risks are understood, there should be a discussion on a safety plan and mitigation steps.

Figure 2: Live electrical equipment has inherent risks for contractors and employees conducting arc flash studies. Courtesy: HDR

An effective arc flash safety plan should discuss the hierarchy of risk controls proposed in NFPA 70E, article 110.1 (H), ranked as follows:

1. Elimination: Physically remove the hazard.

2. Substitution: Replace the hazard.

3. Engineering controls: Isolate people from the hazard

4. Awareness: Increase visibility of the hazard

5. Administrative controls: Change the way people work.

6. PPE: Protect the worker.

In  many arc flash study surveys, the first levels of the hierarchy cannot be effectively achieved  without impacting the business operation. This situation is most noticeable on continuous operations businesses in industries like health care, utilities or manufacturing. Therefore, training must concentrate on the last three levels.

When addressing “awareness” of existing risks, the safety plan should use the facility’s existing one-line diagram to discuss each piece of equipment involved in the study. This helps identify any equipment that, by design, has the potential for a high arc flash incident and may elevate the risk to the contractor. For example, a low voltage substation in the main breaker section of the switchgear that is connected to the secondary side of the transformer may pose significant risks, unless additional protection schemes are in place.

The concept of establishing appropriate administrative controls within safety training involves discussing how to conduct the electrical survey safely. The topics include the tools to be used, appropriate clothing and methods for approaching each piece of equipment.

During general electrical work and, most importantly, while opening electrical equipment that could expose live parts, all tools used should have insulation and be rated for the work undertaken. Before commencing the survey, the contractor should inspect all tools to ensure they are in good working condition and that the insulation has not been compromised.

Regarding clothing and methods for approaching equipment, PPE provides a layer of protection for the contractor. PPE is listed as the last resource in the hierarchy of risk control since this does not eliminate or minimize the risk., but only provides limited protection for the arc flash incident energy. If it’s available, learning how to read the arc flash labels on electrical gear is the first step. Using methods from IEEE 1584-2018: Guide for Performing Arc-Flash Hazard Calculations or tables from NFPA 70E, contractors can determine the level of PPE required for the available incident energy listed on the label.

Figure 3: A contractor collecting information on the live switchgear. Courtesy: HDR

The label will also list the typical working distance and the arc flash boundary. The working distance is the space from a person’s face and chest to the prospective arc source, while the arc flash boundary is the distance at which the incident energy is limited to 1.2 cal/cm². This level of incident energy is considered an acceptable risk, as it likely will only create curable burns on exposed skin that are curable. Safety training should discuss ways for contractors to remain beyond the arc flash boundary when not conducting direct work with the electrical gear.

If arc flash labels are not available, the safety training should explore ways to eliminate or minimize the arc flash risk, per levels one to three of the hierarchy. This will require coordination with the facility to limit the impact of electrical system shutdowns.

Employers are required by law to provide a safe environment to employees and contractors. Implementing pre-survey safety training is the most effective way to protect contractors, assess potential risks and minimize the possibility of accidents.

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