How to better protect against electrical hazards in the workplace
Understanding arc flash safety can save lives.
- Know how an arc flash assessment is conducted.
- Understand the lockout/tagout procedure and how it is used.
- Identify when to use the NFPA 70E methods for arc flash personal protective equipment.
Arc flash insights
- To protect workers from arc flash hazards, commercial facilities should conduct safety assessments of their electrical systems.
- Without proper safety techniques and personal protective equipment, electric and arc flash hazards can pose strong risks to employees.
Electricity is beneficial in many ways, and electrical power needs to be respected. Walking into or near electrical enclosures and components is hazardous, even for qualified and experienced electrical workers. Electrocution can cause serious injuries or death. According to the latest U.S. Census of Fatal Occupational Injuries report, 152 workers died in 2021 due to exposure to electricity. In 2020, there were 126 deaths. Exposure to electricity can have a range of causes including direct contact with live wires, electrocution from faulty equipment and wiring or an arc flash event.
An arc flash event is an explosion of electricity resulting in very high air temperatures, pressure waves and noise. When electricity is conducted through the air, it is very hard to control. If someone accidentally gets in between the source of an electrical current and its intended path, a person can be exposed to an arc flash hazard.
Arc flash safety assessments
To ensure safety, commercial facilities should do assessments of electrical systems to protect employees and contract workers from arc flash hazards. The highest risk occurs when a newly installed electrical system is being turned on and tested. If there are any issues, they will become apparent once the facility is energized.
Most businesses and workers are familiar with the main government body overseeing workplace safety — the Occupational Safety and Health Administration (OSHA). It sets and enforces standards and regulations for electrical safety in the workplace, including Arc Flash Safety. Specific requirements for electrical safety standards for general industry workplaces are detailed in OSHA 29 Part 1910 Subpart S Electrical. The National Fire Protection Association works with OSHA to further electrical safety.
NFPA 70: National Electrical Code also provides industry guidance on designing and installing electrical equipment and systems correctly to be in compliance with OSHA regulations. The National Electrical Code provides these standards to protect and minimize arc flash hazards. So, how are these guidelines used when assessing a space?
When conducting assessments, companies like Lockwood, Andrews & Newnam Inc. (LAN) have a licensed professional engineer (PE) supervising the process. The PE oversees a team of engineers and licensed electricians. Electricians help establish safety protocols for data collection during field inspections.
During an assessment, engineering and design team members determine the characteristics of the electrical systems: the types, sizes and lengths of the wires, what pieces of equipment are connected to them and the type of panel being used. They create one-line diagrams to document and illustrate the electrical system, showing how all the components, panels and wiring are interconnected.
This information is then input into software to create a model that simulates different conditions in the system. The severity of potential hazards, such as arc flashes, can be determined by mimicking various scenarios in this way. Interconnections and switches can be turned on and off in the model to calculate the available energy in case of an arc flash. Different scenarios can also be modeled to assess whether the potential energy of an arc flash can be reduced, and recommendations can be made accordingly.
Reducing electrical hazards
NFPA 70E: Standard for Electrical Safety in the Workplace requires arc flash assessments to be done or re-evaluated every five years for commercial sites. These evaluations are done indoors, around buildings and outdoors in facilities like power, oil and gas and water treatment plants (see Figure 2).
It is essential for all team members to be trained in electrical safety and to maintain a safe distance from hazards. If a safe distance cannot be determined until the hazard is analyzed, safety should be the priority. To prevent accidents, everyone on the team must wear the appropriate personal protective equipment (PPE) when they are working near an energized electrical hazard. This protects them when opening panels, collecting data and taking pictures of wiring and circuit protection devices. NFPA 70E sets a minimum protection rating for PPE apparel based on the hazard encountered. Protective clothing typically comes in ratings, such as 4, 8, 25, and 40 cal/cm2. Each specific article of PPE clothing is manufactured according to standards set by the American Society for Testing and Materials (ASTM). (These standards are listed in NFPA 70E Table 130.7(C)(14) Informational Note: Standards For Personal Protective Equipment.)
When electrical equipment is in a safe working condition and de-energized, the hazard is reduced. When it’s not safe, it’s important to use a lock out/tag out procedure, where electrical equipment is physically locked and tagged to prevent operation (see Figure 3).
The tag describes the affected equipment or load, indicating that it has been electrically disconnected and is safe. An electrician will test for voltage to ensure the power has been de-energized. Engineers can then document the electrical equipment safely.
Arc flash PPE selection
To determine PPE requirements, NFPA 70E allows two methods: the incident energy analysis method and the arc flash PPE category method. The incident energy analysis method is a calculation procedure using modeling software to determine the required PPE needed for a specific electrical hazard. The arc flash PPE category method is used to determine the required PPE based on specific electrical hazard categories. Industry standards like NFPA 70E consider factors such as overcurrent protection devices, clearing times and fault currents.
As systems age, more stringent reviews are necessary, especially for electrical systems requiring upgrades and repairs. Calculations should be performed to determine the potential for an arc flash incident. Even in new buildings, conducting an electrical verification is advisable to ensure accurate protective device clearing times and fault currents. As an industry, electrical engineers aim to protect people and property from accidental or unintended consequences and arc flash safety is no exception. Engineers must never underestimate the hazard of electricity just because it cannot be seen.
Detailed and comprehensive arc flash hazard analyses are essential for well-reviewed and maintained electrical systems. Especially when dealing with electrical issues, knowledge of surroundings can protect engineers, facility employees and the public. In the end, designing and operating superior infrastructure protects everyone.