Arc flash protection is essential in any work environment with electrical equipment. Companies can create a safer workplace and reduce the risk of arc flash (AF) incidents by understanding the potential threats associated with electrical equipment and implementing appropriate measures to protect workers. This includes establishing AF boundaries, implementing AF mitigation solutions, and providing appropriate PPE. It is important to note that protecting workers from the dangers of AF incidents is an ongoing process that requires regular training, inspection, and maintenance to ensure continued effectiveness.
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In many industries, electrical equipment is a critical component of day-to-day operations. First, however, it is essential to recognize the potential threats associated with this equipment, particularly the risk of an AF incident. An AF is a sudden, explosive release of energy that occurs when an electrical current jumps across an air gap, producing high levels of heat, light, and pressure. AF incidents can cause serious injury or even death to workers and significant damage to equipment and facilities.
Understanding Arc Flash Protection
An AF threat is a term that describes the risk of an AF incident occurring in a particular situation. This threat is influenced by several factors, including the electrical system's voltage, the level of available fault current, and the time it takes for a circuit breaker to trip in the event of a fault. Generally, the higher the voltage and available fault current, the longer it takes for a circuit breaker to trip and the greater the arc flash threat.
The potential AF threat can be quantified using incident energy, expressed in calories per square centimetre (cal/cm2). Incident energy is a measure of the thermal energy that could be released during an AF incident. It determines the personal protective equipment (PPE) required to protect workers.
To help reduce the risk of AF incidents, the National Fire Protection Association (NFPA) in the United States has developed guidelines for establishing AF boundaries. These boundaries are intended to define the area around electrical equipment where workers may be exposed to an AF threat and are established based on the incident energy level of the equipment. There are three types of AF boundaries:
Limited approach boundary: This is the closest distance that an unqualified person may approach an energized piece of electrical equipment. This boundary protects workers who need to be trained or qualified to work on electrical equipment.
Restricted approach boundary: This is the closest distance that a qualified worker may approach an energized piece of electrical equipment without wearing appropriate PPE.
Prohibited approach boundary: This is the closest distance any worker may approach an energized piece of electrical equipment and is only permitted under certain conditions, such as when the worker is wearing appropriate PPE.
Arc Flash Mitigation Solutions
Several solutions can be implemented to reduce the risk of AF incidents, including:
Circuit breakers are devices designed to protect electrical systems from overcurrent conditions that could lead to an AF incident. By tripping when an overcurrent condition occurs, circuit breakers can help prevent the release of energy that could cause an AF.
Reducing voltage: By lowering the voltage of an electrical system, the potential AF threats can be reduced. This can be achieved using transformers or changing the electrical system's configuration.
Arc flash detection and mitigation systems: These systems are designed to detect an arcing fault and rapidly interrupt the power supply to the affected equipment before an arc flash can reach a hazardous level. The risk of an AF incident can be reduced by quickly isolating the fault.
Maintenance and inspection: Regular maintenance and inspection of electrical equipment while the equipment is de-energized is the safest approach before energizing equipment. This is essential to reducing the risk of AF incidents. Identifying and repairing potential threats before they become dangerous can greatly reduce the risk of an AF incident.
Personal Protective Equipment (PPE)
Personal protective equipment (PPE) is an essential component. PPE is designed to protect workers from the heat, light, and pressure produced by an AF incident and should be selected based on the incident energy level of the equipment.
Several types of PPE may be required, including:
Flame-resistant clothing: This includes shirts, pants, coveralls, and other clothing items made from materials resistant to ignition, melting, and burning. The clothing should be rated to withstand the incident energy level of the equipment being worked on.
Eye and face protection includes special protective glasses or goggles with side shields, face shields, or welding shields with appropriate shade numbers. The protection should be rated to withstand the incident energy level of the equipment being worked on.
Head protection: This includes hard hats with arc-rated face shields or hoods. The head protection should be rated to withstand the incident energy level of the equipment being worked on.
Foot protection includes protective shoes or boots with a steel toe and puncture-resistant sole. In addition, the footwear should be rated to withstand the incident energy level of the equipment being worked on.
Hand protection includes insulated gloves and leather protectors designed for electrical work. The gloves should be rated to withstand the incident energy level of the equipment being worked on.
It is important to note that all PPE worn must be arc-rated and tested to meet the relevant standards. It must be inspected and maintained regularly to ensure its effectiveness. Additionally, workers should receive training on the proper use and care of their PPE and the potential threats of AF incidents.