Arc flash hazards represent one of the most significant electrical safety risks faced by personnel working on or near energised electrical equipment. Unlike electric shock, which is often localised to the point of contact, an arc flash event can release enormous amounts of thermal energy, pressure, sound, and molten metal in a fraction of a second.
The consequences can be severe, including life-changing injuries, equipment damage, prolonged outages, and significant financial losses.
Despite the seriousness of the hazard, arc flash assessments are often misunderstood. Many organisations focus primarily on the labels attached to switchboards and motor control centres, viewing them as a compliance requirement rather than the outcome of a detailed engineering study.
In reality, the arc flash label is only the final deliverable. The true value lies in the engineering assessment used to determine the incident energy exposure, safe working distances, personal protective equipment (PPE) requirements, and opportunities to reduce risk.
This article provides an overview of arc flash studies, explains when they should be performed, and discusses why both existing and new electrical installations should be assessed.
Understanding Arc Flash
An arc flash occurs when electrical current leaves its intended path and travels through the air between conductors or between a conductor and earth.
The resulting electrical arc can reach temperatures exceeding several thousand degrees Celsius and generate intense thermal radiation. Depending on the available fault current and protective device operating time, personnel in close proximity may be exposed to:
- Severe burns
- Molten metal projections
- Blast pressure waves
- Hearing damage
- Flying debris
- Ignition of clothing and combustible materials
The severity of an arc flash event is typically expressed as incident energy, measured in calories per square centimetre (cal/cm²).
Incident energy represents the amount of thermal energy that may be received by a worker positioned at a specified working distance from the equipment.
The purpose of an arc flash study is to calculate this exposure and determine the controls necessary to reduce risk to an acceptable level.
What Is an Arc Flash Study?
An arc flash study is an engineering assessment used to evaluate the potential arc flash hazard throughout an electrical installation.
The study generally involves:
- Developing a power system model
- Calculating fault levels
- Assessing protective device operation
- Determining incident energy levels
- Calculating arc flash boundaries
- Assessing PPE requirements
- Conducting an arc flash risk assessment
- Producing equipment labels
The assessment is typically performed in accordance with recognised methodologies such as IEEE 1584, Electrical Arc Flash Hazard Management Guideline, NFPA 70E and relevant workplace electrical safety requirements.
The outcome is a detailed understanding of where hazards exist, how severe they may be, and what measures can be implemented to reduce exposure.
Why Arc Flash Labels Are Important
The most visible output of an arc flash study is the equipment label. These labels are generally installed on switchboards, motor control centres, distribution boards, substations, and other equipment where energised work or interaction may occur.
Depending on the methodology adopted by the site, labels may include:
- Incident energy levels
- Arc flash boundaries
- Working distances
- PPE requirements
- Equipment identification
The purpose of the label is to provide workers with immediate access to critical safety information before interacting with the equipment.
Importantly, the label should not be viewed as a substitute for a risk assessment. Arc flash labels should not be considered a replacement for a task-specific risk assessment. While the label provides critical information regarding incident energy exposure and PPE requirements, the risks associated with individual activities such as switching, testing, fault finding, maintenance, or operation of electrical equipment must also be assessed. Appropriate controls should be determined based on both the arc flash assessment and the specific work being performed.
The label communicates the results of the study but does not replace safe work procedures, isolation practices, permits, or task-specific risk assessments.
Arc Flash Studies for Existing Sites
Many existing industrial facilities were constructed before arc flash assessments became common practice. Even where studies have been performed previously, the results may no longer be valid.
Electrical systems rarely remain unchanged throughout their operating life. Typical modifications include:
- Additional transformers
- Network upgrades
- Generator installations
- Battery energy storage systems
- New switchboards
- Additional motors and loads
- Protection setting changes
Any modification that affects fault current levels or protection operation can significantly alter incident energy levels. As a result, arc flash studies should be reviewed whenever major changes occur within the electrical network.
In some cases, equipment that previously required relatively low levels of PPE may require substantially higher protection following system modifications. Conversely, upgrades to protection systems may reduce incident energy exposure and improve worker safety.
Arc Flash Studies for New Projects
Arc flash studies are equally important during the design and commissioning phases of new facilities. Performing the study before energisation allows hazards to be identified before personnel are exposed to risk.
This provides opportunities to optimise the design by:
- Selecting appropriate protection devices
- Reducing fault clearing times
- Improving discrimination
- Implementing arc energy reduction schemes
- Optimising equipment layouts
- Reducing operational risk
The study can also ensure arc flash labels are available from the commencement of operations, allowing maintenance personnel and operators to work with accurate safety information from day one. For major infrastructure projects, arc flash assessments are increasingly becoming a standard component of commissioning and handover documentation.
The Relationship Between Protection Systems and Arc Flash Energy
One of the most important concepts in arc flash analysis is that fault current alone does not determine hazard severity. Protective device operating time is often equally important.
A high fault current that is cleared rapidly may result in lower incident energy than a lower fault current that persists for a longer duration. For this reason, arc flash studies are closely linked with protection coordination studies.
Engineers frequently identify opportunities to reduce incident energy through:
- Protection setting optimisation
- Zone selective interlocking
- Differential protection schemes
- Maintenance switching modes
- Arc flash detection systems
In many cases, significant reductions in incident energy can be achieved without major equipment replacement.
Beyond PPE Selection
A common misconception is that the purpose of an arc flash study is simply to determine what PPE workers should wear. While PPE is an important control measure, it should not be considered the primary means of risk reduction, and the hierarchy of controls should always be considered.
Effective arc flash assessments often identify opportunities to:
- Eliminate energised work
- Improve isolation procedures
- Reduce incident energy levels
- Improve protection system performance
- Introduce remote operation capability
- Improve equipment condition monitoring
The objective is not simply to determine how much PPE is required, but to reduce the likelihood and consequences of an arc flash event wherever practical.
Maintaining Arc Flash Assessments
An arc flash study should be viewed as a living document rather than a one-off exercise. The assessment should be reviewed whenever significant changes occur within the electrical network.
Sites should also ensure:
- Single line diagrams remain current
- Protection settings are maintained
- Equipment labelling remains legible
- System modifications are documented
- Study assumptions remain valid
Without regular updates, labels may no longer accurately represent the actual hazard present within the electrical installation.
Closing Remarks
Arc flash studies provide far more than equipment labels. They form a critical component of electrical safety management by quantifying potential hazards, supporting risk assessments, and determining appropriate protective measures.
Whether for an existing facility or a new project, an arc flash assessment helps organisations understand the risks associated with their electrical infrastructure and provides the information necessary to protect personnel working on or near energised equipment.
When combined with accurate network models, current protection settings, and sound engineering practices, arc flash studies become a valuable tool for improving safety, supporting compliance, and reducing operational risk.
At Venn Power, we provide arc flash studies, protection assessments, and power system modelling services to help asset owners, operators, and project developers understand and manage electrical safety risks throughout the lifecycle of their facilities. To find out how we can support your next project, contact the Venn Power team today.
About the Author
Clement Venter is the Director of Venn Power and a Chartered Professional Engineer with over 20 years in the energy sector. He shares insights from his unique approach combining research, engineering, and design to drive smarter, more innovative energy solutions.