Written by Don Freeston, Electrical Department Director
What Is An Arc Flash?
The Standard for Electrical Safety in the Workplace by the National Fire Protection Association (NFPA 70E) defines an arc flash as a “dangerous condition associated with the release of energy caused by an electric arc”. It is a flash of hot gas and metal vapor, which occurs when electric current leaves its intended path and travels through air between conductors or to the ground. It produces intense heat, blinding light, and a violent pressure wave, making it one of the most dangerous events in electrical systems
What Actually Happens during an Arc Flash?
Even a small arc flash can cause severe burns, hearing damage, or death.
When an electrical fault occurs, the air becomes ionized and turns into plasma, which allows electricity to travel through it. This triggers a rapid and destructive chain reaction:
Temperatures up to ~35,000°F (19,400°C) — hotter than the surface of the sun.
Blinding light and ultraviolet radiation.
Molten metal ejected at high speed.
A pressure wave (arc blast) strong enough to throw a person across a room.
What causes an arc Flash?
Accidental contact with energized parts by personnel or rodents
Dust, corrosion, or moisture creating unintended conductive paths
Loose or degraded connections
Dropped tools inside energized equipment
Faulty or poorly maintained electrical components
Incorrect installation or unsafe work practices
Why Arc Flash Analysis is EssentiaL (click to read more)
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An arc flash can release:
Temperatures hotter than the surface of the sun
Shockwaves strong enough to throw a person across a room
Blinding light and molten metal
Even a small electrical fault can escalate into something life‑altering. Analysis helps prevent that.
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OSHA 29 CFR 1910.132 (d) – Requires employers to assess the workplace to determine hazards and select appropriate personal protective equipment (PPE). OSHA requires employers to identify electrical hazards, warn employees using signs/labels, and provide PPE and training.
NEC 110.16 – Requires that switchboards, panel boards, industrial control panels, and motor control centers requiring maintenance, inspection, servicing, etc., be field marked to warn qualified persons of potential electric Arc Flash Hazards.
NFPA 70E – Requires that an Arc Flash Analysis be performed to properly identify hazards and protect operations personnel from injury due to an arc flash event. This study shall determine the arc flash hazard boundary and the PPE required to protect qualified persons while working within this boundary.
IEEE 1584 – This guide to performing arc flash hazard calculations includes the detailed steps on how to perform this analysis and all required steps that should be followed.
NFPE 70E makes it clear that the facility owners are responsible for installing and maintaining arc flash labels. Arc flash labels are required on any equipment likely to require examination, adjustment, servicing, or maintenance while energized, including equipment at 50 volts or more.
This includes:
Switchboards
Panelboards
Switchgear
Industrial control panels
Motor control centers
Transformers
Disconnect switches
Meter socket enclosures
Therefore, arc flash labels are required to be installed at all industrial, commercial, and institutional workplaces.
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Not all electrical work requires the same level of protection. Arc flash analysis calculates:
Incident energy levels
Arc flash boundaries
Required PPE category
This ensures workers aren’t under‑protected or over‑protected (which can also be unsafe).
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Arc flash studies often uncover:
Improper breaker settings
Coordination issues
Undersized equipment
Aging or unsafe components
Fixing these reduces downtime and prevents equipment damage.
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An arc flash incident can lead to:
Fatalities
Medical costs
Lawsuits
OSHA fines
Equipment replacement
Production loss
A proper analysis is far cheaper than the consequences of not having one.
How Terra Conducts Arc Flash Analysis
Our electrical team will deliver a comprehensive Arc Flash Analysis that ensures full compliance with NFPA 70E, IEEE 1584, NEC 110.16, and OSHA 29 CFR 1910.132(d).
1. Project Initiation
Upon contract execution, TERRA:
Hosts a virtual kickoff meeting
Defines scope, schedule, budget, and communication protocols
Establishes a secure file‑sharing portal
Requests utility data and existing electrical documentation
2. Field Data Collection and System Verification
Request the following data from the utility company for each location: Transformer manufacturer, primary/secondary voltages, KVA rating, winding configuration, impedance over resistance ration, and fault impedance value.
Conduct on-site walkthroughs of each facility, accompanied by electricians or maintenance personnel who are qualified to safely open panel covers.
Collect detailed nameplate data on all electrical components including switchgear, panelboards, MCCs, transformers, feeders, and protective devices. In addition, TERRA will document lengths for feeders and branch circuits, wire type, and overcurrent protective device makes/models/settings.
Develop and field-verify single-line diagrams for each building to ensure modeling accuracy.
3. Electrical System Modeling and Analysis
Build a digital model of each facility’s power distribution system using industry-standard software (e.g., SKM PowerTools or EasyPower).
Perform:
Short Circuit Current Study (SCSS) to evaluate fault current levels and verify equipment ratings. This analysis will allow us to confirm that switchgear, transformers, and other components can withstand mechanical and thermal stresses during faults.
Overcurrent Protective Device Coordination Study to optimize settings for selective coordination and minimize incident energy, by isolating faults without affecting upstream system. Emergency systems will be reviewed per NEC 620.62, 700.27, and 701.18.
Arc Flash Hazard Analysis using IEEE 1584 and NFPA 70E methodologies to calculate incident energy, flash boundaries, and PPE requirements.
4. Labeling and Safety Signage
Generate ANSI Z535.4-compliant vinyl arc flash warning labels for each applicable equipment section.
Label content will include voltage, incident energy, PPE class, fault current, approach boundaries, and equipment identifiers.
Labels will be installed only after overcurrent device settings are adjusted to match the study recommendations.
5. Electrical Safety Training
Deliver a 4-hour NFPA 70E training session for personnel, covering:
Arc flash hazard awareness
PPE selection and use
Safe work practices and approach boundaries
Label interpretation and emergency response
6. Final Report and Recommendations
Provide a detailed report in both digital and hard copy formats, including:
Verified one-line diagrams
Fault and coordination input data
Time-current curves and arc flash evaluation tables
Mitigation strategies for equipment with incident energy ≥ 4 cal/cm²
Recommended fuse replacements and breaker setting adjustments to reduce PPE class
7. Quality Assurance and Compliance
All work undergoes internal QA/QC and review by a licensed Professional Engineer.
The final report will meet or exceed all applicable codes and standards, ensuring the owner’s compliance and personnel safety.