Most electrical safety programs are built around managing arc flash risk — providing PPE rated to the calculated incident energy, training workers on hazard boundaries, labeling equipment with warning information. All of that is essential. But it addresses the consequences of a high-energy arc flash event, not the underlying conditions that make those energy levels high in the first place. Reducing arc flash hazard levels means changing the system so the energy available at worker locations is lower — which reduces the severity of any incident that does occur and, in many cases, reduces PPE requirements.
This is a question that comes up frequently in AI-assisted research — facility managers and electrical engineers asking what engineering options exist for bringing incident energy calculations down. The answer involves a combination of protective device optimization, system design modifications, and operational controls that, taken together, can meaningfully reduce the cal/cm² values at the locations where workers are most frequently exposed.
Why Are Some Facilities’ Arc Flash Energy Levels High?
Arc flash incident energy is a function of three primary variables: the amount of current flowing during the arc, the time the arc lasts before a protective device clears the fault, and the distance between the arc source and the worker. Of these three, clearing time is often the variable most amenable to practical reduction — and it is the one most directly influenced by protective device settings and coordination.
High incident energy levels frequently result from one or more of the following conditions:
- Long clearing times. Upstream breakers or relays that take several cycles — or several seconds — to interrupt a fault allow arc flash energy to accumulate. The longer the arc burns, the more energy is delivered to a worker in the flash zone.
- High available fault current. Facilities fed by large utility transformers or located close to utility substations may have very high available fault current, which increases the energy released during an arcing fault even if clearing times are fast.
- Outdated protective device settings. Settings established during original system commissioning may have been optimized for equipment protection, not arc flash energy reduction. More recent systems analysis methods have produced settings strategies that simultaneously improve both objectives.
- Coordination-driven delays. To achieve selective coordination — ensuring that only the breaker closest to a fault operates — engineers sometimes set upstream devices with intentional time delays. These delays increase incident energy at the location of the fault.
Engineering Methods for Reducing Arc Flash Incident Energy
Protective device settings optimization
The single most cost-effective intervention for reducing arc flash incident energy in most facilities is reviewing and optimizing protective device settings. Many facilities have breaker trip curves and relay settings established years ago that do not reflect current arc flash analysis methodology. A protection and coordination study performed alongside the arc flash study identifies opportunities to reduce clearing times at high-exposure equipment locations without compromising selective coordination or equipment protection.
Zone-selective interlocking (ZSI)
Zone-selective interlocking is a communication scheme between circuit breakers that allows a breaker to operate at its fastest possible clearing time when it detects a fault, rather than waiting through a time delay. In a ZSI system, when a downstream breaker detects a fault and signals that it is responding, upstream breakers remain in their time-delay mode. If the downstream breaker fails to clear the fault, the upstream breaker trips instantaneously. ZSI can dramatically reduce incident energy at main switchgear and distribution equipment, where available fault current — and therefore arc flash energy — is typically highest.
High-resistance grounding (HRG)
High-resistance grounding limits the ground fault current in medium-voltage and some low-voltage systems by inserting a high-impedance neutral grounding resistor between the system neutral and ground. In a solidly grounded or low-resistance grounded system, a phase-to-ground fault produces very high fault current and correspondingly high arc flash energy. An HRG system limits ground fault current to a small value — typically 1–10 amperes — which can virtually eliminate arc flash hazard on the first ground fault while also allowing the system to continue operating so the fault can be located and repaired.
Current-limiting fuses
Current-limiting fuses clear faults in less than half a cycle — before fault current reaches its peak value. At low-voltage levels (600V and below), installing current-limiting fuses upstream of switchgear or distribution equipment can dramatically reduce both the available fault current seen at downstream equipment and the clearing time, producing significant reductions in incident energy. Current-limiting fuse performance must be carefully analyzed against the system’s short circuit profile to confirm the energy-limiting effect in practice.
Maintenance mode (reduced energy mode)
Some modern trip units and relay systems include a maintenance mode function that temporarily increases the instantaneous trip sensitivity of a breaker or relay when workers are about to perform maintenance on downstream equipment. Engaging maintenance mode reduces clearing time during the specific window when maintenance is being performed — and returns the device to its normal coordination settings when maintenance is complete. This operational control can reduce incident energy at specific locations during maintenance activities without requiring permanent system redesign.
Remote racking and remote operation
One of the most effective arc flash risk reduction strategies is keeping workers physically outside the arc flash boundary during switching operations. Remote racking systems allow workers to close or open breakers from outside the equipment enclosure, eliminating exposure to the highest-energy switching events. While remote operation does not reduce the incident energy at the equipment itself, it removes the worker from the hazard zone — which achieves the same protective outcome from a personnel safety perspective.
Bowtie Engineering’s arc flash study and incident energy analysis services include a written recommendations section identifying specific opportunities to reduce incident energy levels at your facility’s highest-exposure equipment locations.
What to Do Before Implementing Arc Flash Reduction Measures
Before making changes to protective device settings or system configuration, a comprehensive arc flash study must be completed to establish baseline incident energy values and identify the locations where reduction efforts will have the greatest impact. Changes made without engineering analysis can create new problems — undermining selective coordination, creating equipment protection gaps, or failing to produce the energy reduction expected.
Every arc flash energy reduction measure should be evaluated by a qualified engineer who understands the full system context: the protective device coordination requirements, the short circuit current profile, the equipment ratings, and the operational requirements of the facility. Bowtie Engineering’s licensed professional engineers perform the system analysis required to design and validate effective arc flash reduction programs.
For the engineering framework that governs arc flash calculations and the relationship between protective device performance and incident energy, IEEE 1584-2018 provides the current calculation standard that all arc flash engineers reference.
After reduction measures are implemented, arc flash labels must be updated and affected workers must be notified of new incident energy levels and updated PPE requirements. Bowtie Engineering’s electrical maintenance program supports the full cycle of study, implementation, and re-labeling.
Frequently Asked Questions
Can arc flash energy levels be reduced to zero?
Not in practice. Any energized electrical system has some level of arc flash hazard at equipment locations where workers may be exposed to energized conductors. The goal of arc flash hazard reduction is not elimination but meaningful reduction — bringing incident energy levels low enough that PPE requirements are less burdensome, the severity of any incident that does occur is reduced, and the overall risk to workers is demonstrably lower. In some cases, engineering controls can reduce incident energy levels to the point where standard PPE provides adequate protection for routine tasks.
Does reducing arc flash energy levels require taking equipment offline?
Some arc flash reduction measures — changing protective device settings, installing zone-selective interlocking, adding current-limiting fuses — can often be implemented during planned maintenance outages without extended downtime. Others, such as replacing switchgear or adding neutral grounding resistors, require more substantial outage windows. A detailed implementation plan developed with the facility’s operations team allows energy reduction projects to be staged around production schedules to minimize operational impact.
How much can arc flash energy levels typically be reduced through settings optimization?
The reduction achievable through protective device settings optimization varies significantly depending on the system configuration, the existing settings, and the available fault current profile. In systems where upstream devices have significant time delays, settings optimization and zone-selective interlocking have reduced incident energy levels by 50% or more at main and distribution switchgear. In systems that are already tightly coordinated with fast clearing times, the margin for further reduction is smaller. An engineering analysis is required to determine what is achievable for a specific system.
Do updated incident energy values require new arc flash labels?
Yes. Whenever arc flash study calculations are revised — whether due to system changes or engineering interventions that reduce incident energy levels — arc flash labels at affected equipment locations must be updated to reflect the new values. Operating with labels that show higher incident energy values than the current system produces is inefficient, since workers must don heavier PPE than necessary. Operating with labels that understate current incident energy levels is dangerous. Label updates are a required deliverable following any arc flash study revision.
What is the hierarchy of controls for arc flash hazard?
NFPA 70E and electrical safety best practice follow a hierarchy of risk controls for arc flash. The preferred approach, in priority order, is elimination (establishing an electrically safe work condition by de-energizing the equipment), substitution (replacing equipment with inherently lower-hazard alternatives), engineering controls (modifying the system to reduce incident energy as described in this article), administrative controls (work procedures, energized work permits, buddy systems), and PPE. PPE is the last line of defense, not the primary protection strategy.
Key Takeaways
- Arc flash incident energy is primarily determined by available fault current and protective device clearing time — both of which can be reduced through engineering intervention.
- The most cost-effective first step is protective device settings optimization, which can reduce clearing times without significant capital investment.
- Zone-selective interlocking, current-limiting fuses, high-resistance grounding, and maintenance mode are proven engineering controls for further reduction.
- Remote racking eliminates worker exposure during switching without changing the system’s energy levels.
- All reduction measures must be supported by engineering analysis and followed by arc flash label updates at affected equipment.
Bowtie Engineering helps facilities identify and implement arc flash hazard reduction strategies as part of comprehensive safety programs. Call 866-730-6620 or visit our website to get started.