In the last decade, commercial and utility solar sites have changed more than their rooftop arrays and mounting hardware. System voltages have risen. Inverters and combiner boxes have become denser. Battery storage is increasingly common. These changes have improved generation and lowered levelized costs. They have also shifted the operational risk profile in ways that few organizations fully account for.
Arc flash incidents remain a clear and present danger in this environment. When an arc occurs, the result is a rapid release of energy that can destroy equipment and seriously injure anyone nearby. For operators and asset managers, the question is practical: how do you convert technical exposure into manageable, auditable steps? The answer begins with a comprehensive arc flash study that addresses both alternating current and direct current systems and that ties recommendations to operations and finance.
This article provides a practical, authoritative guide for decision-makers. It explains how arc flash behavior differs across AC and DC systems, outlines the engineering elements of a modern study, describes where dollars and time are saved, and shows how to embed findings into maintenance and procurement practices. It also explains why the study matters most in solar and BESS sites and how to prioritize mitigations for the greatest operational impact.
Three developments change the arc flash calculus for solar and storage portfolios.
First, nominal DC voltages at commercial sites have increased. Many new systems now use 1500 volt architectures. Higher voltage changes how faults initiate and propagate in DC circuits. Unlike AC arcs, which cross zero voltage regularly and can extinguish themselves, DC arcs can sustain if the fault path remains conductive.
Second, equipment has become more compact. Manufacturers optimize for cost and installation footprint. That leads to tighter conductor spacing and smaller enclosures. A fault in a dense assembly will contain higher temperatures and pressure, and that often increases material damage and the risk to personnel.
Third, storage systems introduce new fault currents and pathways. Batteries can supply fault current that behaves differently from the grid. When inverters and batteries interact, protective device coordination becomes more complex. Without clear modeling of both sources, incident energy predictions will be incomplete and mitigation efforts may miss the highest-risk scenarios.
Taken together, these factors make arc flash studies indispensable for modern solar operations. They are not a regulatory checkbox. They are a map. The map shows where people work, where incident energy is unacceptable, and which engineering changes reduce exposure without unnecessary capital expense.
Operators increasingly call on Illumine-i to translate complex AC/DC interactions into clear operational steps.
Engineering decisions in a solar portfolio are close cousins to financial ones. Replacing a damaged switchboard, combiner box, or inverter can cost tens of thousands of dollars. Extended outages reduce revenue under power purchase agreements and can lead to contractual penalties. OSHA penalties for serious violations now exceed six figures per citation. Insurance underwriting also responds to documented operational discipline.
An arc flash study has a clear return on investment when framed against these outcomes. The study identifies targeted mitigations that prevent the worst losses. In many facilities the cheapest and most effective measures are not new hardware. They are changes to protection settings, improved coordination, or modest layout changes. Those adjustments can reduce incident energy and reduce the classification of work tasks so technicians spend less time in high-level PPE and more time performing productive maintenance.
A precise study also reduces uncertainty during audits and inspections. Documentation that ties calculations to field-verified conditions shortens audit time and strengthens insurance conversations. In short, the study turns technical risk into financial clarity.
A modern, useful study covers more than a set of calculations. It follows a clear sequence of field verification, modeling, analysis, and prioritization. At minimum it should include the following elements.
Field data capture
Field verification is essential. Many models fail because the assumed wiring or protective device is not what exists in the field. A study team will verify single-line diagrams, confirm actual device make and model, collect nameplate data, and note any deviations from as-built drawings. Thermal imaging and visual inspection of enclosures often reveal maintenance issues that affect fault initiation.
Illumine-i’s field teams verify nameplate data and thermal baselines before any model runs, because assumptions on paper rarely match the field.
Fault current modeling
For AC systems, the study models available bolted fault currents at relevant buses. For DC and hybrid sites, the study models fault contributions from PV arrays, inverters, and battery systems. The model must reflect seasonal and configuration variations. For example, a BESS system operating in charge mode behaves differently from the same system in discharge mode. A single, static current assumption will not suffice.
Protective device timing and coordination
Clearing time is the single most important variable in incident energy. The faster a device clears a fault, the less energy is released. The study reviews device characteristics and settings, examines selective coordination between upstream and downstream devices, and models how device interactions affect clearing. Where coordination is imperfect, the study identifies adjustments that reduce incident energy while preserving system selectivity.
Incident energy calculation and working distances
Using accepted methods, the study calculates incident energy at defined working distances. For AC systems IEEE 1584 models remain the standard for many applications. For DC systems and PV arrays, the calculation methods must reflect DC arc physics. The study should produce incident energy contours and recommended PPE categories for each point of access.
Enclosure and geometry effects
Compact enclosures amplify arc effects. The study documents enclosure types and sizes and captures how enclosure geometry changes incident energy and pressure wave effects. This step often changes mitigation priorities; an enclosed combiner box may be a higher priority than an open disconnector because the consequences within a sealed space are more severe.
Environmental and regional factors
Climate changes electrical behavior. Heat alters conductor resistance and can affect fuse clearing time. Humidity and salt increase tracking in outdoor enclosures. Freeze and thaw cycles permit condensation that creates hidden conductive paths. A complete study notes these drivers and recommends equipment choices and maintenance items that address them.
Mitigation recommendations and prioritization
A study ends with a pragmatic mitigation plan. That plan ranks actions by their risk reduction and cost. Typical mitigations include protection setting changes, installation of arc detection relays, relocation of conductors, enclosure upgrades, and procedural steps such as changes to work permits. Each recommendation should include an estimated cost and an expected reduction in incident energy or legal exposure.
Arc flash analysis and work practices are governed by NFPA 70E and related OSHA clauses. NFPA 70E defines the requirements for electrical safety in the workplace, including labeling, PPE selection, and employer obligations for hazard analysis. IEEE 1584 (AC) and accepted DC modeling approaches inform calculations and incident-energy methods. A credible study ties IEEE/technical methods to NFPA 70E obligations and to the evidence auditors expect.
Understanding the differences between AC and DC fault behavior is crucial for accurate modeling.
AC faults have a voltage waveform that crosses zero several times per cycle. Those zero crossings can help extinguish arcs. DC faults do not have that natural extinguishing behavior. When a conductive path exists in a DC circuit, the arc may sustain until the source is isolated or until the arc itself modifies the path.
PV strings are particularly vulnerable to sustained arcs because they can provide current even under partial shading. When devices do not detect or clear these low-current arcs, the result can be a prolonged event that damages equipment and creates fire risk. In contrast, a typical AC system may detect a high fault quickly and operate protective devices in milliseconds.
Because of this distinction, a study for a solar site should model DC arc scenarios separately and ensure that protective devices and fusing strategies address sustained low-current arcs. Where BESS is present, the study should model how battery currents interact with PV and grid contributions.
Not all recommendations carry equal cost or complexity. Some deliver large reductions in incident energy for modest investment. Typical levers include these.
Protection setting optimization
Adjusting trip curves and coordination reduces clearing times. This often requires only reprogramming devices and retesting coordination. The operational impact is low and the risk reduction can be substantial. In multi-site portfolios Illumine-i often finds that coordinated setting changes deliver the largest risk reduction per dollar.
Arc detection and trip devices
Arc detection relays sense the light or pressure signature of an arc and command fast isolation. They add cost, but in high-risk enclosures they can be decisive in reducing incident energy.
Enclosure redesign and separation
Increasing conductor spacing or redesigning combiner boxes can reduce the likelihood of sustained arcs. These measures require construction but change the fundamental physics that permit an arc to sustain.
Maintenance practice changes
Improved torque protocols, thermal imaging, and scheduled inspections reduce the likelihood of initiating faults. These practices are inexpensive and multiply the effectiveness of hardware interventions.
Operational modes and work permits
Temporary maintenance settings, lockout protocols, and clear energized-work permits limit exposure during tasks. A repeatable work package protects personnel and documents due diligence.
Each site will need a different mix. The role of the study is to show which mix yields the highest risk reduction per dollar and per hour of maintenance time.
A strong O&M contract ties study deliverables to ongoing work. That reduces ambiguity during inspections and audits. Typical contract elements that protect owners include:
• A qualified-person requirement for electrical work.
• Guaranteed periodic updates to arc flash calculations.
• DC-specific modeling in addition to AC analysis.
• Thermographic baseline surveys and periodic IR scanning.
• Change-control procedures for short-circuit and coordination settings when utilities modify fault contribution.
• A clear energized-work permit process and documentation retention.
Insurers and auditors look for documented, repeatable process. A study that is field verified, labeled, and tied to a maintenance plan demonstrates operational control. That improves negotiation leverage in underwriting and shortens audit cycles in regulatory reviews.
To make recommendations concrete, consider five common scenarios and the priorities each brings.
Rooftop commercial C&I
Rooftop arrays are often smaller in scale but densely packed. The highest risks are combiner boxes and inverters. Quick wins typically include thermal imaging programs and fuse coordination reviews.
Ground-mount utility arrays
Large sites introduce long DC cable runs and central inverters. The study must model cable impedance and centralized enclosure behavior. In these sites, faster upstream clearing and strategic arc detection often yield the greatest benefit.
BESS-integrated sites
Battery systems change fault contributions and timing. Modeling must include charge and discharge states. Battery protection and inverter coordination are central to reducing incident energy.
Warehouse and cold-climate sites
Freeze–thaw cycles create moisture intrusion that increases tracking risk. Condensation heaters and drainage in enclosures become important mitigations.
Desert and high-temperature sites
High ambient temperatures affect fuse behavior and conductor resistance. Heat-tolerant components and summer worst-case modeling are recommended.
Each scenario requires different focus. The study should align with the site’s operational patterns and climatic realities.
Cost depends on scale. For a small rooftop commercial system with limited equipment, a study that covers AC service and major combiner boxes may be completed for a modest fee. For larger utility or hybrid sites with extensive DC modeling and BESS integration, costs reflect greater modeling complexity and field effort.
A typical timeline ranges from several days of site data capture for small sites to multiple weeks for larger portfolios. The most expensive part of the process is accurate field verification. Time spent there reduces uncertainty and prevents rework.
When budgeting, focus on expected outcomes. Benchmark estimated mitigation costs against avoided replacement costs, projected downtime, and regulatory exposure. Many operators find that targeted mitigations identified in an arc flash study pay for themselves the first time a major incident is avoided.
Industry practice is to review arc flash studies at least every five years or whenever a major electrical change occurs. Changes that trigger an immediate review include adding BESS, changing inverter configuration, replacing major switchgear, or when utility fault contributions change significantly.
More frequent reviews may be warranted in sites with aggressive maintenance cycles, high environmental stress, or after any event that suggests protection did not operate as intended.
A study that sits on a shared drive is ineffective. The value comes when findings are embedded into work instructions, permit-to-work documentation, and procurement specifications. Practical steps include:
• Labeling equipment with calculated incident energy and working distances.
• Updating maintenance task lists to reflect revised PPE requirements.
• Including protection setting requirements in procurement language for replacement devices.
• Training technicians on new boundaries and procedures.
• Maintaining a living record of any field changes that affect calculations.
When these steps are taken, maintenance becomes measured and repeatable. That improves safety, reduces downtime, and makes audits routine rather than disruptive.
Arc flash studies are technical work. They are also a means of operational control. Organizations that take them seriously gain confidence that personnel will be protected, assets will be preserved, and operational decisions will be made on evidence.
Illumine-i works with operators to translate study results into operational programs. That includes field-verified modeling, prioritized mitigation plans, and practical steps for embedding findings into O&M practices. In multi-site portfolios, consistent modeling and contract language reduce ambiguity across vendors and locations.
If your portfolio has not been reviewed recently, begin with the one-line diagram. Often this simple document, when modeled with current field data, reveals priorities that pay back quickly in risk reduction and operational clarity.
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