What Happens During an Arc Flash Study?

Before the Study: What to Prepare

The single most impactful thing a facility can do before an arc flash study begins is gather existing electrical documentation. The more complete this documentation, the faster and less expensive the study will be — and the higher-quality the final deliverables.

Gather Existing Documentation

Locate and consolidate the following before engaging a provider:

• Single-line diagrams (SLDs) — even outdated SLDs are better than none; they give the provider a starting framework
• Panel schedules — the load schedule for each distribution panel
• Transformer nameplates or data sheets — manufacturer, kVA rating, primary and secondary voltages, impedance percentage (%Z); this data is critical for fault current calculations
• Motor control centre schedules — breaker ratings, overload settings, motor horsepower for each starter
• Protective relay settings documentation — time-current curves, relay setting sheets, protection relay model numbers
• Utility fault current data — the available fault current at your point of connection with your electricity distributor; most Ontario LDCs will provide this in writing on request

Identify Internal Contacts

Designate who will accompany the provider's engineers during the site visit. An experienced internal electrician who knows the facility's electrical layout, where panels are located, which rooms require special access, and where protection settings are documented saves significant field time. Their knowledge of undocumented system changes since the last study is also invaluable.

Plan for Electrical Room Access

Every electrical room, mechanical room, and equipment pad in scope needs to be accessible during the site visit. Arrange for keys, access codes, and any permits (confined space, hot work) that may be required for specific areas. Production does not need to stop — but locked rooms that the provider cannot enter mean missing data and a return visit.

Phase 1: Scoping and Documentation Review

The engagement begins with a scoping call or meeting — typically remote — during which the provider establishes the study boundaries. Scoping questions cover:

• Which buildings, voltage levels, and equipment types are in scope
• Approximate node count (which drives the quote)
• Whether existing single-line diagrams are available, and their approximate accuracy
• Utility fault current data availability
• Whether this is a new study or a five-year update — and if an update, whether the existing power system model is accessible
• Any specific concerns: high-energy locations workers are already aware of, equipment of unknown rating, recent system changes

Following scoping, the provider reviews any existing documentation you provide — SLDs, panel schedules, relay setting documents — to identify gaps that will need to be filled during the site visit and to begin preliminary system modeling.

Phase 2: The Site Visit

The site visit is the phase most facility managers have the most questions about. Here is what the provider's engineers are actually doing when they arrive at your facility.

Systematic Equipment Survey

Engineers work through the facility room by room, systematically visiting every electrical panel, MCC, switchgear lineup, and transformer in scope. At each location, they collect:

• Equipment nameplate data — manufacturer, rating, voltage, interrupting capacity
• Protective device data — breaker model, frame size, trip rating; fuse type and ampere rating; relay model and current transformer ratios
• Protection settings — instantaneous pickup, time-delay settings, long-time and short-time characteristics
• Physical connections — verifying what feeds each piece of equipment and what it feeds, confirming or correcting the single-line diagram

Panels are opened — but not worked on while energized during data collection. Engineers use appropriate PPE for the exposure involved in opening and inspecting energized panel covers. Production equipment continues to run.

Transformer and Medium-Voltage Equipment

Transformer nameplates are photographed or recorded in full. For medium-voltage equipment (above 600V), access arrangements may require coordination with operations staff and may be deferred to a scheduled maintenance window where safe access requires equipment to be de-energized. Most low-voltage equipment data collection can proceed during normal operations.

Duration

Field data collection takes one to two days for most mid-size Ontario manufacturing and industrial facilities (20–60 nodes). Large multi-building sites with 100+ nodes typically require three to five days of field time spread across one or more visits. Facilities without existing SLDs — where engineers must document the system from scratch — require significantly longer site visits.

For example, the tier-one automotive supplier facilities and distribution centres common in Brantford's industrial base typically scope at two to three days of field work, while large institutional campuses — the kind found in research university and hospital complexes — can require five or more days to fully document all electrical rooms across multiple buildings.

Phase 3: Engineering Analysis

After the site visit, the engineering analysis is performed off-site. This phase has no direct facility involvement — it is the computational and documentation work done by the provider's engineers.

Power System Model Development

All field data is entered into the power system analysis software (ETAP, SKM Power Tools, or equivalent) to build a complete model of your electrical distribution system. For a new study, this means building the model from scratch — entering every bus, transformer, cable, and protective device, setting parameters, and verifying that the model is internally consistent. For a five-year update, the existing model is updated with changes identified in the site visit.

Model development is typically the most time-consuming phase of the study for new engagements. A 50-node system model takes approximately two to four weeks of engineering time to build, verify, and validate.

Short Circuit Analysis

The software calculates the maximum available fault current at every bus in the system. This analysis also verifies that your protective devices are rated for the fault currents they may be required to interrupt — an important safety check that is independent of, but feeds into, the arc flash calculations.

Protective Device Coordination Study

The coordination study verifies that breakers, fuses, and relays operate in the correct sequence during faults — downstream devices before upstream devices. Miscoordination is common in facilities that have grown over time through incremental expansions without system-level electrical review. The analysis produces time-current coordination curves showing the operating characteristics of each protective device and identifying any coordination gaps. Where miscoordination exists, the coordination study recommends setting changes that would restore proper coordination — and often simultaneously reduce arc flash incident energy levels by reducing clearing times.

Incident Energy Calculations (IEEE 1584-2018)

With the model complete and protection settings verified, the engineer runs arc flash calculations at every node using the IEEE 1584-2018 methodology. The calculation produces, at each location: the incident energy (cal/cm²), the arc flash boundary, the required PPE category, and the working distance used in the calculation. These values are what appear on the arc flash warning labels.

Phase 4: Report Delivery and Walkthrough

The final deliverable is a PE-stamped engineering report containing the complete study findings, along with the updated single-line diagram, arc flash label schedule, and PPE recommendations. A qualified provider delivers the report with a walkthrough meeting where they:

• Review the methodology and key findings
• Highlight locations with the highest incident energy — the Category 3 and 4 locations that deserve special attention in your PPE program and energized work procedures
• Explain any coordination findings and the recommended setting changes
• Walk through the arc flash label schedule to confirm your team understands what labels apply where
• Answer questions about implementation — label installation, PPE procurement, qualified person training implications

After the Study: What to Do With the Results

Receiving the report is the beginning, not the end. The study creates compliance obligations that must be acted on:

1. Install arc flash labels — labels must be physically installed at every panel and piece of equipment before energized work resumes. If label printing and installation are not included in your study scope, arrange this separately; physical installation typically takes one to two days for a mid-size facility.
2. Procure appropriate PPE — ensure workers have access to the PPE required for each category of location they work at. A facility with Category 3 locations that only has Category 1 PPE in stock is not compliant even with a current study.
3. Update your energized work permit process — incorporate the study's incident energy values and PPE requirements into your permit templates.
4. Train qualified persons — workers who perform energized electrical work should be briefed on the study findings, particularly the high-energy locations applicable to their tasks.
5. Implement coordination setting changes — if the coordination study identified setting changes that would reduce incident energy levels, prioritize those changes; they have direct safety benefits and reduce PPE requirements at affected locations.
6. Record the completion date and set your update reminder — the five-year clock starts now. Set a calendar reminder for four years out to begin planning the update.

Typical Timeline: Engagement to Labels Installed

Timeline assumes current single-line diagrams available. Add 2–4 weeks for facilities without SLDs. Five-year updates are typically 30–40% faster than new studies at equivalent scope.

Frequently Asked Questions

How long does an arc flash study take?

Most Ontario industrial facilities can expect 4 to 12 weeks from initial engagement to final report. Simple facilities with fewer than 20 panels and good documentation sometimes complete in 3–4 weeks. Complex multi-building sites with 150+ nodes and no existing single-line diagrams can take 10–16 weeks. Five-year updates are typically 30–40% faster than new studies at equivalent scope.

What does my facility need to provide for an arc flash study?

Ideally: current single-line diagrams, panel schedules, transformer nameplate data, motor control centre schedules, protective relay setting documents, and utility fault current data from your electricity distributor. The more complete this documentation, the faster and less expensive the study. A provider will work without any of this, but field data collection will take longer and cost more.

Do workers need to leave during the arc flash study site visit?

No. Arc flash study site visits are performed during normal facility operations in the large majority of cases. Electrical rooms need to be accessible and panels opened for data collection, but production does not need to stop. Medium-voltage equipment that can only be safely accessed during outages may require a scheduled maintenance window for data collection.

Who from my facility needs to be involved in the arc flash study?

The primary contacts are the EHS manager or safety coordinator, the facility electrical maintenance lead or chief electrician, and the plant or facilities manager. An experienced internal electrician who can accompany the provider's engineers during the site visit significantly improves field data collection efficiency and the accuracy of the resulting model.