| Quick Answer: A short circuit study calculates how much fault current can flow at each point in the system. A coordination study tunes protective devices so the closest one trips first, isolating faults with minimal disruption. An arc flash study uses both results to calculate incident energy and produce hazard labels. They are sequential — the short circuit study feeds the coordination study, and both feed the arc flash study. |
Facilities often hear these three terms used loosely, as if they were the same project under different names. They are not. Each study answers a different question, and they build on one another in a specific order. Understanding the sequence helps facility managers scope the work correctly and avoid paying for a re-do.
At a Glance: Three Studies, Three Jobs
| Study | Core question | Main deliverable |
|---|---|---|
| Short circuit study | How much fault current is available here? | Fault current values at each bus; equipment rating check |
| Coordination study | Which device should trip first, and when? | Protective device settings and time-current curves |
| Arc flash study | How much incident energy and what PPE? | Incident energy values, boundaries, and warning labels |
The Short Circuit Study: How Much Fault Current?
The short circuit study, sometimes called a fault current study, calculates the maximum current that could flow if a fault occurred at each point in the electrical system. This matters for two reasons. First, every breaker and piece of switchgear has an interrupting or withstand rating; if available fault current exceeds that rating, the equipment can fail catastrophically during a fault. The study flags any under-rated equipment. Second, the fault current values are a required input to everything that follows. You cannot coordinate protective devices or calculate arc flash energy without knowing the fault current first.
The Coordination Study: Which Device Trips First?
The protective device coordination study uses the fault current data to set up the system’s protective devices so they operate selectively. The goal is that the device closest to a fault trips first, isolating only the affected portion of the system while everything upstream stays energized. Done well, a fault in one machine takes down that machine — not the whole plant. The deliverable is a set of device settings and time-current curves showing how breakers and relays are tuned to coordinate. Poor coordination is both a reliability problem and a safety problem, because mis-set devices can clear slowly and raise arc flash energy.
The Arc Flash Study: How Dangerous Is It to Workers?
The arc flash study, or incident energy analysis, is the safety payoff of the first two. Using the fault currents from the short circuit study and the clearing times from the coordination study, it calculates the incident energy and arc flash boundary at each location, typically with IEEE 1584. The output is the set of equipment labels that tell workers the incident energy, the boundary distance, and the PPE required. This is the study that directly protects the people who open the gear, and it is the core of Bowtie’s incident energy study service.
Why the Order Matters
The dependency is strict. The arc flash result is only as good as the coordination data, and the coordination work is only as good as the short circuit data. If a facility commissions an arc flash study without valid short circuit and coordination inputs, the labels can be wrong. This is also why changing protective device settings later can invalidate existing arc flash labels — the energy calculation assumed specific clearing times. Treating the three as one connected effort, rather than separate purchases, produces accurate and durable results.
How the Studies Connect to Maintenance
Even a perfect set of studies degrades if the equipment is not maintained. Protective devices that drift out of calibration clear faults more slowly than the coordination study assumed, quietly raising real incident energy above what the labels show. That is why these studies pair naturally with a testing program; coupling them with ongoing electrical maintenance and NETA testing keeps the calculated values true to the system over time.
When Does a Facility Need These Studies?
Several triggers point to commissioning or refreshing the full set. A new facility or a significant electrical expansion needs all three before energizing, because the equipment ratings, coordination, and arc flash labels all have to be established from scratch. An existing facility that has never had an arc flash study needs one to meet NFPA 70E and to put accurate labels on its gear. Major changes — a new utility service or transformer, added large loads, or replaced switchgear — alter fault currents and clearing times, which can ripple through all three studies. Even insurers and corporate safety programs increasingly require current studies as a condition of coverage or internal audit.
How Often Should the Studies Be Reviewed?
NFPA 70E calls for the arc flash study to be reviewed periodically and whenever a major modification could affect the results, with a common practice being a review at least every five years. But the calendar is only half the trigger; any significant change to the electrical system should prompt a re-evaluation regardless of how recently the study was done. Because the three studies are linked, a change that alters fault current or protective device settings can invalidate the arc flash labels even mid-cycle. Keeping the one-line diagram current and feeding maintenance findings back into the model is what keeps the studies — and the labels workers rely on — trustworthy between formal reviews.
For facilities scoping this work, the most cost-effective path is almost always to commission the three studies together as a single coordinated engagement. Bundling them avoids paying an engineer to collect the same field data and build the same system model three separate times, and it guarantees the inputs flow cleanly from one study to the next. It also produces a single, consistent set of deliverables — an updated one-line diagram, fault current values, coordinated device settings, and arc flash labels — that all reference the same model of the system. When these are done piecemeal by different parties at different times, the assumptions rarely line up, and the facility can end up with labels that quietly contradict the protection settings actually in the field.
Frequently Asked Questions
Are these three studies the same thing?
No. Each answers a different question, though they are closely related and usually performed together.
Which study comes first?
The short circuit study, because its fault current data feeds both the coordination and arc flash studies.
Can I get an arc flash study by itself?
Only meaningfully if valid short circuit and coordination data already exist; otherwise the labels may be inaccurate.
What does each study deliver?
Fault currents (short circuit), device settings and curves (coordination), and incident energy plus labels (arc flash).
Why do device changes affect arc flash labels?
Arc flash energy depends on protective device clearing times, so changing settings changes the calculated energy.
Key Takeaways
- Short circuit, coordination, and arc flash studies answer three different questions.
- They are sequential: short circuit data feeds coordination, and both feed the arc flash study.
- An arc flash study without valid inputs can produce inaccurate labels.
- Maintenance keeps protective device behavior — and the study results — accurate over time.