When Ontario facility managers request an arc flash study, they often receive proposals with varying scope descriptions. Some proposals reference “arc flash hazard analysis.” Others reference “power system study.” Still others include “short circuit analysis” and “protective device coordination study” as separate line items — sometimes included, sometimes quoted as add-ons. Understanding what each of these analyses actually does clarifies why a complete engagement includes all three, and why receiving only the arc flash calculations alone is an incomplete service.
The Three Integrated Analyses
A complete power system study for arc flash compliance consists of three integrated engineering analyses:
- Short circuit analysis — calculates the maximum available fault current at every bus in the system
- Protective device coordination study — verifies that breakers, fuses, and relays operate in the correct sequence during faults
- Incident energy analysis (IEEE 1584-2018) — calculates the arc flash energy at every work location using the results of analyses 1 and 2
These are not independent deliverables. The short circuit analysis feeds directly into the arc flash calculations. The coordination study determines arc flash clearing times, which are the primary driver of incident energy values. A provider who offers “arc flash calculations” without the coordination study has provided an analysis whose critical input — clearing time — was either assumed, simplified, or based on nominal device ratings rather than the actual protection settings at your facility.
What a Short Circuit Analysis Does
A short circuit analysis calculates the maximum fault current available at every bus in your electrical distribution system — from the utility service entrance through every transformer, switchgear section, and distribution panel. This analysis serves two purposes:
Equipment rating verification. Short circuit analysis verifies that your installed electrical equipment is rated to withstand and interrupt the fault currents it may encounter. Circuit breakers, fuses, and disconnect switches have maximum interrupting ratings — if the available fault current at a location exceeds the device’s interrupting rating, the device may not be able to clear the fault safely. This is a critical safety issue independent of arc flash — an under-rated breaker that fails to clear a fault creates a prolonged fault condition that dramatically increases incident energy and can cause catastrophic equipment damage.
Input to arc flash calculations. The fault current values calculated in the short circuit analysis feed directly into the IEEE 1584-2018 arc flash calculations. The higher the available fault current, the higher the potential incident energy at that bus location — all other factors being equal.
What a Protective Device Coordination Study Does
The coordination study verifies that your protective devices — circuit breakers, fuses, and protective relays — are set to operate in the correct sequence during a fault. “Correct sequence” means downstream devices (closer to the fault) should operate before upstream devices, clearing the fault at the minimum possible scope and minimizing the outage area.
For arc flash purposes, coordination is important because protective device clearing time is the primary determinant of how long an arc flash event lasts — and therefore how much incident energy it produces. The IEEE 1584-2018 calculation produces higher incident energy values for longer clearing times and lower values for shorter clearing times.
A coordination study identifies two types of problems:
Miscoordination (too slow). An upstream device that trips before the downstream device intended to clear the fault results in a larger-than-necessary outage scope. From an arc flash perspective, if the upstream device has a time-delay setting that is inappropriate for the fault level, it may also contribute to longer clearing times at the downstream bus — increasing incident energy at that location.
Instantaneous trip settings (too fast — in a different way). Upstream breakers with instantaneous pickup settings that overlap with downstream breakers can cause the upstream device to trip simultaneously, again producing unnecessary outage scope. Understanding the time-current characteristics of every device in the system, and verifying they coordinate correctly, requires analysis that the coordination study provides.
The practical payoff: In many Ontario manufacturing and industrial facilities, straightforward coordination improvements — adjusting relay settings, resizing fuses, or changing trip curve settings — reduce arc flash clearing times at multiple downstream locations. This reduction in clearing time directly reduces calculated incident energy. A Welland fabrication plant that implements a coordination study recommendation reducing an upstream breaker’s time-delay setting by 0.2 seconds might find that five MCC bus locations drop from Category 3 to Category 2 requirements — a significant simplification of the PPE program with direct worker safety benefits.
For Sault Ste. Marie’s primary metals and industrial facilities, where aging protection schemes installed over decades of plant expansion often have coordination gaps, the coordination study frequently uncovers settings that were appropriate for the original system configuration but are no longer correct given subsequent additions. The resulting setting corrections reduce incident energy while also improving fault clearing performance.
Why Some Proposals Omit the Coordination Study
The coordination study adds engineering time to the engagement — and therefore cost. A provider who omits it from the standard scope can submit a lower headline price while technically delivering “arc flash calculations.” The proposal may not explicitly state that the coordination study is excluded; it simply may not appear in the scope description.
The consequence: the provider performing the arc flash calculations must still make an assumption about arc flash clearing time at each location. Without a coordination study, this assumption typically relies on the nominal time-delay settings published in device manufacturer specifications — which may not match the actual as-found settings in your facility. In older Ontario industrial facilities where protection settings have been adjusted informally over years of plant modifications, the difference between nominal and actual settings can be significant.
The Combined Value
The practical reason to insist on all three analyses in a single engagement is the interaction between them:
- The short circuit analysis establishes the fault current at every bus
- The coordination study verifies the actual clearing time at every bus (using the fault current values), identifies corrections that reduce clearing times, and recommends setting changes
- The incident energy analysis uses both the fault current and the cleared time to calculate the energy released at each location
Delivering any one of these without the others produces an incomplete and less reliable result. An arc flash study without a short circuit analysis has no verified fault current input. An arc flash study without a coordination study has no verified clearing time input — the most important variable in the incident energy calculation.
When reviewing proposals, confirm explicitly that all three analyses are in scope. If a provider’s proposal refers only to “arc flash calculations” or “arc flash hazard analysis” without mentioning short circuit and coordination, ask directly whether those analyses are included and get the answer confirmed in writing before signing.
For a complete overview of what a properly scoped arc flash study involves and what the deliverables should include, see our arc flash study guide. For a cost estimate that reflects the complete three-analysis scope, use our free cost estimator.