Protective device coordination that isolates a fault to the nearest device.
Time-current analysis and device settings so a fault trips the device closest to it and the rest of the system stays energized.
When a fault occurs, only the protective device immediately upstream of it should open. If a device further upstream trips first, a localized fault takes down a far larger portion of the building than it needed to, which in a hospital, a data center, or a manufacturing facility is the difference between an inconvenience and an incident.
A coordination study models the system and plots the time-current characteristics of every protective device in series. Where curves overlap, the devices can trip in the wrong order, and the study identifies exactly where that happens and what settings resolve it.
Selective coordination is mandatory for certain systems under the NEC, including emergency and legally required standby systems. Those paths are analyzed specifically against that requirement rather than treated as ordinary distribution, and the documentation is prepared so a reviewer can verify it.
What it covers
- Time-current coordination analysis
- Selective coordination for emergency systems
- Relay and breaker setting recommendations
- Time-current curve (TCC) plots
- NEC selective coordination compliance
- Coordination with the short circuit study
Coordination study report
The analysis with modeling assumptions, sealed by a licensed professional engineer.
TCC curve plots
Time-current curves for each series of protective devices, showing the coordination achieved.
Device settings schedule
Recommended settings for every adjustable device, ready to be applied in the field.
Selective coordination documentation
Where the NEC requires selective coordination, the evidence a reviewer needs to verify it.
Sectors served
Coordination Studies sealed by a professional engineer, in 22 states.
See where we are licensedCoordination Studies: common questions.
What is a protective device coordination study?
A coordination study analyzes how the protective devices in an electrical system behave relative to each other when a fault occurs. By plotting each device's time-current characteristic, it confirms that the device nearest the fault opens first, so the fault is isolated and the rest of the system stays energized.
What is the difference between coordination and selective coordination?
Coordination is the general goal of having the closest upstream device clear a fault first. Selective coordination is the stricter requirement that this holds for the full range of overcurrents and times, which the NEC mandates for emergency systems, legally required standby systems, and certain other critical paths.
Do I need a coordination study and a short circuit study?
They work together. The short circuit study establishes the available fault current at each point, which is the input a coordination study needs to evaluate how devices will behave. Vertical Design Services commonly performs both together, along with an arc flash study, since all three draw on the same system model.
What are TCC curves?
Time-current characteristic curves plot how long each protective device takes to operate at a given level of current. Plotting devices in series on the same graph shows visually whether they coordinate: curves that overlap indicate the devices can trip in the wrong order.
Need coordination studies on a project?
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