Protective Device Coordination Study Services

A protective device coordination study evaluates and adjusts your protective device settings with the goal of having the device closest to a fault clear first, minimizing unnecessary upstream outages. When it works well, a fault on one branch takes out that branch, not half your facility.

Without coordination, a fault that should have tripped one breaker can cascade upstream and drop equipment that had nothing to do with the problem. That is lost production, and it is avoidable.

What a Coordination Study Delivers

• Time current characteristic (TCC) curves for your protective devices
• Recommended protective device settings to improve coordination and selectivity
• A selectivity analysis showing which devices coordinate and where gaps exist
• Settings that also feed accurate clearing times into your arc flash study

A Common Situation

The most frequent reason a client calls for coordination work is nuisance tripping, and it is often blamed on the wrong thing.

I have been called out to facilities where equipment was tripping and everyone assumed a breaker had been sized wrong. The client was ready to blame the design. When I looked at it, the contractor had installed the breakers and left them at factory default settings. No coordination study had ever been performed, so nothing was set to work with anything else. Once the settings were adjusted against the other devices and against motor inrush, the tripping stopped.

The breaker was never the problem. Nobody had coordinated it. I cover more of these in 10 problems I commonly find when reviewing existing arc flash studies.

When You Need One

• Nuisance tripping, or outages larger than they should be
• New equipment or a service change that alters your protection scheme
• Facilities where an outage on one circuit cannot be allowed to drop others
• After a short circuit study, to set the devices the study evaluated
• Where selective coordination is required by the applicable electrical code

What You Get

A coordination study report with TCC curves, recommended protective device settings, and a selectivity analysis. The analysis is prepared under the responsible charge of a licensed Professional Engineer, with sealing as required by the applicable jurisdiction. Where the study is performed alongside an arc flash study, the clearing times feed directly into the incident energy calculations.

Part of a Complete Power System Study

Coordination builds on the short circuit study, which establishes the fault current the devices have to handle, and it feeds the arc flash study, where clearing time drives the incident energy. We perform these analyses individually where appropriate, or together as part of a complete power system study.