PROTECTIVE DEVICE COORDINATION STUDIES

A Protective Device Coordination Study determines the optimal settings of relays and circuit breakers and fuse sizes to ensure that the breaker or fuse closest to an electrical fault will open.

What may happen if my system is not coordinated?

• Multiple devices in series may open simultaneously in the event of a fault, resulting in an unnecessary blackout condition for the rest of the system.

• Emergency life safety egress lighting may fail in the event of fault.

• Unscheduled production down time.

• Unorderly shut down of industrial manufacturing or continuous processes.

Where is device coordination required?

• Emergency systems

• Life safety equipment

• Elevators

• Health care facilities

• Critical operations power systems

How is coordination improved or ensured?

• Create time current curves (TCCs) to graphically evaluate the protective devices in series.

• Reference each manufacturer’s published selective coordination charts and documentation.

• Modify relay or breaker settings to optimal settings.

• Recommend specific fuse sizes and types for selective coordination.

• Make equipment recommendations during the design phase.