Protective Device Coordination studies are required to insure the safety of the public, working personnel and that equipment is not damaged under fault conditions per the requirements of NEC 110-10. Analysis of TCC (Time Current Characteristics) data for the protective devices and equipment such as transformers and cable is used to permit the circuit-protective devices to clear a fault without extensive damage to the electrical components of the circuit.
There is a second type of coordination, known as Selective Coordination which uses the TCC curves to insure that faults (short circuits) affect the least possible portion of the electrical distribution system. Improper selective coordination or no selective coordination can result in faults on branch circuits shutting down complete production lines, whole restaurants, wings of hotels, schools and institutions. Such undesirable events result in loss of production, loss of business income, inconvenience to customers and risk of injury. These losses can be minimized or completely eliminated by proper Selective Coordination. Selective Coordination is a second benefit of performing a coordination study.
Note that Selective Coordination, unlike Coordination, is not a requirement of the National Electrical Code (except for elevators, 620-62 and Healthcare, 517-17 on ground fault).
Protective Device Coordination studies provided by PAA are complete with one-line diagrams, device rating evaluations, protective equipment setting reports and engineering analysis and commentary. Contact us in advance of your system design if you want to discuss the equipment options available with relays, breakers and fuses for obtaining Selective Coordination.
For all Selective Coordination Studies each regional office of PAA uses the latest SKM version of CAPTOR. New TCC response curves for protective devices are continually added from SKM. SKM is an international leader in Electrical Systems Analysis software. All PAA Engineers are graduates of SKM training.