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There is a second type of coordination, known as Selective Coordination
which uses the TCC curves to ensure 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 operations for parts or possibly
a whole building, manufacturing facilities. 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, the second benefit of performing a coordination
study.
Correct setting values can only be determined by a study based on all
the pertinent electrical characteristics of the equipment in the system.
SUGGESTED SERVICES FOR A COORDINATION DEVICE STUDY
- Protective device coordination / evaluation
- Description, purpose, basis and scope of the study plus a simplified
single-line diagram of the portion of the power system which is included
within the scope of study.
- Tabulations of circuit breaker, fuse and other equipment ratings versus
calculated short-circuit duties and commentary regarding same.
- Protective device time versus current coordination curves, tabulations
of relay and circuit breaker trip settings, fuse selection and commentary
regarding same.
- Fault-current tabulations including a definition of terms and a guide
for interpretation.
- Tabulation of appropriate tap settings for relay seal-in units.
- Relay Settings.
- Determine the correct protective device settings so that your system
will be 100% protected
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