Section 3: Appendices C: Coordination Curves
The coordination study calculates how the overcurrent devices in the system will interact with each other under various overload or fault conditions. On the graphs, current is shown on the horizontal axis and time is on the vertical axis. Note that each curve is plotted at a reference voltage of 480V even though some devices may be rated for higher or lower voltages. Progressing from left to right on the horizontal axis, the fault or overload current is increased. Trip times are calculated by finding the correct fault or overload condition on the horizontal axis and moving vertically upward until a protective device curve is intercepted. These trip times can be adjusted either by making changes to the settings on the adjustable breakers or by using a different size and style of fixed-magnitude breaker or fuse. By adjusting these trip times, the system can be coordinated so that if a fault does occur, the fewest pieces of equipment possible are shut down. Example: If a fault would happen at a motor, you would want the individual breaker or fuse in the starter bucket to open and shut that motor down. You would not want the main breaker to open and shut down the entire MCC. Proper settings minimize the probability of this occurring. A listing of the settings and sizes of the breakers included in this study can be found in Table 4: Protective Device Setting Report . Not all curves are shown in this appendix because there were no coordination issues or no recommendations made for changes to coordination settings.
If any recommendations for new breaker settings have been made, they can be found in Table 1: Recommendations .
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