UFC 3 -520-01
June 10, 2002
instantaneous breaker trip. Coordination within the breaker's instantaneous trip region
means that the fuse must exhibit current-limiting characteristics.
Figure 9-2. Selective Coordination Example with Fuses
10000
5000
2000
1000
Line Side
500
MCCB
200
100
50
20
10
5
2
1
Fuse A
.5
Clearing
Curve
.2
.1
Fuse B
Clearing
.05
Curve
.02
.01
200
100
200
500
1000
2000
5000
100
500
1000
Current (Amperes at 480 Volts)
9-2.5.5 Figures 9-1 and 9 -2 only s how a portion of the electrical system for the sake
of clarity in the examples. For an actual coordination study, provide the coordination
curves for all components in series, from the lowest evaluated voltage upstream to the
next level beyond the service entrance, usually the feeder serving the building service
9-2.6
Coordination Analysis .
9-2.6.1 Protective device coordination requires a careful evaluation of the electrical
system under various operating conditions. Perform the following steps to verify the
protective coordination throughout the electrical system.
9-2.6.2
Obtain the following system information:
System one-line diagram.
9-8
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