Page 8-3
IL17569
Effective June, 2001
Table 8.1 Constants for Inverse Time Overcurrent Curves
CALCULATED CURVES
Curve Type P A B t
r
ANSI/IEEE
Moderately Inverse 0.02 0.0515 0.114 4.85
Very Inverse 2 19.61 0.491 21.6
Extremely Inverse 2 28.2 0.1217 29.1
IEC
1
IEC-A 0.02 0.14 0 0.14
IEC-B 1 13.5 0 13.5
IEC-C 2 80 0 80
1 FP-5000 does not directly provide IEC-D, IEC-E and IEC-F curves. In the latest IEC standard, IEC-D, IEC-E and IEC-F are the same as
ANSI Moderately Inverse, Very Inverse and Extremely Inverse, respectively.
8.3.3 Curve Shapes
The FP-5000 Protective Relay provides circuit breakers with an extensive degree of selective coordination potential, and permits curve
shaping over a wide range. The available pickup settings, which are inverse time overcurrent time multiplier settings, and inverse time
overcurrent (phase and ground) curve selections are addressed with respect to their effect on the resultant characteristic curve described
above. The operating characteristics of the relay are graphically represented by time-current characteristic curves shown in Figure 8-4, below.
Figure 8-4. FP-5000 Time-Current Characteristic Curves
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