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The following table shows the setting ranges of the curve defining constants.
Curve defining constants
k
a
c
kr
b
IEC/UK Inverse Curves
(Time Multiplier = 1)
1000
100
10
1
0.1
1
10
Current (Multiple of Setting)
Programmable Reset Characteristics
OC1, EF1 and SEF1 have a programmable reset feature: instantaneous, definite time delayed, or
dependent time delayed reset. (Refer to Appendix A for a more detailed description.)
Instantaneous resetting is normally applied in multi-shot auto-reclosing schemes, to ensure correct
grading between relays at various points in the scheme.
The inverse reset characteristic is particularly useful for providing correct coordination with an
upstream induction disc type overcurrent relay.
The definite time delayed reset characteristic may be used to provide faster clearance of
intermittent ('pecking' or 'flashing') fault conditions.
Range
0.000 – 30.000
0.00 – 5.00
0.000 – 5.000
0.000 – 30.000
0.00 – 5.00
IEEE/US Inverse Curves
100
10
LTI
NI
1
VI
EI
0.1
100
1
Figure 2.1.3
IDMT Characteristics
⎯
⎯
12
Step
0.001
0.01
0.001
0.001
0.01
(Time Multiplier = 1)
10
Current (Multiple of Setting)
6 F 2 S 0 7 5 8
MI
VI
CO2
CO8
EI
100
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