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CHAPTER 4: SETPOINTS
MULTIPLIER
CURRENT (I/Ipickup)
(TDM)
1.5
4.0
12.537
6.0
18.805
8.0
25.073
10.0
31.341
ANSI NORMALLY INVERSE
0.5
2.142
1.0
4.284
2.0
8.568
4.0
17.137
6.0
25.705
8.0
34.274
10.0
42.842
ANSI MODERATELY INVERSE
0.5
0.675
1.0
1.351
2.0
2.702
4.0
5.404
6.0
8.106
8.0
10.807
10.0
13.509
869 MOTOR PROTECTION SYSTEM – INSTRUCTION MANUAL
2.0
3.0
4.0
5.301
2.148
1.365
7.951
3.221
2.047
10.602
4.295
2.730
13.252
5.369
3.412
0.883
0.377
0.256
1.766
0.754
0.513
3.531
1.508
1.025
7.062
3.016
2.051
10.594
4.524
3.076
14.125
6.031
4.102
17.656
7.539
5.127
0.379
0.239
0.191
0.757
0.478
0.382
1.515
0.955
0.764
3.030
1.910
1.527
4.544
2.866
2.291
6.059
3.821
3.054
7.574
4.776
3.818
IEC CURVES
For European applications, the relay offers three standard curves defined in IEC 255-4 and
British standard BS142. These are defined as IEC Curve A, IEC Curve B, and IEC Curve C. The
formula for these curves is:
Where:
T = operate time (in seconds)
TDM = Multiplier setting
I = input current
I
= Pickup Current setting
pickup
K, E = constants
t
= characteristic constant
r
T
= reset time in seconds (assuming energy capacity is 100% and RESET is
RESET
"Timed")
Table 4-24: IEC (BS) INVERSE TIME CURVE CONSTANTS
IEC (BS) CURVE SHAPE
IEC Curve A (BS142)
IEC Curve B (BS142)
IEC Curve C (BS142)
IEC Short Inverse
5.0
6.0
7.0
1.040
0.864
0.755
1.559
1.297
1.133
2.079
1.729
1.510
2.599
2.161
1.888
0.203
0.172
0.151
0.407
0.344
0.302
0.814
0.689
0.604
1.627
1.378
1.208
2.441
2.067
1.812
3.254
2.756
2.415
4.068
3.445
3.019
0.166
0.151
0.141
0.332
0.302
0.281
0.665
0.604
0.563
1.329
1.208
1.126
1.994
1.812
1.689
2.659
2.416
2.252
3.324
3.020
2.815
K
E
0.140
0.020
13.500
1.000
80.000
2.000
0.050
0.040
PROTECTION
8.0
9.0
10.0
0.680
0.625
0.583
1.020
0.937
0.874
1.360
1.250
1.165
1.700
1.562
1.457
0.135
0.123
0.113
0.270
0.246
0.226
0.541
0.492
0.452
1.082
0.983
0.904
1.622
1.475
1.356
2.163
1.967
1.808
2.704
2.458
2.260
0.133
0.128
0.123
0.267
0.255
0.247
0.533
0.511
0.493
1.066
1.021
0.986
1.600
1.532
1.479
2.133
2.043
1.972
2.666
2.554
2.465
t
r
9.7
43.2
58.2
0.500
4–175
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