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CHAPTER 6: SETPOINTS
339 MOTOR PROTECTION SYSTEM – INSTRUCTION MANUAL
Multiplier (TDM)
Current (I/Ipickup)
1.5
2.0
1.00
27.000 13.500 6.750
IEC Curve C
0.05
3.200
1.333
0.10
6.400
2.667
0.20
12.800 5.333
0.40
25.600 10.667 4.000
0.60
38.400 16.000 6.000
0.80
51.200 21.333 8.000
1.00
64.000 26.667 10.000 5.333
IEC Short Time
0.05
0.153
0.089
0.10
0.306
0.178
0.20
0.612
0.356
0.40
1.223
0.711
0.60
1.835
1.067
0.80
2.446
1.423
1.00
3.058
1.778
IAC Curves
The curves for the General Electric type IAC relay family are derived from the formulae:
where: T = trip time (seconds), M = multiplier setpoint, I = input current, I
setpoint, A to E = constants.
Table 6-7: GE Type IAC Inverse Curve Constants
IAC Curve Shape
IAC Extreme Inverse
IAC Very Inverse
IAC Inverse
IAC Short Inverse
Table 6-8: IAC Curve Trip Times
Multiplier (TDM)
1.5
2.0
IAC Extremely Inverse
0.5
1.699
0.749
1.0
3.398
1.498
2.0
6.796
2.997
4.0
13.591 5.993
6.0
20.387 8.990
8.0
27.183 11.987 4.846
10.0
33.979 14.983 6.058
IAC Very Inverse
0.5
1.451
0.656
3.0
4.0
5.0
4.500
3.375
0.500
0.267
0.167
1.000
0.533
0.333
2.000
1.067
0.667
2.133
1.333
3.200
2.000
4.267
2.667
3.333
0.056
0.044
0.038
0.111
0.088
0.075
0.223
0.175
0.150
0.445
0.351
0.301
0.668
0.526
0.451
0.890
0.702
0.602
1.113
0.877
0.752
A
B
C
0.0040
0.6379
0.6200
0.0900
0.7955
0.1000
0.2078
0.8630
0.8000
0.0428
0.0609
0.6200
3.0
4.0
5.0
0.303
0.178
0.123
0.606
0.356
0.246
1.212
0.711
0.491
2.423
1.422
0.983
3.635
2.133
1.474
2.844
1.966
3.555
2.457
0.269
0.172
0.133
S3 PROTECTION
6.0
7.0
8.0
9.0
2.700
2.250
1.929
1.688
0.114
0.083
0.063
0.050
0.229
0.167
0.127
0.100
0.457
0.333
0.254
0.200
0.914
0.667
0.508
0.400
1.371
1.000
0.762
0.600
1.829
1.333
1.016
0.800
2.286
1.667
1.270
1.000
0.034
0.031
0.029
0.027
0.067
0.062
0.058
0.054
0.135
0.124
0.115
0.109
0.269
0.247
0.231
0.218
0.404
0.371
0.346
0.327
0.538
0.494
0.461
0.435
0.673
0.618
0.576
0.544
= pickup current
pu
D
E
1.7872
0.2461
–1.2885
7.9586
–0.4180
0.1947
–0.0010
0.0221
6.0
7.0
8.0
9.0
0.093
0.074
0.062
0.053
0.186
0.149
0.124
0.106
0.372
0.298
0.248
0.212
0.744
0.595
0.495
0.424
1.115
0.893
0.743
0.636
1.487
1.191
0.991
0.848
1.859
1.488
1.239
1.060
0.113
0.101
0.093
0.087
10.0
1.500
0.040
0.081
0.162
0.323
0.485
0.646
0.808
0.026
0.052
0.104
0.207
0.311
0.415
0.518
Eq. 19
10.0
0.046
0.093
0.185
0.370
0.556
0.741
0.926
0.083
6–69
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