GE 339

6–68 339 MOTOR PROTECTION SYSTEM – INSTRUCTION MANUAL
S3 PROTECTION CHAPTER 6: SETPOINTS
IEC Curves
For European applications, the relay offers the four standard curves defined in IEC 255-4
and British standard BS142. These are defined as IEC Curve A, IEC Curve B, IEC Curve C, and
Short Inverse. The formulae for these curves are:
Eq. 18
where: T = trip time (seconds), M = multiplier setpoint, I = input current, I
pu
= pickup current
setpoint, K, E = constants.
Table 6-5: IEC (BS) Inverse Time Curve Constants
Table 6-6: IEC Curve Trip Times (in seconds)
8.0 34.274 14.125 6.031 4.102 3.254 2.756 2.415 2.163 1.967 1.808
10.0 42.842 17.656 7.539 5.127 4.068 3.445 3.019 2.704 2.458 2.260
ANSI Moderately Inverse
0.5 0.675 0.379 0.239 0.191 0.166 0.151 0.141 0.133 0.128 0.123
1.0 1.351 0.757 0.478 0.382 0.332 0.302 0.281 0.267 0.255 0.247
2.0 2.702 1.515 0.955 0.764 0.665 0.604 0.563 0.533 0.511 0.493
4.0 5.404 3.030 1.910 1.527 1.329 1.208 1.126 1.066 1.021 0.986
6.0 8.106 4.544 2.866 2.291 1.994 1.812 1.689 1.600 1.532 1.479
8.0 10.807 6.059 3.821 3.054 2.659 2.416 2.252 2.133 2.043 1.972
10.0 13.509 7.574 4.776 3.818 3.324 3.020 2.815 2.666 2.554 2.465
IEC (BS) Curve Shape K E
IEC Curve A (BS142) 0.140 0.020
IEC Curve B (BS142) 13.500 1.000
IEC Curve C (BS142) 80.000 2.000
IEC Short Inverse 0.050 0.040
Multiplier (TDM) Current (I/Ipickup)
1.5 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0
IEC Curve A
0.05 0.860 0.501 0.315 0.249 0.214 0.192 0.176 0.165 0.156 0.149
0.10 1.719 1.003 0.630 0.498 0.428 0.384 0.353 0.330 0.312 0.297
0.20 3.439 2.006 1.260 0.996 0.856 0.767 0.706 0.659 0.623 0.594
0.40 6.878 4.012 2.521 1.992 1.712 1.535 1.411 1.319 1.247 1.188
0.60 10.317 6.017 3.781 2.988 2.568 2.302 2.117 1.978 1.870 1.782
0.80 13.755 8.023 5.042 3.984 3.424 3.070 2.822 2.637 2.493 2.376
1.00 17.194 10.029 6.302 4.980 4.280 3.837 3.528 3.297 3.116 2.971
IEC Curve B
0.05 1.350 0.675 0.338 0.225 0.169 0.135 0.113 0.096 0.084 0.075
0.10 2.700 1.350 0.675 0.450 0.338 0.270 0.225 0.193 0.169 0.150
0.20 5.400 2.700 1.350 0.900 0.675 0.540 0.450 0.386 0.338 0.300
0.40 10.800 5.400 2.700 1.800 1.350 1.080 0.900 0.771 0.675 0.600
0.60 16.200 8.100 4.050 2.700 2.025 1.620 1.350 1.157 1.013 0.900
0.80 21.600 10.800 5.400 3.600 2.700 2.160 1.800 1.543 1.350 1.200
Multiplier (TDM) Current (I/Ipickup)
1.5 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0