CHAPTER 6: SETPOINTS S3 PROTECTION350 FEEDER PROTECTION SYSTEM – INSTRUCTION MANUAL 6–27IEC CurvesFor European applications, the relay offers the four standard curves defined in IEC 255-4and British standard BS142. These are defined as IEC Curve A, IEC Curve B, IEC Curve C, andShort Inverse. The formulae for these curves are:where: T = trip time (seconds), M = multiplier setpoint, I = input current, I pu = pickup currentsetpoint, K, E = constants.Table 5: IEC (BS) Inverse Time Curve ConstantsTable 6: IEC Curve Trip Times (in seconds)ANSI Moderately Inverse0.5 0.675 0.379 0.239 0.191 0.166 0.151 0.141 0.133 0.128 0.1231.0 1.351 0.757 0.478 0.382 0.332 0.302 0.281 0.267 0.255 0.2472.0 2.702 1.515 0.955 0.764 0.665 0.604 0.563 0.533 0.511 0.4934.0 5.404 3.030 1.910 1.527 1.329 1.208 1.126 1.066 1.021 0.9866.0 8.106 4.544 2.866 2.291 1.994 1.812 1.689 1.600 1.532 1.4798.0 10.807 6.059 3.821 3.054 2.659 2.416 2.252 2.133 2.043 1.97210.0 13.509 7.574 4.776 3.818 3.324 3.020 2.815 2.666 2.554 2.465IEC (BS) Curve Shape K EIEC Curve A (BS142) 0.140 0.020IEC Curve B (BS142) 13.500 1.000IEC Curve C (BS142) 80.000 2.000IEC Short Inverse 0.050 0.040Multiplier (TDM) Current (I/Ipickup)1.5 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0IEC Curve A0.05 0.860 0.501 0.315 0.249 0.214 0.192 0.176 0.165 0.156 0.1490.10 1.719 1.003 0.630 0.498 0.428 0.384 0.353 0.330 0.312 0.2970.20 3.439 2.006 1.260 0.996 0.856 0.767 0.706 0.659 0.623 0.5940.40 6.878 4.012 2.521 1.992 1.712 1.535 1.411 1.319 1.247 1.1880.60 10.317 6.017 3.781 2.988 2.568 2.302 2.117 1.978 1.870 1.7820.80 13.755 8.023 5.042 3.984 3.424 3.070 2.822 2.637 2.493 2.3761.00 17.194 10.029 6.302 4.980 4.280 3.837 3.528 3.297 3.116 2.971IEC Curve B0.05 1.350 0.675 0.338 0.225 0.169 0.135 0.113 0.096 0.084 0.0750.10 2.700 1.350 0.675 0.450 0.338 0.270 0.225 0.193 0.169 0.1500.20 5.400 2.700 1.350 0.900 0.675 0.540 0.450 0.386 0.338 0.3000.40 10.800 5.400 2.700 1.800 1.350 1.080 0.900 0.771 0.675 0.6000.60 16.200 8.100 4.050 2.700 2.025 1.620 1.350 1.157 1.013 0.9000.80 21.600 10.800 5.400 3.600 2.700 2.160 1.800 1.543 1.350 1.2001.00 27.000 13.500 6.750 4.500 3.375 2.700 2.250 1.929 1.688 1.500IEC Curve C0.05 3.200 1.333 0.500 0.267 0.167 0.114 0.083 0.063 0.050 0.040Multiplier (TDM) Current (I/Ipickup)1.5 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0