5-208 M60 MOTOR PROTECTION SYSTEM – INSTRUCTION MANUALGROUPED ELEMENTS CHAPTER 5: SETTINGS5 IEC curvesFor European applications, the relay offers three standard curves defined in IEC 255-4 and British standard BS142. Theseare defined as IEC Curve A, IEC Curve B, and IEC Curve C. The formulae for these curves are:, Eq. 5-32whereT = operate time (in seconds)TDM = Multiplier settingI = input currentIpickup = Pickup Current settingK, E = constantstr = characteristic constantTRESET = reset time in seconds (assuming energy capacity is 100% and RESET is “Timed”)Table 5-28: IEC (BS) inverse time curve constants4.0 90.727 38.087 14.587 8.007 5.187 3.710 2.837 2.277 1.897 1.6266.0 136.090 57.130 21.880 12.010 7.780 5.564 4.255 3.416 2.845 2.4398.0 181.454 76.174 29.174 16.014 10.374 7.419 5.674 4.555 3.794 3.25210.0 226.817 95.217 36.467 20.017 12.967 9.274 7.092 5.693 4.742 4.065IEEE Very Inverse0.5 8.090 3.514 1.471 0.899 0.654 0.526 0.450 0.401 0.368 0.3451.0 16.179 7.028 2.942 1.798 1.308 1.051 0.900 0.802 0.736 0.6892.0 32.358 14.055 5.885 3.597 2.616 2.103 1.799 1.605 1.472 1.3784.0 64.716 28.111 11.769 7.193 5.232 4.205 3.598 3.209 2.945 2.7566.0 97.074 42.166 17.654 10.790 7.849 6.308 5.397 4.814 4.417 4.1348.0 129.432 56.221 23.538 14.387 10.465 8.410 7.196 6.418 5.889 5.51310.0 161.790 70.277 29.423 17.983 13.081 10.513 8.995 8.023 7.361 6.891IEEE Moderately Inverse0.5 3.220 1.902 1.216 0.973 0.844 0.763 0.706 0.663 0.630 0.6031.0 6.439 3.803 2.432 1.946 1.688 1.526 1.412 1.327 1.260 1.2072.0 12.878 7.606 4.864 3.892 3.377 3.051 2.823 2.653 2.521 2.4144.0 25.756 15.213 9.729 7.783 6.753 6.102 5.647 5.307 5.041 4.8276.0 38.634 22.819 14.593 11.675 10.130 9.153 8.470 7.960 7.562 7.2418.0 51.512 30.426 19.458 15.567 13.507 12.204 11.294 10.614 10.083 9.65410.0 64.390 38.032 24.322 19.458 16.883 15.255 14.117 13.267 12.604 12.068IEC (BS) curve shape K E trIEC Curve A (BS142) 0.140 0.020 9.7IEC Curve B (BS142) 13.500 1.000 43.2IEC Curve C (BS142) 80.000 2.000 58.2IEC Short Inverse 0.050 0.040 0.500Multiplier(TDM)Current ( I / I pickup)1.5 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0T TDMKI I pickup E 1–-----------------------------------= T RESET TDMt r1 I I pickup 2–-----------------------------------=
