CHAPTER 5: SETTINGS GROUPED ELEMENTSC70 CAPACITOR BANK PROTECTION AND CONTROL SYSTEM – INSTRUCTION MANUAL 5-1695IEC 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 IEC curves are derived by the operate and reset timeequations.Eq. 5-8whereT = operate time (in seconds)TDM = Multiplier settingI = input currentIpickup = Pickup Current settingK, E = constants defined in the tabletr = characteristic constant defined in the tableTRESET = reset time in seconds (assuming energy capacity is 100% and RESET is “Timed”)Table 5-26: IEC (BS) inverse time curve constantsTable 5-27: IEC curve trip times (in seconds)4.0 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 10.0IEC 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 2.376Multiplier(TDM)Current ( I / I pickup)1.5 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0
