CHAPTER 6: SETPOINTS
S3 PROTECTION
345 TRANSFORMER PROTECTION SYSTEM – INSTRUCTION MANUAL
6–85
Table 7: IEC (BS) Inverse Time Curve Constants
Table 8: IEC Curve Trip Times (in seconds)
IAC Curves
The curves for the General Electric type IAC relay family are derived from the formulae:
Eq. 15
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
1.00
27.000 13.500 6.750 4.500 3.375 2.700 2.250 1.929 1.688 1.500
IEC Curve C
0.05
3.200 1.333 0.500 0.267 0.167 0.114 0.083 0.063 0.050 0.040
0.10
6.400 2.667 1.000 0.533 0.333 0.229 0.167 0.127 0.100 0.081
0.20
12.800 5.333 2.000 1.067 0.667 0.457 0.333 0.254 0.200 0.162
0.40
25.600 10.667 4.000 2.133 1.333 0.914 0.667 0.508 0.400 0.323
0.60
38.400 16.000 6.000 3.200 2.000 1.371 1.000 0.762 0.600 0.485
0.80
51.200 21.333 8.000 4.267 2.667 1.829 1.333 1.016 0.800 0.646
1.00
64.000 26.667 10.000 5.333 3.333 2.286 1.667 1.270 1.000 0.808
IEC Short Time
0.05
0.153 0.089 0.056 0.044 0.038 0.034 0.031 0.029 0.027 0.026
0.10
0.306 0.178 0.111 0.088 0.075 0.067 0.062 0.058 0.054 0.052
0.20
0.612 0.356 0.223 0.175 0.150 0.135 0.124 0.115 0.109 0.104
0.40
1.223 0.711 0.445 0.351 0.301 0.269 0.247 0.231 0.218 0.207
0.60
1.835 1.067 0.668 0.526 0.451 0.404 0.371 0.346 0.327 0.311
0.80
2.446 1.423 0.890 0.702 0.602 0.538 0.494 0.461 0.435 0.415
1.00
3.058 1.778 1.113 0.877 0.752 0.673 0.618 0.576 0.544 0.518