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6–86
345 TRANSFORMER PROTECTION SYSTEM – INSTRUCTION MANUAL
S3 PROTECTION
CHAPTER 6: SETPOINTS
where: T = trip time (seconds), M = multiplier setpoint, I = input current, I
pu
= pickup current
setpoint, A to E = constants.
Table 9: GE Type IAC Inverse Curve Constants
Table 10: IAC Curve Trip Times
PHASE TIMED OVERCURRENT PROTECTION
The SR345 relay has two Phase Time Overcurrent elements per protection group. The
settings of this function are applied to each of the three phases to produce phase
overcurrent trip or pickup. There is no intentional “dead band” where the current is above
IAC Curve Shape
A
B
C
D
E
IAC Extreme Inverse
0.0040
0.6379
0.6200
1.7872
0.2461
IAC Very Inverse
0.0900
0.7955
0.1000
–1.2885
7.9586
IAC Inverse
0.2078
0.8630
0.8000
–0.4180
0.1947
IAC Short Inverse
0.0428
0.0609
0.6200
–0.0010
0.0221
Multiplier (TDM)
1.5
2.0
3.0
4.0
5.0
6.0
7.0
8.0
9.0
10.0
IAC Extremely Inverse
0.5
1.699 0.749 0.303 0.178 0.123 0.093 0.074 0.062 0.053 0.046
1.0
3.398 1.498 0.606 0.356 0.246 0.186 0.149 0.124 0.106 0.093
2.0
6.796 2.997 1.212 0.711 0.491 0.372 0.298 0.248 0.212 0.185
4.0
13.591 5.993 2.423 1.422 0.983 0.744 0.595 0.495 0.424 0.370
6.0
20.387 8.990 3.635 2.133 1.474 1.115 0.893 0.743 0.636 0.556
8.0
27.183 11.987 4.846 2.844 1.966 1.487 1.191 0.991 0.848 0.741
10.0
33.979 14.983 6.058 3.555 2.457 1.859 1.488 1.239 1.060 0.926
IAC Very Inverse
0.5
1.451 0.656 0.269 0.172 0.133 0.113 0.101 0.093 0.087 0.083
1.0
2.901 1.312 0.537 0.343 0.266 0.227 0.202 0.186 0.174 0.165
2.0
5.802 2.624 1.075 0.687 0.533 0.453 0.405 0.372 0.349 0.331
4.0
11.605 5.248 2.150 1.374 1.065 0.906 0.810 0.745 0.698 0.662
6.0
17.407 7.872 3.225 2.061 1.598 1.359 1.215 1.117 1.046 0.992
8.0
23.209 10.497 4.299 2.747 2.131 1.813 1.620 1.490 1.395 1.323
10.0
29.012 13.121 5.374 3.434 2.663 2.266 2.025 1.862 1.744 1.654
IAC Inverse
0.5
0.578 0.375 0.266 0.221 0.196 0.180 0.168 0.160 0.154 0.148
1.0
1.155 0.749 0.532 0.443 0.392 0.360 0.337 0.320 0.307 0.297
2.0
2.310 1.499 1.064 0.885 0.784 0.719 0.674 0.640 0.614 0.594
4.0
4.621 2.997 2.128 1.770 1.569 1.439 1.348 1.280 1.229 1.188
6.0
6.931 4.496 3.192 2.656 2.353 2.158 2.022 1.921 1.843 1.781
8.0
9.242 5.995 4.256 3.541 3.138 2.878 2.695 2.561 2.457 2.375
10.0
11.552 7.494 5.320 4.426 3.922 3.597 3.369 3.201 3.072 2.969
IAC Short Inverse
0.5
0.072 0.047 0.035 0.031 0.028 0.027 0.026 0.026 0.025 0.025
1.0
0.143 0.095 0.070 0.061 0.057 0.054 0.052 0.051 0.050 0.049
2.0
0.286 0.190 0.140 0.123 0.114 0.108 0.105 0.102 0.100 0.099
4.0
0.573 0.379 0.279 0.245 0.228 0.217 0.210 0.204 0.200 0.197
6.0
0.859 0.569 0.419 0.368 0.341 0.325 0.314 0.307 0.301 0.296
8.0
1.145 0.759 0.559 0.490 0.455 0.434 0.419 0.409 0.401 0.394
10.0
1.431 0.948 0.699 0.613 0.569 0.542 0.524 0.511 0.501 0.493