CHAPTER 5: SETTINGS
GROUPED ELEMENTS
F35 MULTIPLE FEEDER PROTECTION SYSTEM – INSTRUCTION MANUAL
5-229
5
IEEE curves
The IEEE time overcurrent curve shapes conform to industry standards and the IEEE C37.112-1996 curve classifications for
extremely, very, and moderately inverse curves. The IEEE curves are derived from the operate and reset time equations.
Eq. 5-8
where
T = operate time (in seconds)
TDM = Multiplier setting
I = input current
I
pickup
= Pickup Current setting
A, B, p = constants defined in the table
T
RESET
= reset time in seconds (assuming energy capacity is 100% and RESET is “Timed”)
t
r
= characteristic constant defined in the table
Table 5-27: IEEE inverse time curve constants
Table 5-28: IEEE curve trip times (in seconds)
IEEE curve shape
A
B
p
t
r
IEEE Extremely Inverse
28.2
0.1217
2.0000
29.1
IEEE Very Inverse
19.61
0.491
2.0000
21.6
IEEE Moderately Inverse
0.0515
0.1140
0.02000
4.85
Multiplier
(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
IEEE Extremely Inverse
0.5
11.341
4.761
1.823
1.001
0.648
0.464
0.355
0.285
0.237
0.203
1.0
22.682
9.522
3.647
2.002
1.297
0.927
0.709
0.569
0.474
0.407
2.0
45.363
19.043
7.293
4.003
2.593
1.855
1.418
1.139
0.948
0.813
4.0
90.727
38.087
14.587
8.007
5.187
3.710
2.837
2.277
1.897
1.626
6.0
136.090
57.130
21.880
12.010
7.780
5.564
4.255
3.416
2.845
2.439
8.0
181.454
76.174
29.174
16.014
10.374
7.419
5.674
4.555
3.794
3.252
10.0
226.817
95.217
36.467
20.017
12.967
9.274
7.092
5.693
4.742
4.065
IEEE Very Inverse
0.5
8.090
3.514
1.471
0.899
0.654
0.526
0.450
0.401
0.368
0.345
1.0
16.179
7.028
2.942
1.798
1.308
1.051
0.900
0.802
0.736
0.689
2.0
32.358
14.055
5.885
3.597
2.616
2.103
1.799
1.605
1.472
1.378
4.0
64.716
28.111
11.769
7.193
5.232
4.205
3.598
3.209
2.945
2.756
6.0
97.074
42.166
17.654
10.790
7.849
6.308
5.397
4.814
4.417
4.134
8.0
129.432
56.221
23.538
14.387
10.465
8.410
7.196
6.418
5.889
5.513
10.0
161.790
70.277
29.423
17.983
13.081
10.513
8.995
8.023
7.361
6.891
IEEE Moderately Inverse
0.5
3.220
1.902
1.216
0.973
0.844
0.763
0.706
0.663
0.630
0.603
1.0
6.439
3.803
2.432
1.946
1.688
1.526
1.412
1.327
1.260
1.207
2.0
12.878
7.606
4.864
3.892
3.377
3.051
2.823
2.653
2.521
2.414
4.0
25.756
15.213
9.729
7.783
6.753
6.102
5.647
5.307
5.041
4.827
6.0
38.634
22.819
14.593
11.675
10.130
9.153
8.470
7.960
7.562
7.241
8.0
51.512
30.426
19.458
15.567
13.507
12.204
11.294
10.614
10.083
9.654