GE G60 Instruction Manual page 392

GROUPED ELEMENTS
Time overcurrent time calculations are made with an internal energy capacity memory variable. When this variable
indicates that the energy capacity has reached 100%, a time overcurrent element operates. If less than 100% energy
capacity is accumulated in this variable and the current falls below the dropout threshold of 97 to 98% of the pickup value,
the variable must be reduced. Two methods of this resetting operation are available: "Instantaneous" and "Timed." The
"Instantaneous" selection is intended for applications with other relays, such as most static relays, which set the energy
capacity directly to zero when the current falls below the reset threshold. The "Timed" selection can be used where the
relay must coordinate with electromechanical relays.
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.
where
T = operate time (in seconds)
TDM = Multiplier setting
I = input current
I = Pickup Current setting
pickup
A, B, p = constants defined in the table
T = reset time in seconds (assuming energy capacity is 100% and RESET is "Timed")
RESET
t = characteristic constant defined in the table
5
r
Table 5-29: IEEE inverse time curve constants
IEEE curve shape
IEEE Extremely Inverse
IEEE Very Inverse
IEEE Moderately Inverse
Table 5-30: IEEE curve trip times (in seconds)
Multiplier Current ( I / I
(TDM)
1.5
IEEE Extremely Inverse
0.5 11.341
1.0 22.682
2.0 45.363
4.0 90.727
6.0 136.090
8.0 181.454
10.0 226.817
IEEE Very Inverse
0.5 8.090
1.0 16.179
2.0 32.358
4.0 64.716
6.0 97.074
8.0 129.432
10.0 161.790
5-216
A B
28.2 0.1217
19.61 0.491
0.0515 0.1140
)
pickup
2.0 3.0 4.0
4.761 1.823 1.001
9.522 3.647 2.002
19.043 7.293 4.003
38.087 14.587 8.007
57.130 21.880 12.010
76.174 29.174 16.014
95.217 36.467 20.017
3.514 1.471 0.899
7.028 2.942 1.798
14.055 5.885 3.597
28.111 11.769 7.193
42.166 17.654 10.790
56.221 23.538 14.387
70.277 29.423 17.983
p t
r
2.0000 29.1
2.0000 21.6
0.02000 4.85
5.0 6.0 7.0
0.648 0.464 0.355
1.297 0.927 0.709
2.593 1.855 1.418
5.187 3.710 2.837
7.780 5.564 4.255
10.374 7.419 5.674
12.967 9.274 7.092
0.654 0.526 0.450
1.308 1.051 0.900
2.616 2.103 1.799
5.232 4.205 3.598
7.849 6.308 5.397
10.465 8.410 7.196
13.081 10.513 8.995
G60 GENERATOR PROTECTION SYSTEM – INSTRUCTION MANUAL
CHAPTER 5: SETTINGS
Eq. 5-9
8.0 9.0 10.0
0.285 0.237 0.203
0.569 0.474 0.407
1.139 0.948 0.813
2.277 1.897 1.626
3.416 2.845 2.439
4.555 3.794 3.252
5.693 4.742 4.065
0.401 0.368 0.345
0.802 0.736 0.689
1.605 1.472 1.378
3.209 2.945 2.756
4.814 4.417 4.134
6.418 5.889 5.513
8.023 7.361 6.891