CHAPTER 7: PROTECTION
GROUPED PROTECTION ELEMENTS
D90
PLUS
LINE DISTANCE PROTECTION SYSTEM – INSTRUCTION MANUAL
227
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 method 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 by the operate and reset time equations.
Eq. 10
Eq. 11
The terms in the above equations are defined as follows.
•
T
operate
represents the operate time in seconds.
•
TDM represents the multiplier setting.
•
I
represents the input current.
•
I
pickup
represents the pickup current setting value.
•
A
,
B
, and
p
are constants and are defined in the table below.
•
T
reset
represents reset time in seconds, assuming the energy capacity is 100% and the
reset mode is timed.
•
t
r
represents the characteristic constant and is defined in the table below.
Table 13: IEEE inverse time curve constants
Table 7-1: IEEE curve trip times (in seconds)
IEEE curve shape
A
B
p
t
r
Extremely inverse
28.2
0.1217
2.0000
29.1
Very inverse
19.61
0.491
2.0000
21.6
Moderately inverse
0.0515
0.1140
0.020000
4.85
²
U
W
7'0î
UHVHW
7
,
,
SLFNXS
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
