
228
D90
PLUS
LINE DISTANCE PROTECTION SYSTEM – INSTRUCTION MANUAL
GROUPED PROTECTION ELEMENTS
CHAPTER 7: PROTECTION
IEC curves
For European applications, the D90
Plus
offers three standard curves defined in IEC 255-4
and British standard BS142. These are defined as IEC curves A, B, and C. The IEC curves are
derived by the operate and reset time equations.
Eq. 12
Eq. 13
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.
•
K
and
E
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 8: IEC (BS) inverse time curve constants
Table 9: IEC (BS) curve trip times (in seconds)
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
10.0
64.390
38.032
24.322
19.458
16.883
15.255
14.117
13.267
12.604
12.068
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
IEC curve shape
K
E
t
r
IEC curve A (BS142)
0.140
0.020
9.7
IEC curve B (BS142)
13.500
1.000
43.2
IEC curve C (BS142)
80.000
2.000
58.2
IEC short inverse
0.050
0.040
0.500
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
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
(
²
.
,
,
SLFNXS
7
RSHUDWH
7'0î
²
U
W
,
,
SLFNXS
7
UHVHW
7'0î