4.26
SEL-751 Relay Instruction Manual Date Code 20170927
Protection and Logic Functions
Group Settings (SET Command)
Directional Control
for Neutral-Ground
and Residual-Ground
Overcurrent Elements
The directional control for overcurrent elements is enabled by making direc-
tional control enable setting EDIR. Setting EDIR and other directional control
settings are described in Directional Control Settings on page 4.53.
Six directional elements are available to control the neutral ground and resid-
ual ground overcurrent elements. Not all are available simultaneously. These
six directional elements are:
➤ Negative-sequence voltage-polarized directional element
➤ Zero-sequence voltage-polarized directional element
➤ Channel IN current-polarized directional element
➤ Zero-sequence voltage-polarized directional element (low-
impedance grounded system)
➤ Wattmetric and incremental conductance directional elements
(Petersen coil-grounded system)
➤ Zero-sequence voltage-polarized directional element
(ungrounded/high-impedance grounded system)
Figure 4.18 IEC Long-Time Inverse Curve: C4 Figure 4.19 IEC Short-Time Inverse Curve: C5
0.20
0.10
0.05
1.00
0.90
0.80
0.70
0.60
0.50
0.40
0.30
.7.6.5
.1
.9.8 1
.4
.2
.3
.5
.6
.8
.7
.9
1
2
3
4
5
7
6
423 765
10
98
40
20
30
70
50
60
80
90
100
50
9
8
10
20
30
40
300
200
100
80
60
70
90
1000
900
800
700
600
500
400
Time in Seconds
Multi
les of Picku
Time in Cycles 60 Hz (50Hz)
30 (25)
60 (50)
150 (125)
300 (250)
3000 (2500)
600 (500)
1500 (1250)
6000 (5000)
15000 (12500)
30000 (25000)
60000 (50000)
10
20
30
40
50
60
70
80
90
100
1
2
3
4
5
6
7
8
9
.1
.2
.3
.4
.5
.6
.7
.8
.9
.01
.02
.03
.04
.05
.06
.07
.08
.09
100
123456789.5 .6 .7 .8 .9
90
80
7
0
60
50
40
3
0
2
0
10
Time in Seconds
T
ime in Cy
cles 60 Hz (50 Hz
)
6000 (5000)
3000 (2500)
1500 (1250)
600 (500)
300 (250)
150 (125)
60 (50)
30 (25)
15 (12.5)
6 (5)
3 (2.5)
Multiples of Pickup
0.05
0.10
0.20
0.30
0.40
0.50
0.60
0.70
0.80
0.90
1.00
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