46
SEL-FT50/SEL-FR12 Fault Transmitter and Receiver System
Instruction Manual
Date Code 20210405
Appendix B: Two-Branch Application
Appendix B: Two-Branch Application
This application has two three-phase branches, A and B, as shown in
Figure 30
.
Branch B has a fuse and uses a fuse-blowing scheme, while Branch A does not.
When a fault occurs on Branch A, the recloser operates to clear the fault. In tradi-
tional protection schemes, those without the SEL-FT50/SEL-FR12 system, the
time-inverse overcurrent curves of the SEL-651R recloser control are set above
the fuse-clearing curve, resulting in longer tripping times for faults on Branch A.
Use the SEL-FT50/SEL-FR12 system to improve this protection scheme.
Insert a set of three SEL-FT50 Fault Transmitters on each branch, one per phase.
The SEL-FR12 connects to the SEL-651R with an SEL-C272 serial cable. In this
example, the load current of Branch A is 200 A, and the load current of Branch B
is 100 A. The 51 element pickup of the SEL-651R is set above 200 percent of the
load current. In this example, the fuse size is 140 T, the SEL-651R 51 element
pickup is 550 A, and the settings from
Table 16
apply.
D = switch is in the DOWN or OFF position.
U = switch is in the UP or ON position.
This settings example uses Network ID = 3, and the fault current pickup thresh-
old is set above the load current and below the pickup.
The Network ID of the SEL-FR12 matches the Network ID of the SEL-FT50
Fault Transmitters.
Table 17
assumes that the SEL-FT50 Fault Transmitters
require High Gain mode selections (see
Receive Signal Strength Indicator on
page 26
for details). See
Table 18
for the settings of the SEL-651R and
Table 19
for the SEL-651R transmit M
IRRORED
B
ITS
settings.
Figure 30
SEL-FT50/SEL-FR12 System Protection Scheme
R
SEL-FR12
SEL-651R-2
SEL-FT50
SEL-FT50
1
2
3
4
5
6
A
B
Table 16
Settings for the SEL-FT50 Fault Transmitters
SEL-FT50
Branch
Unit ID Control
(DIP) Switch
Positions
Network ID Control
(DIP) Switch
Positions
Pickup Threshold
Control (DIP)
Switch Positions
1
A
1—(DDDD)
3—(DDUD)
400 A—(DUU)
2
A
2—(DDDU)
3—(DDUD)
400 A—(DUU)
3
A
3—(DDUD)
3—(DDUD)
400 A—(DUU)
4
B
4—(DDUU)
3—(DDUD)
200 A—(DUD)
5
B
5—(DUDD)
3—(DDUD)
200 A—(DUD)
6
B
6—(DUDU)
3—(DDUD)
200 A—(DUD)
