32
SEL-FT50/SEL-FR12 Fault Transmitter and Receiver System
Instruction Manual
Date Code 20210405
Device Installation
➤
Use different Unit IDs for any SEL-FT50 trios that may experience
simultaneous through-fault current, even if those SEL-FT50 Fault
Transmitters are on different networks. See
Avoiding Radio Interfer-
ence From Adjacent Networks on page 24
for details.
Setting the Network ID
Configure your SEL-FT50 Fault Transmitters to communicate on the same net-
work as your SEL-FR12 by giving both devices the same Network ID. Devices
with different Network IDs cannot communicate.
Setting Fault Pickup
The topic of power system coordination is outside the scope of this guide. An
overcurrent element must supervise SEL-FT50 data when used in trip decisions
or other operations affecting protection. Choose an SEL-FT50 Fault Pickup to be
at or below the upstream protective device (e.g., recloser control) supervising the
overcurrent pickup setting (expressed in primary amperes).
Because the SEL-FT50 measurement accuracy is not as accurate as a relay, take
care when choosing your fault pickup settings. The measurement accuracy for
each trip threshold is spelled out in the specifications section. Follow the guide-
lines in the following table to ensure the right pickup levels while avoiding false
pickups.
Table 11
and
Table 12
provide the recommended pickup settings based on the
expected load and fault currents. These tables take into account the different
pickup specifications for each product family (two styles of CTs).
Table 11
Fault Pickup Accuracy Considerations for FT50-0001/FT50-0003/
FT50-0005/FT50-0006 (U.S.A., Canada, Peru, Australia, New Zealand, and
Brazil)
Fault Pickup Level
(rms)
Host Relay Pickup Setting
(rms)
Load Behind FT50
(rms)
50 A
> 60 A
< 40 A
100 A
> 120 A
< 85 A
200 A
> 240 A
< 170 A
400 A
> 480 A
< 360 A
600 A
> 720 A
< 540 A
800 A
> 960 A
< 720 A
1000 A
> 1200 A
< 900 A
1200 A
> 1440 A
< 1080 A
NOTE:
The SEL-FT50 current
measurement circuitry is not as
precise as a protective relay
overcurrent element. Refer to
Specifications on page 41
for fault
pickup accuracy, response
characteristics, and device ratings.
