4.174
SEL-751 Relay Instruction Manual Date Code 20170927
Protection and Logic Functions
Global Settings (SET G Command)
With these example settings, the relay enters daylight-saving time on the last
Sunday in March at 0200 h, and leave daylight-saving time on the third
Wednesday in October at 0300 h. The relay asserts Relay Word bit DST when
DST is active.
When you use an IRIG-B time source, the relay time follows the IRIG-B time,
including daylight-saving time start and end, as commanded by the time
source. If there is a discrepancy between the daylight-saving time settings and
the received IRIG-B signal, the relay follows the IRIG-B signal.
When using IEEE C37.118 compliant IRIG-B signals (e.g., Global setting
IRIGC := C37.118), the relay automatically populates the DST Relay Word
bit, regardless of the daylight-saving time settings.
When using regular IRIG-B signals (e.g., Global setting IRIGC := NONE),
the relay only populates the DST Relay Word bit of the daylight-saving time
settings are properly configured.
Simple Network Time Protocol (SNTP)
The SEL-751 Port 1 (Ethernet Port) supports the SNTP Client protocol. See
Section 7: Communications, Simple Network Time Protocol (SNTP) on
page 7.14 for a description and Table 7.5 for the settings.
Breaker Failure
Setting
The SEL-751 provides flexible breaker failure logic (see Figure 4.101). In the
default breaker failure logic, assertion of Relay Word bit TRIP starts the BFD
timer if any of the phase current remains greater than the 50BFP setting. If any
of the phase current remains greater than the threshold (50BFP) for BFD delay
setting, Relay Word bit BFT asserts. Use the BFT to operate an output relay to
trip appropriate backup breakers.
Table 4.72 Breaker Failure Setting
Setting Prompt Setting Range
Setting Name :=
Fac to ry Default
52A INTERLOCK Y, N 52ABF := N
CURRENT DETECTOR 0.10–10.00 A
a
a
Setting ranges and default Amp values shown are for 5 A nominal CT rating. Divide by 5 for
1A CTs.
50BFP:=0.1
BK FAILURE DELAY 0.00–2.00 sec BFD :=0.50
AUX TIMER DELAY Off, 0.01–2.00 sec ATD :=OFF
BK FAIL INITIATE SEL
OGIC BFI =:R_TRIG TRIP
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