Schweitzer Engineering Laboratories SEL-751 - Table 4.10 Residual Overcurrent Settings; Table 4.11 Negative-Sequence Overcurrent Settings

4.15
Date Code 20170927 Instruction Manual SEL-751 Relay
Protection and Logic Functions
Group Settings (SET Command)
When a core-balance CT is connected to the relay IN input, as in Figure 2.28,
use the neutral overcurrent element to detect the ground faults. Calculate the
trip level settings based on the available ground fault current and the core-
balance CT ratio.
The relay offers four negative-sequence overcurrent elements to detect phase-
to-phase faults, phase reversal, single phasing, and unbalance load.
Table 4.10 Residual Overcurrent Settings
Setting Prompt Setting Range
Setting Name :=
Fac to ry Defa ult
RES OC TRIP LVL OFF, 0.25–100.00 A
a
0.05–20.00 A
b
a
For I
NOM
= 5 A.
b
For I
NOM
= 1 A.
50G1P := OFF
RES OC TRIP DLY OFF, 0.00–400.00 sec 50G1D := 0.50
RES OC TRQ CON SEL
OGIC 50G1TC := 1
RES OC TRIP LVL OFF, 0.25–100.00 A
a
0.05–20.00 A
b
50G2P := OFF
RES OC TRIP DLY OFF, 0.00–400.00 sec 50G2D := 0.50
RES OC TRQ CON SEL
OGIC 50G2TC := 1
RES OC TRIP LVL OFF, 0.25–100.00 A
a
0.05–20.00 A
b
50G3P := OFF
RES OC TRIP DLY OFF, 0.00–400.00 sec 50G3D := 0.50
RES OC TRQ CON SEL
OGIC 50G3TC := 1
RES OC TRIP LVL OFF, 0.25–100.00 A
a
0.05–20.00 A
b
50G4P := OFF
RES OC TRIP DLY OFF, 0.00–400.00 sec 50G4D := 0.50
RES OC TRQ CON SEL
OGIC 50G4TC := 1
Table 4.11 Negative-Sequence Overcurrent Settings
Setting Prompt Setting Range
Setting Name :=
Fac to ry Defa ult
NSEQ OC TRIP LVL OFF, 0.25–100.00 A
a
0.05–20.00 A
b
a
For I
NOM
= 5 A.
b
For I
NOM
= 1 A.
50Q1P := OFF
NSEQ OC TRIP DLY OFF, 0.0–400.0 sec 50Q1D := 0.2
NSEQ OC TRQ CON SEL
OGIC 50Q1TC := 1
NSEQ OC TRIP LVL OFF, 0.25–100.00 A
a
0.05–20.00 A
b
50Q2P := OFF
NSEQ OC TRIP DLY OFF, 0.0–400.0 sec 50Q2D := 0.2
NSEQ OC TRQ CON SEL
OGIC 50Q2TC := 1
NSEQ OC TRIP LVL OFF, 0.25–100.00 A
a
0.05–20.00 A
b
50Q3P := OFF
NSEQ OC TRIP DLY OFF, 0.0–400.0 sec 50Q3D := 0.2
NSEQ OC TRQ CON SEL
OGIC 50Q3TC := 1
NSEQ OC TRIP LVL OFF, 0.25–100.00 A
a
0.05–20.00 A
b
50Q4P := OFF
NSEQ OC TRIP DLY OFF, 0.0–400.0 sec 50Q4D := 0.2
NSEQ OC TRQ CON SEL
OGIC 50Q4TC := 1
NOTE: When a switch or breaker
closes, the three poles may not close
at the same time, creating a
momentary current unbalance
condition. To override this condition
use an overcurrent trip delay (for
example, 50GnD = 0.05 s).
NOTE: When a switch or breaker
closes, the three poles may not close
at the same time, creating a
momentary current unbalance
condition. To override this condition
use an overcurrent trip delay (for
example, 50QnD = 0.05 s).