Schweitzer Engineering Laboratories SEL-751 - Table 4.9 Neutral Overcurrent Settings

4.13
Date Code 20170927 Instruction Manual SEL-751 Relay
Protection and Logic Functions
Group Settings (SET Command)
The relay offers two types of ground fault detecting overcurrent elements. The
neutral overcurrent elements (50N1T through 50N4T) operate with current
measured by the IN input. The residual (RES) overcurrent elements (50G1T
through 50G4T) operate with the current derived from the phase currents.
Table 4.9 Neutral Overcurrent Settings
Setting Prompt Setting Range
Setting Name :=
Fac to ry Defa ult
NEUT OC TRIP LVL OFF, 0.25–100.00 A
a
0.05–20.00 A
b
0.01–4.00 A
c
a
For I
NOM
= 5 A.
b
For I
NOM
= 1 A.
c
For I
NOM
= 0.2 A.
50N1P := OFF
NEUT OC TRIP DLY OFF, 0.00–400.00 sec 50N1D := 0.50
NEUT OC TRQ CON SEL
OGIC 50N1TC := 1
NEUT OC TRIP LVL OFF, 0.25–100.00 A
a
0.05–20.00 A
b
0.01–4.00 A
c
50N2P := OFF
NEUT OC TRIP DLY OFF, 0.00–400.00 sec 50N2D := 0.50
NEUT OC TRQ CON SEL
OGIC 50N2TC := 1
NEUT OC TRIP LVL OFF, 0.25–100.00 A
a
0.05–20.00 A
b
0.01–4.00 A
c
50N3P := OFF
NEUT OC TRIP DLY OFF, 0.00–400.00 sec 50N3D := 0.50
NEUT OC TRQ CON SEL
OGIC 50N3TC := 1
NEUT OC TRIP LVL OFF, 0.25–100.00 A
a
0.05–20.00 A
b
0.01–4.00 A
c
50N4P := OFF
NEUT OC TRIP DLY OFF, 0.00–400.00 sec 50N4D := 0.50
NEUT OC TRQ CON SEL
OGIC 50N4TC := 1
NOTE: If channel IN is rated 0.2 A
nominal, then it is recommended that
50NnD (n = 1–4) be set to at least a
minimum 2-cycle time delay.
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, 50NnD := 0.05 s).