17
Instruction Leaflet
IL01301051E
effective September 2013
Operating Manual for Series NRX
Trip Units - Digitrip™ 520/520M
EATON
www.eaton.com
GrNund faulo seooings
If the trip unit is equipped with earth fault protection, loads can be
protected against impermissibly high ground-fault currents. There is a
maximum of 1200A for UL type trip units (
Table 7
). The specific ground
current settings for each model are listed in
Table 6, Table 7
and
Table 8
and on the applicable time-current curve for the circuit breaker.
The response value I
g
together with the setting for the time delay t
g
determines the shut off of the ground fault. Available settings for the
ground fault pickup I
g
are:
I
g
= (0.25/0.3/0.35/0.4/0.5/0.6/0.75/1.0) x I
n
There are two different ground fault curve shapes: fixed time (FLAT)
or I
2
t response. The shape selected depends on the type of selective
coordination chosen. The I
2
t response will provide a longer time delay
for current below 0.625 x I
n
than will the FLAT response.
Available settings for the earth fault delay t
g
are:
FLAT respNnsee: o
g
= 0.1/ 0.2/ 0.3/ 0.4/ 0.5 s
I
2
o = 0.1/0.3/0.5
The I
2
t response is applicable to currents less than 0.625 times the
ampere rating of the installed rating plug I
n
. For currents greater than
0.625 x I
n
the I
2
t response reverts to the FLAT response.
Figure 15.
Turn rotary
switch to change
ground fault time
setting t
g
Turn rotary
switch to change
ground fault
current setting I
g
Applying GrNund Faulo Seooings
Figure 16.
I
g
Available Settings
0.25, 0.3, 0.35, 0.4,
0.5, 0.6, 0.75, 1.0
Specific Values Given
on Circuit Breaker
Time-Current Curve
and in
Table 4 Nr 5
GrNund Faulo Curreno Seooings
Figure 17.
t
g
(s)
Available Settings
0.1, 0.2, 0.3, 0.4, 0.5,
Seconds With
FLAT Response
l
2
t Shape
Returns to FLAT
Response at
Approximately
0.625
l
n
0.1*, 0.3*, 0.5*
Seconds With
l
2
t Shape
* On Label Indicates l
2
t Shape.
GrNund Faulo Time Seooings
