Eaton 520 Operating Manual page 17

Operating Manual for Series NRX
Trip Units - Digitrip™ 520/520M
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 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 are:
g
I = (0.25/0.3/0.35/0.4/0.5/0.6/0.75/1.0) x I
g
There are two different ground fault curve shapes: fixed time (FLAT)
or I t response. The shape selected depends on the type of selective
2
coordination chosen. The I t response will provide a longer time delay
2
for current below 0.625 x I than will the FLAT response.
n
Available settings for the earth fault delay t
FLAT respNnsee: o = 0.1/ 0.2/ 0.3/ 0.4/ 0.5 s
g
I 2 o = 0.1/0.3/0.5
The I t response is applicable to currents less than 0.625 times the
2
ampere rating of the installed rating plug I
0.625 x I the I t response reverts to the FLAT response.
2
n
Turn rotary
switch to change
ground fault
current setting I
g
Figure 15. Applying GrNund Faulo Seooings
n
are:
g
. For currents greater than
n
Turn rotary
switch to change
ground fault time
setting t
g
g
Figure 16. GrNund Faulo Curreno Seooings
* On Label Indicates l
Figure 17. GrNund Faulo Time Seooings
Instruction Leaflet IL01301051E
effective September 2013
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
t (s)
g
Available Settings
0.1, 0.2, 0.3, 0.4, 0.5,
Seconds With
FLAT Response
l t Shape
2
Returns to FLAT
Response at
Approximately
0.625 l
n
0.1*, 0.3*, 0.5*
Seconds With
l
2 t Shape
2 t Shape.
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17