Effective 11/2003
Page 22
I.L. 66A7535H02
Figure 4.5 Instantaneous Current Settings
4.2.1.8 GND PU Setting
The Ground Fault Current Settings are labeled with values
from .24 to 1.0x (
I
n) in 0.01 increments for Digitrip 1150V
style
(See Figure 4.6).
The Digitrip 1150V
i
style has an
Earth Pickup range of 0.10 to 1.0x (
I
n). External control
power is required to insure earth fault tripping for fault
currents and earth fault setting less than .24 per unit.
Available Settings
.24, ... 1.0
Gnd PU
Setting
x n
I
.4
Figure 4.6 Ground Fault Current Settings
4.2.1.9 GROUND TIME Setting
As illustrated in Figure 4.7, there are two different Ground
Fault Slopes: 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.
Nine Ground Time Settings for both FLAT and I
2
t re-
sponses for 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.
NOTE:
Also see Section 3.3, Zone Interlocking.
In addition to standard Ground Fault protection, the
GROUND FAULT MEMORY function serves to protect
loads in the event of a sputtering arc to ground. Without
this function, the trip unit resets each time the arc
sputters, and times out all over again, so that a sputtering
fault may not be detected. With the GROUND FAULT
MEMORY function, the trip unit “remembers” the sputter-
ing ground current for up to ten (10) times the Ground Fault
Time Setting. After that time, it resets automatically. The
GROUND FAULT MEMORY function resets quickly; on the
0.1 second setting, for example, the function will reset in
1.0 second.
I t SLOPE
Returns to FLAT
Response at
Approximately
0.625 n
2
I
Available Time Settings
.1, .15, .2, ... .4, .45, .5
Seconds with
FLAT or I2T GROUND SLOPE
Gnd. Time
.3 Sec.
Figure 4.7 Ground Fault Time Delay Settings
4.2.1.10 AMP UNBALANCE, PHASE LOSS
4.2.1.10.1 Amp Unbalance
The Amp Unbalance trip function can be selected in the
Program Settings - Program Curve menu
(See Appendix D-
12)
. It is set to OFF as a factory default. The pickup
unbalance is adjustable from 5% to 25%. Once selected,
* M1 Max setting possible is specified on rating plug.
INST PU
x n
I
6
Available Settings
2 to 12x steps of 0.5 and OFF,
2 to 14x steps of 0.5 and OFF
or *
In Multiples of
Rating Plug
Amperes ( n)
I
