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Effective 10/2004
Page 25
I.L. 70C1036H05
Figure 4.5 Instantaneous Current Settings
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 3.4, Zone Interlocking.
In addition to standard Ground Fault protection, the Digitrip
1150 Trip Unit also has a GROUND FAULT MEMORY
function which 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 sputtering 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.
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,
an associated time delay is adjustable from 0 to 240
seconds with initial factory default of 10 seconds. The
setting time tolerance is +/- 3% or +/- 0.3s (whichever is
greater). A difference between Max phase and Min phase
higher than the Amp Unbalance % settings will cause the
breaker to trip with an AMPERES OUT OF BALANCE
message and red Trip LED illuminated in the right corner of
the Digitrip front panel.
This function does require
external auxiliary power to the Digitrip unit.
To avoid
unnecessary operation of this function the circuit breaker
must be carrying 55% of the
I
r rating on at least one phase
before it will trip via Amp Unbalance.
M1
Inst.
x n
I
6
Available Settings
2, 2.5, 3, ...
9, 9.5, 10...
In Multiples of
Rating Plug
Amperes ( n)
I
Max setting possible is specified on rating plug
.
9, 9.5, 10, 10.5, 11, 11.5, 12, OFF
9, 9.5, 10, 10.5, 11, 11.5, 12, 12.5, 13,
13.5, 14, OFF
or
Available Settings
.24, ... 1.0
Gnd PU
Setting
x n
I
.4
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 I T GROUND SLOPE
2
Gnd. Time
.3 Sec.