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lnstallation and
Adjustments lnstructions
Y
v
On
trip
units
with both ShortTime and Ground
Fault
Protection,
the ground fault
tripping
is
inhibited
if
the
trip
unit
is
executing
the short time
fault protection
sequence.
Ground
Fault Pickup
The ground
fault pickup
sets
the
level
of
ground current
at
which the
circuit
interruption sequence is
initiated. Together
with the
ground fault delay,
this
setting allows selective
tripping
between main
and feeder
or other
downstream circuit
break-
ers, The
ground fault pickup
may
be
set
to
20, 30, 40, 50
or,
60%
of
the
ground
sensor rating.
The
tolerance
on
the
ground
fault pickup
is plus
or minus
10%.
Note
that the ground fault pickup adjustment
references the
"Ground Sensor Rating."
This gives simple
referencing
re-
gardless of the
type of
ground fault scheme used.
Further-
more, it allows
trip
units
to
be lnterchanged between circuit
breaker frames
of
all
ratings and between different ground fault
schemes. The ground sensor rating appears on
the
circuit
breaker rating label above
the
trip
unit
for residual ground fault
sensing schemes, or on the right side of the
circuit
breaker
cubicle
for
direct source
or
zero sequence type schemes,
See
the ground
fault
sensing diagrams
for
additional
information.
Ground
Fault Protection
Ground
Fault
Frekup
Delay
50
SC
,10
,,1
^
:5
:n
30
)(\
',n
Grd
Serrsor
Direct Source or Zero Sequence Ground
Fault
Schemes
10
Ground Current in
Percent
of
Ground
Sensor Rating
EA
JU
100
10
50
o
!,
o
o
o
a
'.
E
tr
I
Ground fault
pickup
set
at
50%.
Pickup wi
I
be
between 45 and
Atro/-
nf
nrnr
rnrl
sensor
ratrng.
I
Example
-
Ground Fault
P
ckup
IY
Res
dua
Ground
Fault
Schemes
l5
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