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lnstallation and
Adjustments lnstructions
Ground
Fault
DelaY
il,"
gtornO fauli
delay
sets the
tripping
delay
of the
trip
unit
in
i""pin." 6
igr.orno
current in excess of the ground fault
pi"[rp i"u"f
tfrE
ground fault delay band
is
an
inverse
l2t
ramp
iunction
that reveits to
a
fixed
delay
at
the value selected with
if'," gt;unO fault
delay switch. The lower value
of
the
l'?t
delay
Ouni
"
presei to a value
of
.5
seconds at a ground
current
"orr"tp,jnJing
to
t.S times the ground fault
pickup
The fixed
delay may
belet
to
10,
25,
or
.40
seconds'
Example
-
Ground Fault
DelaY
Bands
Ground Fault
MemorY
Circuit
ALt
Static
Trip lll trip
units
with ground fault protection
come
equipped with
a
ground
fault
memory
circuit
This
circuit
efieitivety
integraies ground fault
currents
with
time
This
p;;;".;.
adled
pro-tection
by preventing
the
ground
fault
delay circuits from
being
reset
when the ground fault currents
u[-ini"tritt"nt
and/or erratic. The time
constants
for
the
current
integration are preset within the
trip
unit as
a
function
of
the ground fault
delaY.
Constructing
a
Time'Current
Curve
in"
toLfo*indinstructions
are
for
constructing
a
Time-Current
Curve for
atrip
unitwith
long time,
shorttime, and instantaneous
Lutt
protection,
The
conslruction of a curve for ground
fault
pr-otection or
for
trip
units without short time
or
without instan-
ianeous fault protection
is
very similar'
i.
Setect
the
long time
setting and delay band to be
used'
Example:
.6 long time setting
'1O-second
delaY band
2.
Select
the
short
time
PickuP
Example:
4 times
the
long
time
setting
lc)
3.
Lightly
trace a
line
from the long time pickup point
to the
-
[i"r#""
point given
in
the
table
below for the selected
L""g
T*"
O"tay"aanO
Now darken
the
line between the
L"g"ti;"
ptku6
point and the
intersection with
the
mini-
,ril
if-,oti time
pickup
line;
extending
the
trace'
if
neces-
tuiy
ttf-,it
ini"rsection
defines the shori time
pickup
point)
if-li6
fln" i.
tf,"
lower
limit
of
the long
time delay
band
(Note:
*itf',orisf,ott
time
fault
protection
the
line
would
extend to
the
instantaneous PickuP Point
)
L-;pl;
-
ito,
(1,
3b0 sec)
to
short
time pickup
point
(The line
would
Pass
through
the
reference
Point
(6x,
10
sec)
)
Lono
Time
Long
Time
Reference
Dela]r
Band
PickuP
Point
l^oinl
5o
t,j"onot
(1x
1O8O
sec)
(6x'
30 sec)
i;;;;4.
(tx, otz
sec)
(6x
17
sec)
ro
seconOs
(tx,
gOo
sec)
(6x'
10
sec)
o
r""".0.
(tx
zto
secl
(6x, 6 sec)
5.s
s"conot
(tx, tzo
sec)
(6x,3
5 sec)
4.
Drawavertical
linefrom
thetop
of
the
graphtothe longtime
pi"frp
[oint.
This line defines
the
minimum
long
time
pickup.
Erur'pf",
From
(1x,
1OO0O
sec)to
(1x'
360 sec)
Select
the
short time
delay band to
be
used'
Example:
,3-second delaY band
Draw
a
vertical
line
from the short time
pickup
point
on
the
[ng
t-"
J"f
iy
line
to
the
selected
short
time
delay
This
tlne"defines the minimum short
time pickup'
Example:
From
the
short
time pickup
point to
.3-second
time
line
Select
the
instantaneous PickuP'
Example:
12
times
current
sensor rating
Since the instantaneous
pickup
is
selected with respect to
if-l"irit"nt
t"nsor
rating,
it
must
be
divided bythe
long
time
pl"t
rp
to determine
its position on
the graph'
ExamPle:
12
+
.6
=
20
6.
8.
Draw a horizontal line along the short time
delay
line from
-
the short
time
picku
p line
to
ihe
instantaneous
picku
p
point'
ihi,
tin"
is
the
lower limit of
the
short
time delay band'
f*umpfe'
From 4
to
20 along
the
3-second
time
line
9.
Draw
a
vertical
line
from the instantaneous
pickup
point to
-
th;
bottom
of the
graph
This
line defines
the
minimum
instantaneous
PickuP.
ir*pll,
From
(2bx.
.3
sec)to
(2Ox'
01 sec)
10.
The
maximum
lines
of
the long
time
pickup'
long time delay
"
O""J
u.O
short
time
plckufare
offset from
the
minimum
[nbt
OV
20%.fhe
maximum line of the short time
delay
bu;;
id .07
seconds
greater than
the delay setting'
Draw
these
lines,
i;pi"'
a
Maximum long
time pickup.is
a
vertical
line
trom
(1
.2x, 10b00 sec)
to
(1
2x
360 sec)
b.
Maximum long time delay
is
from (1
2x'
360
sec)
to
maxiftum
short
time pickup
(4
x
120"k
=
4.8).
The
line
would pass
through
the new
ref
eience
point
(6
x 120%
=7
2x'
10
sec)
c
Maximum short time
pickup
is a
vertical
line
f
rom
the
pickup
point
to
the
37-second time
line.
10
Ground Current in
Percent
of Ground Sensor
Rating
100
1
000
10
o
E
E
o
o
6)
a
,E
o
E
F
ba
np
i
l
I
nd
ck
l
llr
_H+l
fl-,1T'nn
I lll
lrl
llll'tDelayband,
{Hf,g?iffm
oicxT
11D
mini
elay
mur
-l
Tt
rl
,\
I
.4
seconc
-delay
bal9
..25
seconc
delay
banc
lll,ll
r';'.:l],:,:',r
:"
r'
'1*l*1'r
it
1r
t
-.1
seconc
delay
banc
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