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required in order to load a custom curve. Time-to-trip has a
0.00
range of
to
seconds in steps of
655.35
i
p
1 . 1
20. 00
li
has a range of
to
point in the data set must be ilip
20.
ilip
Points in between these two limits can be for any
=
values of 1/lp and t as long as the slope (t:.T/{tlilip)) of the
curve described by the points is between
- = (vertical). For input current in excess of
will enter a definite time mode and the curve will be consid
ered to be flat (constant time) at the time value associated
ilip
20.
with
=
Once loaded, a custom curve is not adjust
able since there is no time dial adjustment.
A.S
Overvoltage Equations
The ISGS relay provides a moderately inverse overvoltage
characteristic that is defined by the following equation:
v
::;
::;
1 .0 1
if
1 .5
For
p
T =
v
if > 1 .5
For
p
A D
T =
+ BD
( 1 .5 )
1
Where:
T
=time to trip, in seconds
v
=
measured input voltage
vp
pickup value ("tap setting")
=
v
v
= multiple of pickup setting
P
0
0. 1
= time dial setting,
to 9.9 in steps of
and
A, 8,
N
= constants which, for the moderately inverse
curve, are:
A = 0.51
8 = -0.45
N = 0.5
38
0.01
seconds.
0.01 .
in steps of
The first
1
1
the last point must be
=
.
,
0
(horizontal) and
i
o
20
p
x
the relay
0. 1
A.6
Undervoltage Equations
The ISGS relay provides aa moderately inverse undervoltage
characteristic that is defined by the following equation:
v
::;
::;
0.5
if
0.99
For
p
T =
v
if < 0.5
For
p
AD
T =
+ BD
N -
( 1 .5 )
1
Where:
T =time to trip, in seconds
v
measured input voltage
=
vp
pickup value ("tap setting")
=
v
v
= multiple of pickup setting
P
0
0. 1
time dial setting,
to 9. 9 in steps of
=
and N
A, B,
constants which, for the moderately inverse
=
curve, are:
A = 0.51
8
=
-0.45
N = 0
.
5
A.7
Time-Current Characteristic
Curves
The standard time-current characteristic curves are shown
in Figure A.1 through Figure A.9.
A.8
Time-Voltage Characteristic
Curves
The standard time-voltage characteristic curves are shown
0
1 1 .
in Figure A.1
and Figure A.
Siemens Energy
0. 1
&
Automation, Inc.
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