Siemens SENTRON 3VL System Manual page 136

Parameter assignment/addressing
10.1 Setting the parameters
Parameter Setting buttons
I
L
R
I
1.0
R
.95
.9
.8
I
x
.7 .63
n
t
R
t
(S)
30
R
25
20
17
14
I
S
I
sd
10
sd
8
7
6
5
I t
2 t
sd
(S)
.4
sd
.3
.2
2
t I
.1
ON
.5
t
t
sd
(S)
.4
sd
.3
.2
2
t I
.1
ON
.5
I
I
i
I
11
i
10
8
6
I
x
5
n
136
Effect on
characteristic curve
.4
.45
.5
.6
2.5
4
6
8
10
1.5
2
2.5
3
I
x
4
R
0
.1
.2
I 2 t
.3
.4
OFF
0
.1
.2
I 2 t
.3
.4
OFF
1.25
1.5
2
3
4
Brief description
Tripping current of the
overload protection I =
R
0.4 to 1 x I
n
Delay (or time-lag
class) in the overload
range. The set time is
the tripping time at 6 x
I . t = 2.5 to 30s
R R
Tripping current of the
short-time delay short-
circuit protection I =
sd
1.5 to 10 x I
R
Switchover from a
constant time delay to a
I t characteristic curve
2
in the short-circuit
range I t = ON or OFF
2
sd
Delay time of the short-
circuit protection.
Please note: The
selection between t =
sd
constant and I t
2
characteristic t = 0 to
sd
0.5 s with the position
of the rotary encoding
switch
Tripping current of the
instantaneous short-
circuit release I = 1.25
i
to 11 x I
n
System Manual, 03/2009, 110 0110 - 02 DS 01
Reason
Limitation of the overload range
by setting to the operating current
of the circuit to be protected
Improved selectivity in the
overload range in switching
stations with several grade levels
when the rated currents differ
only slightly
Limitation of the short-circuit
range in which the current has to
be shut off faster than in the
overload range, but with a shorter
time delay to achieve time
selectivity to downstream
switchgear
Improved selectivity with
downstream switchgear, e.g.
LVHRC fuses
Improved selectivity of the short-
circuit protection in switching
stations with several grade levels
Limitation of the short-circuit
range in which the impermissibly
high current has to be switched
off as quickly as possible. This
also takes place for the self
protection of the circuit breaker
3VL molded-case circuit breakers