Siemens SENTRON 3VL series - Page 120

Parameter assignment / addressing
9.1 Setting the parameters
3VL IEC molded case circuit breakers
120 System Manual, 11/2013, 110 0110 - 02 DS 03
Parameter
Setting buttons
Effect on
characteristic curve
Brief description
Cause
L
I
R
Tripping current of the
overload protection I
R
=
0.4 to 1 x I
n
Setting to the operating current of
the circuit to be protected
t
R
Delay (or time-lag
class) in the overload
range. The set time is
the tripping time at 6 x
I
R
. t
R
= 2.5 to 30 s
Improved selectivity in the
overload range in switchgear with
several grade levels when the
rated currents differ only slightly
S
I
sd
Tripping current of the
short-time delayed
short-circuit protection
I
sd
= 1.5 to 10 x I
R
Short-circuit release with time
delay. In this way, time selectivity
can be achieved with
downstream switching devices.
I
2
t
sd
Change from a
constant time delay to a
I
2
t characteristic curve
in the short-circuit
range I
2
t
sd
= ON or OFF
Improved selectivity with
downstream switchgear, e.g.
LVHRC fuses
t
sd
Delay time of the short-
circuit protection.
Please note: The
selection between t
sd
=
constant and I
2
t
characteristic t
sd
1)
= 0
to 0.5 s with the
position of the rotary
encoding switch
Improved selectivity of the short-
circuit protection in switchgear
with several grade levels
I
I
i
Tripping current of the
instantaneous short-
circuit release I
i
= 1.25
to 11 x I
n
Instantaneous short-circuit
tripping for immediate shutdown
of the molded case circuit
breaker when the permissible
short-circuit current is exceeded
N
I
N
Tripping current of the
neutral conductor
protection I
N
= 0.5 or 1
x I
R
Overload protection of a neutral
conductor or protection of a
conductor with reduced cross-
section