Siemens SENTRON 3VL System Manual page 137

Parameter Setting buttons
I
N
I t
N
I
OFF
g g
1/.3
.6/.3
I 1/.1
N
.6/.1
100%
I t
G /
I t
g g
I
g g OFF
1/.3
.6/.3
I 1/.1
N
.6/.1
100%
Setting of the protection parameter for line and generator protection
The settings vary depending on the trip unit (ETU10, ETU12, ETU20, ETU22, LCD-ETU40
and LCD-ETU42). The following parameters can be set depending on the version:
L overload release I
The overload release I
takes place with the help of the left rotary encoding switch I
(example: IB = 250 A, In = 315 A => setting factor 250 / 315 = 0.79 corresponds to 0.8 on
the rotary encoding switch).
Delay time t
The delay time (or time-lag class) t
time is the tripping time at 6 x I
range, for example, when the rated current range scarcely differs.
S short-time delay short-circuit protection I
The short-time delay short-circuit protection can be set with regard to the tripping value of
the current I
and can be set between 1.5 to 10 x I
Delay time t
Depending on the requirements and on the trip unit, selectivity in the relevant circuit can be
achieved with appropriate selection of the delay time t
the "ON" range, this means the delay time is current-dependent. The I
For example, the higher the current, the faster the circuit breaker will trip (equivalent to the
overload release I
that is, constant. If the current reaches the set value I
time t
3VL molded-case circuit breakers
System Manual, 03/2009, 110 0110 - 02 DS 01
Effect on
characteristic curve
.6/.1
1/.1
.6/.3
1/.3
I
OFF N
50%
.6/.1
1/.1
.6/.3
1/.3
I
OFF
N
50%
:
R
is set to the operating current I
R
:
r
and the delay time t
sd
:
sd
). In contrast, the delay time in the "OFF" position is current-independent,
R
. The degree to which the current exceeds the value I
sd
Brief description
Tripping current of the
neutral conductor
protection I = 0.5 or 1
N
x I
R
Tripping current and
time delay of the
ground fault protection
I = Off, 1 or 0.6 x I
g
Off, 0.1 s or 0.3 s
can be set using another rotary encoding switch. The set
r
. In this way, selectivity can be achieved in the overload
r
:
sd
. I refers to the tripping value of the overload release I
sd sd
(depending on the circuit breaker).
R
sd
Parameter assignment/addressing
10.1 Setting the parameters
Reason
Monitoring of a possible overload
of a neutral conductor or
protection of a conductor with
reduced cross-section
Monitoring of a ground fault
t =
n g
of the circuit to be protected. This
B
that is set to the factor I
R
. If the rotary encoding switch is in
sd
t value is constant.
2
, the circuit breaker trips after the set
is not important.
sd
/I
B n
R
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