Siemens Sentron 3VA - Page 129

Applications
3.1 Use of the 3VA UL molded case circuit breakers in line protection
3VA molded case circuit breakers with UL and IEC certification
Manual, 01/2019, L1V30435333-01
127
Short-time delayed short circuit protection S:
•
I
sd
Adjustable from 0.6 to 9 / 10 x I
n
I
sd
= 40 A: In steps of 0.5 A
I
sd
≥ 100 A: In steps of 1 A
•
t
sd
Adjustable from 0.05 to 0.5 s
with a reference point of I
sd
= 8 x I
r
in steps of 0.01 s
The curve shape I
2
t = constant can be deactivated.
Instantaneous short-circuit protection I:
•
I
i
Adjustable from 1.5 to 9 / 10 / 12 x I
n
(dependent on rated operational current
and frame size)
In steps of 1 A
Ground-fault alarm (G):
The detection of the ground-fault current is based on a vectorial summation of the phase
currents and the neutral conductor current for 4-pole or 3-pole circuit breakers with external
current transformer for N conductor.
•
I
g
Adjustable from 0.2 / 0.4 to 1.0 x I
n
in absolute current values
In steps of 1 A
•
t
g
Adjustable from 0.05 to 0.8 s
with a reference point of 2 x I
g
In steps of 0.01 s
An alarm threshold I
gA
from 0.2 / 0.4 to 1 x I
n
can also be set. In steps of 1 A
The current-dependent curve shape I
2
t = constant can be deactivated.
If a ground fault is detected, the ETU556 or ETU856 only issues an alarm without tripping
the circuit breaker. This alarm is displayed directly on the LCD display and/or communicated
to higher-level systems via the communication connection, the EFB external function box
and the maintenance mode box.
Neutral conductor protection N:
The neutral conductor protection function is available only for 3-pole molded case circuit
breakers with external current transformer for N conductor for 4-pole molded case circuit
breakers.
•
I
N
Adjustable in steps of 1 A
3-pole
circuit breakers with external current transformer for N conductor:
I
n
= 40 A: 0.4 to 1.6 x I
n
I
n
≥ 100 A: 0.2 to 1.6 I
n
4-pole
circuit breakers:
I
n
= 40 A: 0.4 to 1.6 x I
n
I
n
≥ 100 A: 0.2 to 1.0 or 1.5 / 1.6 x I
n