Siemens 3VA1 100 A, Руководство пользователя

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Description
2.6 Protection system
3VA molded case circuit breakers
Manual, 04/2015, A5E03603177010-02
77
2.6.5 Short-time delayed short-circuit protection (S)
The ID letter for short-time delayed short-circuit protection is "S" (stands for "Short-time
delay"). The S function of the trip unit can be used to implement time-selective short-circuit
tripping in low-voltage networks in which multiple molded case circuit breakers are installed
in series.
The short-time delayed short-circuit protection function protects phases L1 to L3 and the
neutral conductor. The protection function responds if the current in at least one phase
exceeds the set tripping current I
sd
for the set delay period t
sd
.
The S release operates according to a characteristic with a current-dependent curve I
2
t. The
electronic trip units ETU 5-series and 8-series can be optionally switched over to a current-
independent tripping characteristic.
2.6.6 Instantaneous short-circuit protection (I)
The ID letter for instantaneous short-circuit protection is "I" (stands for "Instantaneous").
This short-circuit protection function protects phases L1 to L3. The instantaneous short-
circuit protection function responds if the instantaneous value equal to the rms of the current
in at least one phase exceeds the instantaneous tripping current I
i
.
2.6.7 Ground-fault protection (G)
The ID letter for ground-fault protection is "G" (ground fault).
The G protection detects residual currents between phases and grounded, electrically
conductive parts. The ground-fault protection function responds if the ground fault current
exceeds the set tripping current I
g
for the set delay period t
g
.
Ground-fault protection can be implemented as a current-independent and a current-
dependent function (I
2
t).
On 4-pole molded case circuit breakers and 3-pole molded case circuit breakers with
external current transformer for N conductor, the G protection calculates the vector sum of
the currents of the three phases and the neutral conductor. The G release trips the breaker
or an alarm is issued via the communication system if the rms value of this vector sum
exceeds the set trip value I
g
for the duration of the set delay t
g
.