Siemens siprotec 7SA6, Manual

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Functions
6-280
7SA6 Manual
C53000-G1176-C156-2
automatically removed. Definite time overcurrent emergency operation is possible
during the voltage failure if the overcurrent protection was configured accordingly (re-
fer to Section 6.11).
Additional
Measured Voltage
Failure Monitoring If no measuring voltage is available after power-on of the device (e.g. because the
voltage transformers are not connected), the absence of the voltage can be detected
and reported by an additional monitoring function. Where circuit breaker auxiliary con-
tacts are used, they should be used for monitoring as well. Figure 6-143 shows the
logic diagram of the measured voltage failure monitoring.
A failure of the measured voltage is detected if:
•
all three phase-to-earth voltages are smaller than
FFM U<max (3ph)
,
•
at least one phase current is greater than
PoleOpenCurrent
or at least one CB
pole is closed (selectable),
•
no protection function has picked up,
•
this condition persists for a settable time
T V-Supervision
(default setting:
3 sec).
This time T V-Supervision is required to prevent that a voltage failure is detected be-
fore the protection picks up.
If a failure is detected by anyone of these criteria, the annunciation
168
“
Fail U ab-
sent
” is output, and the device switches to emergency operation (see Section 6.11).
Figure 6-143 Logic diagram of the additional measured voltage failure monitoring
Emerg. Func.
Fail U absent
FNr 168
I
L1
I
L1
>
I
L2
I
L3
T 0
&
U
L3-E
I
L2
>
I
L3
>
U
L1-E
U
L2-E
Relay PICKUP
≥
1
&
≥
1
T V-Supervision
2916A
“1”
≥
1
&
U<
U<
U<
≥
1
V-Supervision
2915
off
with curr. supervis. ad CBaux
with curr. supervis.
FFM U<max (3ph)
2913A
PoleOpenCurrent
1130A
from CB position logic
(see Figure 6-151)
any pole closed