Switching Onto A 3-Phase Measuring-Voltage Failure, Low Load - Siemens 6MD85 Manual

Supervision Functions
8.3 Supervision of the Secondary System
current of phase currents is formed from the difference between the present current phasor and the current
phasor of the previous period. This allows to take into account a jump of the current phase.
8.3.2.5

Switching onto a 3-Phase Measuring-Voltage Failure, Low Load

Logic
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Figure 8-8
Switching onto a 3-phase measuring-voltage failure is detected if the following criteria are fulfilled simultane-
ously:
•
All 3 phase-to-ground voltages have dropped below the threshold value 3ph.fail. - VA,VB,VC <.
•
The circuit breaker is detected to be in closed position. The detection takes place either via the phase
currents or via the ≥1-pole closed signal, which is generated via the circuit-breaker auxiliary contacts.
You can find more detailed information in chapter
Object.
A voltage jump – such as in a 3-phase measuring-voltage failure with closed circuit breaker (see
chapter8.3.2.4 3-Phase Measuring-Voltage Failure
measuring-voltage failure. If the monitoring is not blocked, the time delay SO 3ph.fail. - time delay
is started. After the time has elapsed, the indication SO 3ph.failure-alarm is displayed. A dropout of the
monitoring is only possible by a recovery of the voltage.
The supervision is blocked as soon as a pickup of a protection function is detected within a protection function
group and the time delay of the supervision has not yet elapsed.
This subfunction also covers the situation of a low load with 3-phase measuring-voltage failure and closed
circuit breaker, because the circuit-breaker condition is also determined from the circuit-breaker auxiliary
942
Logic Diagram Switching to 3-Phase Measuring-Voltage Failure
5.8.6 Circuit-Breaker Condition for the Protected
) – does not occur in the case of switching to a 3-phase
SIPROTEC 5, High-Voltage Bay Controller, Manual
C53000-G5040-C015-9, Edition 11.2017