2 Functions
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7SD610 Manual
C53000-G1176-C145-4
the voltage failure, provided that the differential protection is parameterized according-
ly (refer to Section 2.9).
Figure 2-85 Logic diagram of the 3-phase measured voltage failure monitoring
Additional Mea-
sured 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 2-86 shows the logic
diagram of the measured voltage failure monitoring. A failure of the measured voltage
is detected if the following conditions are met at the same time:
• All three phase-to-earth voltages are smaller than FFM U<max (3ph),
• At least one phase current is larger than PoleOpenCurrent or at least one
breaker pole is closed (can be set),
• No protection function has picked up,
• This condition persists for a settable time T V-Supervision (default setting: 3 s).
This time T V-Supervision is required to prevent that a voltage failure is detected
before the protection picks up.
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