Functions
2.42 Monitoring Functions
SIPROTEC, 7UM62, Manual
C53000-G1176-C149-7, Release date 03.2010
290
Additional Criteria
In addition to this, the function can either be blocked via a binary input or deactivated by an undervoltage pro-
tection at a separate voltage transformer set. If an undervoltage is also detected at a separate transformer set,
this is most probably not due to a transformer error and the monitoring switching can be blocked. The separate
undervoltage protection must be set non-delayed and should also evaluate the positive-phase sequence
system of the voltages (e.g. 7RW600).
Voltage at the U
E
Input
Depending on how U
E
is connected, it may be necessary to block the voltage measurement of this input. A
block can be generated with the CFC tool and combined with the indication „VT Fuse Failure“.
Other Blocks
Fuse failure monitores directly blocks functions (see Figure 2-135). If other functions, such as underexcitation
protection, need to be blocked, the indication „VT Fuse Failure“ must be used, and combined with the
protection fuction via the logic component (CFC).
Logic
When a fuse failure is detected (Figure 2-135 left-hand logic component), this status is stored. This ensures
that the fuse failure indication is maintained even in the event of a short circuit. As soon as the fuse failure has
been eliminated, and the positive sequence voltage has risen above 85 % of the nominal voltage, the stored
value is cancelled, and the fuse failure indication is reset with a delay of 10 s.
Figure 2-135 Logic Diagram of the Fuse-Failure-Monitor
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