2 Functions
168
7UM61 Manual
C53000-G1176-C127-3
Note
Voltage sum monitoring is only effective if an external displacement voltage is con-
nected at the displacement voltage measuring input and this is also notified via the pa-
rameter
223
UE CONNECTION
to the device.
Voltage sum monitoring can operate properly only if the adaptation factor
Uph /
Udelta
at address
225
has been correctly configured (see Section 2.3.1).
Figure 2-63
Voltage Sum Monitoring
Software Monitorings
Watchdog
For continuous monitoring of the program sequences, a time monitor is provided in the
hardware (hardware watchdog) that expires upon failure of the processor or an inter-
nal program, and causes a reset of the processor system with complete restart.
An additional software watchdog ensures that malfunctions during the processing of
programs are discovered. This also initiates a restart of the processor system.
To the extent such a malfunction is not cleared by the restart, an additional restart
attempt is begun. After three unsuccessful restarts within a 30 second window of time,
the device automatically removes itself from service and the red ”Fault" LED lights up.
The operational readiness relay ("Life contact") opens and issues an indication (alter-
natively as NO or NC contact).
Monitoring External Transformer Circuits
Interruptions or short circuits in the secondary circuits of the current and voltage trans-
formers, as well as faults in the connections (important for commissioning!), are de-
tected and reported by the device. The measured quantities are cyclically checked in
the background for this purpose, as long as no system fault is present.
Current Symmetry
During normal system operation a certain degree of symmetry of the currents is ex-
pected. The symmetry is monitored in the device by magnitude comparison. The
smallest phase current is compared to the largest phase current. Asymmetry is recog-
nised if
| I
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BAL. FACTOR I
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BALANCE I LIMIT
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