Measured Value Monitoring Functions
243
7UM62 Manual
C53000-G1176-C149-3
Figure 2-117 Voltage Sum Monitoring
2.38.1.2 Software Monitoring
Software
Monitoring
For continuous monitoring of the program sequences, a time monitor is provided in the
hardware (hardware watchdog) that runs upon failure of the processor or an internal
program, and causes a complete restart of the processor system.
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 ”Error” LED lights up.
The readiness relay opens and indicates ”device malfunction” with its normal contact.
2.38.1.3 Monitoring of External Current Transformer Circuits
Interruptions or short circuits in the secondary circuits of the current transformers or
voltage transformers, as well as faults in the connections (important for start-up!), are
detected and reported by the device. The measured quantities are periodically
checked in the background for this purpose, as long as no system fault is present.
Note:
Voltage sum (phase-earth) monitoring is only operative if an externally formed
displacement voltage s connected to the residual voltage input of the relay and if this
was communicated to the device via the parameter
Voltage sum (phase-earth) monitoring can operate properly only if the matching factor
at address
has been correctly configured (see Section 2.3.2).
U
F
U
N
U
max
U
N
SUM.thres.U
Slope:
SUM.Fact.U
