NOTE
Current sum monitoring can operate properly only when the ground current of the protected line is fed to
the fourth current measuring input (Ι
4
) of the device. TheΙ
4
transformer must have been configured with
parameter I4 transformer (address 220) as In prot. line.
[stromsummenueberwachung-020313-kn, 1, en_US]
Figure 2-64 Current sum monitoring
Software Monitoring
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 internal program, and causes a complete restart of
the processor system.
An additional software watchdog ensures that malfunctions during the processing of programs are discov-
ered. This also initiates a restart of the processor system.
If such a malfunction is not cleared by the restart, an additional restart attempt is begun. After three unsuc-
cessful 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 drops out and indicates „device malfunction“ with its normally
closed contact.
Offset Monitoring
This monitoring function checks all ring buffer data channels for corrupt offset replication of the analog/digital
transformers and the analog input paths using offset filters. Possible offset errors are detected using DC filters,
and the associated sampled values are corrected up to a specific limit. If this limit is exceeded, an indication is
generated (no. 191
Error Offset
) and integrated into the warning group indication (no. 160). As
increased offset values impair the measurements, we recommend sending the device to the OEM plant for
corrective action should this indication persist.
External Transformer Circuits
Interruptions or short circuits in the secondary circuits of the current and voltage transformers, as well as
faults in the connections (important for commissioning!), are detected and reported by the device. The meas-
ured quantities are periodically checked in the background for this purpose, as long as no system fault is
present.
2.14.1.2
2.14.1.3
Functions
2.14 Monitoring Functions
150 SIPROTEC 4, 7SD80, Manual
E50417-G1100-C474-A2, Edition 02.2018
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