Software Monitoring; Monitoring Of The Transformer Circuits - Siemens 7SC80 Manual

AD Transformer Monitoring
The digitized sampled values are being monitored in respect of their plausibility. If the result is not plausible,
message 181 Error A/D-conv. is issued. The protection is blocked, thus preventing unwanted operation.
Furthermore, a fault record is generated for recording of the internal fault.
2.12.1.3

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 (191
values impair the measurements, we recommend sending the device to the OEM plant for corrective action
should this indication persist.
2.12.1.4

Monitoring of the Transformer Circuits

Open circuits or short circuits in the secondary circuits of the current and voltage transformers, as well as
faults in the connections (important during commissioning!), 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.
Current Symmetry
During normal system operation, symmetry among the input currents is expected. The monitoring of the
measured values in the device checks this balance. The smallest phase current is compared to the largest
phase current. Asymmetry is detected if | Ιmin | / | Ιmax | < BAL. FACTOR I as long as Ιmax > BALANCE I
LIMIT is valid.
With Ιmax is the largest of the 3 phase currents and Ιmin the smallest. The balance factor BAL. FACTOR I
(address 8105) represents the permitted imbalance of the phase currents while the limit value BALANCE I
LIMIT (address 8104) is the lower limit of the operating range of this monitoring (see
parameters can be set. The dropout ratio is about 95 %.
This failure is therefore located below the curve for all values and is reported as
SIPROTEC Compact, 7SC80, Manual
E50417-G1140-C486-A8, Edition 07.2017
Error Offset ) and integrated into the warning group indication (160). As increased offset
Functions
2.12 Monitoring Functions
Figure 2-64). Both
Fail I balance .
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