Supervision; Hardware Monitoring; Software Monitoring - Siemens SIPROTEC 4 7VE61 Manual

Functions

2.12 Supervision

2.12 Supervision
The device incorporates comprehensive monitoring functions which cover both hardware and software; the
measured values are continuously checked for plausibility, so that the voltage transformer circuits are also
included in the monitoring system to a large extent.Special monitoring functions are integrated, in particular
for the synchronizing function.
2.12.1

Hardware Monitoring

The device monitoring extends from the measuring inputs to the binary outputs. Monitoring circuits and
processor check the hardware for malfunctions and inadmissible conditions.
Auxiliary and Reference Voltages
The processor voltage of 5 VDC is monitored by the hardware since if it goes below the minimum value, the
processor is no longer functional. In that case the device is put out of operation. When the normal voltage
returns, the processor system is restarted.
Failure or switching off the supply voltage removes the device from operation and a message is immediately
generated by the "life contact" (an alternatively NO or NC contact). Brief auxiliary voltage interruptions of less
than 50 ms do not disturb the operational readiness of the device (for nominal auxiliary voltage ≥ DC 110 V).
The processor monitors the reference voltage of the ADC (analog-to-digital converter). In case of inadmissible
deviations the protection is blocked; persistent faults are signalled (indication:
Buffer Battery
The buffer battery, which ensures operation of the internal clock and storage of counters and messages if the
auxiliary voltage fails, is periodically checked for charge status. If it is less than an allowed minimum voltage,
then the Fail Battery indication is issued.
If the device is isolated from the auxiliary voltage for several hours, the internal back-up battery is switched off
automatically, i.e. the time is not registered any more. Messages and fault recordings however are kept
stored.
Memory Components
All working memories (RAMs) are checked during start-up. If a fault occurs in this process, the start is aborted
and an LED starts flashing. During operation the memories are checked by means of their checksum.
For the program memory (EPROM), the cross-check sum is cyclically generated and compared to a stored
reference program cross-check sum.
For the settings memory, the cross-check sum is formed cyclically and compared to the cross-check sum that is
freshly generated each time a setting process takes place.
If a fault occurs the processor system is restarted.
Probing
The sampling frequency and the synchronism between the internal buffer modules is continuously monitored.
If any deviations cannot be removed by renewed synchronisation, then the processor system is restarted.

Software Monitoring

2.12.2
Watchdog
For continuous monitoring of the program sequences, a watchdog timer is provided in the hardware (hard-
ware watchdog) which will reset and completely restart the processor system in the event of processor failure
or if a program falls out of step.
A further software watchdog ensures that any error in the processing of the programs will be recognized. This
also initiates a restart of the processor system.
112
Error A/D-conv. ).
SIPROTEC 4, 7VE61 and 7VE63, Manual
C53000-G1176-C163-3, Edition 10.2017