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Functions
2.24 Monitoring Functions
2.24
Monitoring Functions
The device is equipped with extensive monitoring capabilities - concerning both, hardware and software. In ad-
dition, the measured values are also constantly checked for plausibility, so that the current and voltage trans-
former circuits are largely integrated into the monitoring. It is also possible to implement trip circuit supervision.
This supervision is possible using appropriate available binary inputs.
2.24.1
Measurement Supervision
2.24.1.1 Hardware Monitoring
The device is monitored from the measuring inputs up to the command relays. Monitoring circuits and the pro-
cessor check the hardware for malfunctions and inadmissible conditions.
Auxiliary and Reference Voltages
The processor voltage is monitored by the hardware as the processor cannot operate if the voltage drops below
the minimum value. In that case, the device is not operational. On recovery of the voltage the processor system
is restarted.
If the supply voltage is removed or switched off, the device is taken out of service, and an indication is imme-
diately generated by a normally closed contact. Brief voltage interruptions of up to 50 ms do not disturb the
operational readiness of the device (see for the Technical Data).
The processor monitors the reference voltage of the ADC (analog-to-digital converter). The protection is sus-
pended if the voltages deviate outside an allowable range, and persistent deviations are reported.
Back-up Battery
The buffer battery, which ensures the operation of the internal clock and the storage of counters and indications
if the auxiliary voltage fails, is periodically checked for charge status. On its undershooting a minimum admis-
sible voltage, the indication „Fail Battery" (no. 177) is issued.
If the device is not supplied with auxiliary voltage for more than 1 or 2 days, the internal clock is switched off
automatically, i.e. the time is not registered any more. The data in the event and fault buffers, however, remain
stored.
Memory Components
The main memory (RAM) is tested when the system starts up. If a fault is detected during this process, the
startup is aborted. Error LED and LED 1 light up and the remaining LEDs start flashing simultaneously. During
operation the memory is checked by means of its checksum.
A checksum of the program memory (EPROM) is cyclically generated and compared with the stored program
checksum.
A checksum for the parameter memory (FLASH-EPROM) is cyclically generated and compared with the check-
sum which is computed after each change of the stored parameters.
If a malfunction occurs, the processor system is restarted.
418
SIPROTEC, 7SD5, Manual
C53000-G1176-C169-5, Release date 02.2011
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