2 Functions
198
7SD610 Manual
C53000-G1176-C145-4
2.15 Monitoring Functions
The device incorporates extensive monitoring functions of both the device hardware
and software; the measured values are also continually checked to ensure their plau-
sibility; the current and voltage transformer secondary circuits are thereby substantial-
ly covered by the monitoring function. It is also possible to implement trip circuit mon-
itoring, using appropriate binary inputs as available.
2.15.1 Measurement Supervision
2.15.1.1 Hardware Monitoring
The device is monitored from the measuring inputs up to the command relays. Mon-
itoring circuits and the processor check the hardware for faults and inadmissible
states.
Auxiliary and Refer-
ence 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 opera-
tional. 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 immediately generated by a normally closed contact. Brief voltage in-
terruptions 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 suspended 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 admissible 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 Compo-
nents
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 re-
maining 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 checksum which is computed after each change of the stored pa-
rameters.
If a malfunction occurs, the processor system is restarted.
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