Monitoring Functions; Method Of Operation; Hardware Monitoring - Siemens siprotec 7SA6 User Manual

6.19

Monitoring Functions

6.19.1 Method of Operation

6.19.1.1 Hardware Monitoring

Auxiliary and
Reference Voltages
Buffer Battery
Memory Modules
Sampling
Frequency
7SA6 Manual
C53000-G1176-C133-1
The device incorporates extensive monitoring functions of both the device hardware
and software; the measured values are also continually checked to ensure their
plausibility; the current and voltage transformer secondary circuits are thereby
substantially covered by the monitoring function. Furthermore it is possible to
implement a trip circuit supervision function by means of the available binary inputs.
The device is monitored from the measuring inputs up to the command relays.
Monitoring circuits and the processor check the hardware for faults and inadmissible
states.
The 5 V processor voltage is monitored by the hardware, as the processor would no
longer function once the voltage is below the minimum value threshold. The device is
taken out of service. On recovery of the voltage the processor system is restarted.
If the auxiliary supply fails or is switched off, the device is taken out of service; this
state is alarmed by a normally closed contact (can be changed to a normally open
contact via jumper, refer to subsection 8.1.3) Short dips in the auxiliary supply voltage
do not affect the serviceability of the device (refer to Sub-section 10.1.2 in the
technical data).
The processor monitors the offset and reference voltage of the ADC (analogue-to-
digital converter). In the case of inadmissible deviations, the protection is blocked;
permanent faults are alarmed.
The charging state of the internal battery buffer, which ensures the correct function of
the internal clock and the storage of counters and alarms in the event of auxiliary
supply failure is cyclically checked. If the voltage drops below the minimum
permissible level, the alarm ")DLO %DWWHU\" is issued.
The working memory (RAM) is tested during booting of the system. If a fault is
detected, the booting sequence is terminated and a LED blinks. 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 (EEPROM) is cyclically generated and
compared with the checksum which is computed after each change of the stored
parameters.
If a fault is detected, the processor system is restarted.
The sampling frequency and the synchronism of the internal buffer modules is
continuously monitored. If deviations occur which cannot be removed by re-
synchronization, the processor system is rebooted.
Functions
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