Monitoring Functions; Method Of Operation; Hardware-Monitoring - Siemens siprotec 7SA522 User Manual

Functions
6.16

Monitoring Functions

6.16.1 Method of Operation

6.16.1.1 Hardware–Monitoring
Auxiliary and Refer-
ence Voltages
Buffer Battery
Memory Modules
Sampling
Frequency
6-216
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. 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. Moni-
toring 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 con-
tact 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 A/D (analogue-to-dig-
ital converter). In the case of inadmissible deviations, the protection is blocked; per-
manent 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 sup-
ply failure is cyclically checked. If the voltage drops below the minimum permissible
level, the alarm "%DWWHU\ HPSW\" is issued.
The working memory (RAM) is tested during booting of the system. If a fault is detect-
ed, the booting sequence is terminated and a LED blinks. During operation the mem-
ory 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 com-
pared with the checksum which is computed after each change of the stored parame-
ters.
If a fault is detected, the processor system is restarted.
The sampling frequency and the synchronism of the internal buffer modules is contin-
uously monitored. If deviations occur which cannot be removed by re-synchronization,
the processor system is rebooted.
7SA522 Manual
C53000-G1176-C119-2