2 Functions
378
7SD5 Manual
C53000-G1176-C169-1
2.22 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.
2.22.1 Measurement Supervision
2.22.1.1 Hardware Monitoring Functions
The device is monitored from the measuring inputs up to the command relays. Moni-
toring checks the hardware for malfunctions and disallowed conditions.
Auxiliary and
Reference Voltages
The processor voltage of 5 V is monitored by the hardware, and if the voltage decreas-
es below the minimum value, the processor is no longer operative. If it falls below the
minimum value, the device will be put out of service. When the normal voltage returns,
the processor system is restarted.
Failure of or switching off the supply voltage puts the device out of operation and a
message is immediately generated by a normally closed contact. Brief voltage inter-
ruptions of up to 50 ms do not disturb the operational readiness of the device (see for
the Technical Data).
The processor monitors the offset and reference voltage of the ADC (analog-digital
converter). The protection is suspended if the voltages deviate outside an allowable
range, and lengthy deviations are reported.
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. 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
from message buffers and fault record buffers, however, are kept stored.
Memory Modules
The main memory (RAM) is tested when the system starts up. If a malfunction occurs
then, the starting sequence is interrupted, the error LED and LED 1 flash while the
other LEDs blink at the same intervals. During operation, the memory is checked using
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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