REG 316*4 1MRB520049-Uen / Rev. C ABB Switzerland Ltd
6-3
6.4. Monitoring the hardware
For the most part, the hardware is either monitored or self-test-
ing both while the system is being initialised after switching on
and afterwards during normal operation. Upon switching on the
auxiliary supply, a test routine completely checks the hardware
including the RAM and the flash EPROM checksums. The func-
tion and accuracy of the A/D converter is tested by converting a
10 V reference voltage to a digital value and checking that the
result lies within ± 1%.
The switch-on test takes about 10 seconds while the green
(stand-by) LED does not light and the protection functions are
blocked. Upon successful completion of the test, the stand-by
LED flashes and the start-up routine commences. As soon as
the standby LED lights continuously, the device is operational.
The above routine continues to run as a background function
during normal operation, checking the memories (excepting the
RAM) at frequent intervals. The reference voltage is also
repeatedly converted together with the current and voltage
channels to monitor the A/D converters.
6.5. Diagnostic events
A corresponding entry is made in the event list whenever the
diagnostic function detects a failure.
The following entries in the list are possible:
· System start
The device was switched on.
· Protection restart
The protection and control functions were activated.
· System warm start
The device was restarted after the reset button was pressed
or a watchdog time-out.
· Protection stop
The protection and control functions were stopped by the
parameters being re-entered.
· Supply failure
The device was switched off or there was a supply failure.
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