ABB PQFS Installation, Operation And Maintenance Instructions page 187

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A critical fault is a fault that after occurrence cannot be successfully
automatically cleared by the system within a reasonable time. The time frame
considered depends on the error type. If the fault is considered critical by the
system, the label 'Critical' will be shown in the event logging window. In
addition, the PQF item in the PQF-Manager 'Welcome' screen will display the
label 'ACK. FAULT. Note however that if the fault disappears fast, this label
disappears too.
Depending on the type of critical fault and the number of occurrences, the filter, when
running, may either:
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Stop (open the main contactor) and await user intervention. In this condition
the alarm contact of the PQF-Manager will switch on after a programmable
delay and the 'Armed' indicator will be OFF. The user has to acknowledge the
fault (with the PQF-Manager via Modbus or via remote control) before the filter
can be restarted.
By default, the 'Armed' indicator is associated with the fourth digital output
contact (cf. Table 9
top of the PQF-Manager display (Cf.
status of the digital output. Alternatively, the digital output considered can be
wired to monitor the 'Armed' indicator by distance (cf.
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Stop (open the main contactor) and restart automatically if the fault
disappears. In this condition the alarm contact of the PQF-Manager will switch
on after a programmable delay and the 'Armed' indicator will be ON. If it takes
a long time before the fault disappears, the user may decide to give a filter
stop command. This is done by highlighting the 'PQF ACK. FAULT' item in the
'Welcome' menu and selecting
be OFF.
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Stop briefly without opening the main contactor and continue filtering when
the error has disappeared. This is essentially the same case as the one
described above but the error phenomenon disappears faster than the time
required to generate a main contactor opening command.
If the filter is OFF and a critical error occurs (e.g. network undervoltage), the errors
will also be reported in the event log. As long as a critical fault condition exists (e.g.
permanent undervoltage on one phase) the display will show the message 'ACK.
FAULT' and the filter will refuse to start. The 'Armed' indicator on the PQF-Manager
will be OFF.
When pressing 'ACK. FAULT' the filter will display a message relevant to the problem.
It also shows a list of the most recent critical faults that have been recorded.
If the filter is in remote control operation and the message 'ACK. FAULT' is present on
the PQF-Manager, the fault can be acknowledged by sending a 'STOP' command by
remote control (low signal). Alternatively, the remote control functionality can be
and Table 10). The digital output contact monitor at the
Figure 51
. After this, the 'Armed' indicator (a) will
Manual Power Quality Filter PQFS  Troubleshooting guide 187
item 3) can be used to check the
Section 6.12.4)