ABB PQFS Installation, Operation And Maintenance Instructions page 207

Symptom
The filter is running
but it is unstable
(oscillating behavior).
The filter is running
with low load
indication and the
load harmonics are
not filtered.
Cause / State
There is a problem in the
CT connections or a
hardware problem.
Presence of (detuned)
power capacitor banks or
plain capacitors (LV or
MV).
The filter is installed on a
very weak network.
Two master units are fed
from the same CTs. The
setup guidelines for this
installation setup have
not been implemented.
The harmonics are not
selected, the curve
setting is very high or the
harmonics are put in
standby by the system.
The line currents
measured by the filter via
the CTs are lower than the
real load currents.
The filter is in standby-
mode, the IGBTs are not
switching.
Manual Power Quality Filter PQFS  Troubleshooting guide 207
What to do
−
Check the CT
installation (CT
location, CT shorts ...).
−
Check the connection
between the CT
terminal block X21 and
the main controller
terminals P5-1..P5-6.
−
Measure the line
currents (e.g. ammeter)
and compare them with
the line currents given
by the filter (PQF-
Manager or PQ-Link).
Refer to Section 8.10 for precautions
to take when plain capacitors are
present in the network.
−
Make sure that the filter
is operating in Mode 3.
−
If the problem persists,
contact your ABB
representative.
Interconnect the units with an RJ-45
cable. If this is not possible:
−
Select different
harmonics on both
filters.
−
If not possible, ensure
that one filter is
operating in Mode 1
and the other filter is
operating in Mode 3.
(Re)select the harmonics, check the
curve levels and ensure that the
correct settings are active
(Main/Auxiliary).
−
Check the CT cabling
for problems (CT-
installation, CT-shorts
...).
−
Check the CT settings
set up in the PQF-
Manager.
−
Check the standby
mode settings to
ensure that they