176 The PQF-Manager user interface
Manual Power Quality Filter PQFM
current. In
the filter measures also the capacitor bank current. While
in the case of
the SDP will also work, it will be slightly less efficient
since the influence of the capacitors will be spread over a much wider
frequency bandwidth. Harmonic filtering in the affected bandwidth may be
interrupted more often for parameter optimization, this leading to a less
optimal filtering performance.
•
Ensure that the filter is in Mode 3.
−
In installations where detuned banks are present, it is recommended not to select
harmonic orders below the tuning frequency of the detuned banks.
indicates the harmonics recommended to be deselected for different types of
detuned banks.
Table 58: Recommended harmonics to be deselected for different detuned bank types
Detuned bank type
Harmonics recommended to be deselected
5.67 %
2, 3, 4
6 %
2, 3, 4
7 %
2, 3
14 %
2
For other types of detuned bank please contact your ABB Service provider to
evaluate the resonance frequency and the harmonics that are recommended to
be deselected.
When background distortion is present on the network and detuned capacitor
banks are installed adjacent to the active filter but connected downstream of
the filter CTs, filter resources will be lost. To overcome this, it is recommended
to either connect the detuned capacitor bank upstream of the filter CTs or to
use the CT connection approach shown in
Feeding
transformer Filter CTs
Detuned
capacitor
bank
PQFx
+
-
Figure 99: Connection approach for installations where detuned capacitor banks are installed
adjacent to the active filter but downstream to the active filter CTs (background distortion
present)
−
In installations where active filters and passive filters are present, the active
filters must be installed downstream of the passive filter. If this is not possible,
the CT connection scheme of
shall be used.
