5.2.6 Programming Problems
CAUTION
Incorrect parameter settings will not damage the active
filter but can have a very negative influence on the grid
and can potentially damage other equipment connected to
the grid.
Difficulty with active filter operation can be a result of
improper programming of the filter parameters. Three
areas where programming errors may effect the filter
performance are:
•
CT settings
•
References and limits
•
I/O configuration
Any references or limits set incorrectly will result in less
than optimal filter performance. For instance, if the
reference for the Cos Phi parameter is set too low, the unit
will be unable to reach full compensation of reactive
currents. Parameters must be set according to the
requirements of the particular installation. References are
set in the parameter group 300-0*.
Incorrectly set I/O configuration usually results in the filter
not responding to the function as commanded. It must be
remembered that for each control terminal input or
output, there are corresponding parameters settings. These
settings determine how the filter responds to an input
signal or the type of signal present at that output. Using
an I/O function must be thought of as a two step process.
The desired I/O terminal must be wired properly and the
corresponding parameter must be set accordingly. Control
terminals are programmed in the 5-0* and 6-0* parameter
groups.
5.3 Internal Active Filter Problems
The vast majority of problems related to failed filter power
components can be identified by performing a visual
inspection and the static tests as described in the test
section. There are, however, a number of possible
problems that must be diagnosed in a different manner.
The following discusses many of the most common
problems.
5.3.1 Overtemperature Faults
In the event that an overtemperature indication is
displayed, determine whether this condition actually exists
within the filter or whether the thermal sensor is defective.
Of course, this can easily be detected by feeling the
outside of the unit, if the overtemperature condition is still
present. If not, the temperature sensor must be checked.
This can be done with the use of an ohmmeter in
accordance with the thermal sensor test procedure.
5.3.2 Current Feedback Problems
CAUTION
Incorrect wiring or installation of current transformers will
not damage the active filter but can have a very negative
influence on the grid and can potentially damage other
equipment connected to the grid.
Providing suitable current feedback signals from
customer’s current transformers (CT) is very important for
the correct operation of the active filter. Most issues,
during active filter commissioning, are related to the
incorrect installation or wiring of customer’s current
transformers.
It is strongly recommended prior to commissioning the
active filter to perform a visual inspection of the CT instal-
lation and wiring as described in
. If the visual
proof is not possible, measure the CT's current feedback
signals on the current transformer input terminals with a
current probe rated for 1 A or 5 A, corresponding to the
secondary rating of the current transformers.
Monitoring the DC link voltage and the filter output
current on the LCP while operating the filter gives suitable
information about CT current feedback signals. The
indicated value of the DC link voltage should be nearly
constant, with variations less then 20 V.
Acoustic noise from LCL filter reactors can indicate
improper CT installation and operation of the active filter.
The noise should be fairly even, without crashes which
indicate instability of the active filter operation. Low
frequency noise oscillations usually indicate oscillations on
line power or in the load.
To ensure the proper operation of customer’s current
transformers, it is useful to monitor the waveform of the
current feedback signals. This can be done by using a
current probe, rated for 5A, and an oscilloscope. Measure
the current of the CTs and line current. The shape of the
signal should be the same with different values.
Active Filter and the Power...
VLT Advanced Active Filter AAF006 D and E Frames Service Manual
MG90Z122 - VLT
®
is a registered Danfoss trademark
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