72 Electrical design and installation
Manual Power Quality Filter PQFM
6.11.4 CT cable interconnection
WARNING: Failure to connect the CT’s to all units in a filter system in an appropriate
way will result in filter malfunctioning and possibly sever damage of the unit.
In a multi-unit PQFM-system, all units have to be supplied with the CT –measurement
results. In order to do this the CT’s have to be cabled to each unit in a daisy chain fashion.
The connection principle is shown in Figure
for the CT of phase which is fed to four
filter units. The same approach has to be implemented for the other phases too. A
maximum of 8 filter units can work in parallel in this fashion.
Figure 56: Principle of the CT interconnection circuit for multi-unit filters.
Note that the overall burden requirement for a complete filter system is 5 VA. To this
value has to be added the burden requirement of the interconnection cables to obtain
the total burden requirement of the CT’s to be used.
6.11.5 Connection of the power stage to the supply
As a final step in the interconnection process, the power stage of the new unit has to be
connected to the supply. When the filter has an optional common cable entry cubicle, the
power cables have to be routed in the base frame or in a duct under the filter to the
common cable entry cubicle where they can be connected on to the central bus bar
system. When the filter does not have an optional common cable entry cubicle, the same
connection approach as used for the other filter units must be adopted. More
information on how to connect a PQFM cubicle to the power supply can be found in
Section 6.8
