ABB PQFM Instruction Manual page 57

In order to determine the suitable CTs for your application, please refer to the chart in
Figure 35.
Remark: In some applications two or more power supplies exist (e.g. a network
transformer supply and a generator supply). When the current into both supplies has to
be filtered, summing CTs have to be used. All summing CTs must have the same ratio.
More information on how to install the summing CTs is given in next section.
Manual Power Quality Filter PQFM ç Electrical design and installation 57