ABB RED615 Technical Manual page 406

Section 4
Protection functions
400
GUID-799588E3-C63F-4687-98C5-FF48284676DF V1 EN
Figure 215: Differential protection of a three-winding transformer and a
transformer with two output feeders
TR2PTDF can also be used for the protection of the power transformer feeding the
frequency converter. An interposing CT is required for matching the three-winding
transformer currents to a two-winding protection relay.
The fundamental frequency component is numerically filtered with a Fourier filter,
DFT. The filter suppresses frequencies other than the set fundamental frequency,
and therefore the IED is not adapted for measuring the output of the frequency
converter, that is, TR2PTDF is not suited for protecting of a power transformer or
motor fed by a frequency converter
1YHT530004D05 D
615 series
Technical Manual