Figure 397: 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 protection relay 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
Protection functions
1MRS759142 F
696
REX640
Technical Manual