5.1.5 Application
Transformer protections require high stability to avoid tripping during magnetizing
inrush conditions. A typical example of an inrush detector application is doubling
the start value of an overcurrent protection during inrush detection.
The inrush detection function can be used to selectively block overcurrent and
earth-fault function stages when the ratio of second harmonic component over the
fundamental component exceeds the set value.
Other applications of this function include the detection of inrush in lines
connected to a transformer.
Figure 420: Inrush current in transformer
It is recommended to use the second harmonic and the waveform based
inrush blocking from the transformer differential protection function
TR2PTDF, if available.
1MRS757644 H Protection related functions
620 series
Technical Manual
803
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