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 the second harmonic component to the fundamental component exceeds the set value.
Other applications of this function include the detection of inrush in lines connected to a transformer.
Note: It is recommended to use the second harmonic and the waveform based inrush blocking from the transformer differential protection function TR2PTDF, if available.