Instantaneous power based detection of inrush currents in single phase transformers

The inrush current during transformer energization leads to protective relays mal-operations and power quality issues. The state of the art technique for the transformer inrush current detection involving the determination of second harmonic content in the current waveform fails in modern transformers as this is inherently less in them. This paper proposes a new simple and effective technique based on the instantaneous power computations for the detection of inrush currents from fault and load currents. Exhaustive investigations are carried out by simulating a single phase transformer for different fault and switching conditions. Simulation studies reveal that the proposed technique finds potential application in detection of inrush current in modern single phase transformers.