Controlled switching strategies for transformer inrush current reduction: A comparative study

Transformer inrush current can be efficiently mitigated by controlled switching. For energization of three-phase transformers, several strategies have been developed that depend on whether the residual flux can be measured and whether independent-pole-operated or three-pole-operated circuit-breakers are used. In this paper, a comparative analysis of these strategies has been carried out. Residual flux uncertainty and dispersion of the characteristics of the circuit-breaker can significantly affect the performance of the controlled switching. These issues have been taken into account in the analysis of each strategy since they can influence the performance in different ways. The study has resulted in the selection of the most appropriate strategy for each case.