Three-Phase Transformer Inrush Current Reduction Strategy Based on Prefluxing and Controlled Switching

Inrush current with high amplitude is generated when the transformer energized. On one hand, it will have a negative impact on safety of itself, and even cause relay protection to malfunction. other may reduce operation speed there slight fault because restraint criteria. Both aspects affect grid security. Based generation mechanism inrush current, this paper proposes an reduction strategy that combines prefluxing controlled switching technology. By constructing equivalent magnetic circuit model large-capacity three-phase universal core structure, analytical formulas flux at each stage implementing are obtained, then parameters design method proposed. The accuracy theoretical analysis verified through accurate simulation. Compared common strategies, can 0.5 times rated below in any situation where residual unknown “core equalization” effect not obvious, avoiding problem measurement. Finally, case differential protection, influence analyzed from perspective theory simulation, shows improve performance various protections effectively.