Transformer Magnetizing Inrush Current Formation Mechanism And The Current Transformer Simulation Model

This research of this paper focuses on transformers and current transformers. The main contents are as following:1) In this paper, the decaying mechanism of transformer inrush currents is analyzed. A recurrence approach to calculate decaying inrush currents is derived base on the transformer equivalent circuit. Practical formulas for the dependence of dead angle and inrush current amplitude on time are presented by curve fitting. It provides a tool of analysis and calculation for the research on differential protection and backup protection.2) The phenomenon of sympathetic interaction between transformers is very likely to occur when a transformer is energized onto a system to which other transformers already connected. Base on the transformer equivalent circuit and the flux variety, the principle and characteristic of sympathetic interaction is studied in depth. Finally, the effecting parameters are investigated such as system resistance, parallel or series of transformers, and the load of connected transformer.3) The modeling methods of current transformer are analyzed, especially on the excitation character. A program base on the optimized model is written to simulate current transformers. It is useful on the research of relay protection.