Internal Short Circuit Current Calculation and Dynamic Simulation of Converter Transformer

Studying the distribution characteristics of the short-circuit current in different positions under the internal fault of the converter transformer can deepen the understanding of the fault mechanism and provide an important reference for its protection research. The axial ampere-turns distribution of the converter transformer is not uniform, which causes a significant increase in the transverse leakage magnetic field component. In this paper, after the winding resistance parameters are corrected by the radial short circuit resistance of the internal fault, the short circuit winding and the remaining winding are treated equally, the equivalent circuit model after the internal fault is optimized, and the calculation method of inter-turn short-circuit current is proposed. The defined no-load running inter-turn short-circuit reactance ratio K can be used to describe the ratio of the current in the short-circuit circle to the short-circuit current at power grid side after the inter-turn fault of the converter transformer. The engineering products are taken as prototypes, and the consistent technical index of the physical model of the converter transformer is proposed. Through the simulation comparison with a prototype product, the law of the inter-turn short circuit current distribution is put forward. Affected by the fault location, the short circuit current with the same turn ratio presents the saddle-shape distribution characteristics from the coil axis. Furthermore, a physical model of the converter transformer is developed that can reflect the internal short circuit fault. Finally, a fully physical dynamic simulation test platform for the internal faults of the converter transformer is built to verify the correctness of the proposed internal short-circuit current calculation method, and the calculation error of its K value is controlled at −1.70%~0.72%. © 2024 Science Press. All rights reserved.