Research on the Magnetic Field and Short-Circuit Impedance Characteristics of Single-Phase Three-Column Parallel Transformers

Manufacturers often adopt auto coupled coils to reduce costs for market competition. However, the increase in capacity and voltage leads to the emergence of special-structure transformers, such as yoke and disassembled transformers, which significantly differ from traditional transformers in terms of magnetic fields and losses. This paper employs a three-dimensional transient field-circuit coupling method to simulate single-phase three-limb transformers. The study investigates the current distribution and short-circuit impedance of large-capacity single-phase three-limb parallel-connected transformers during sudden short-circuit conditions, and explores methods to reduce the difference in leakage magnetic resistance of the three-limb parallel coils through the rational arrangement of tank shielding. Taking the ODFPS-1000000 kVA /1000 kV single-phase three-limb parallel-connected transformer as an example, a basic structural model of the transformer was established and simulation calculations were performed. The results show that tank shielding can effectively reduce the leakage magnetic density and eddy current loss density of structural components, thereby enhancing the operating performance of the transformer. We also study the current distribution and impedance of transformer coils, finding that there are significant errors when using traditional circuit methods for calculation. Therefore, this paper proposes a three-dimensional field-circuit coupling method for calculating the current distribution in the coils. Simulation calculations are performed to analyze the coil current, impedance, and eddy current losses in the structural components of large-capacity single-phase three-limb parallel-connected transformers. The research results provide theoretical support and reference for the design of large-capacity multi-limb coil parallel-connected structure transformers.