Calculation of Axial Short-Circuit Strength of Distribution Transformers Under the Influence of Axial Pre-compression Force

The insufficient axial short-circuit withstand capability of distribution transformers poses a serious threat to the stability and safety of power system operation. To address this issue, this paper takes a 100 kVA distribution transformer as the research object and analyzes its short-circuit current characteristics, leakage flux distribution, and axial electromagnetic force distribution under a three-phase short-circuit condition. Furthermore, the key manufacturing factor influencing axial short-circuit performance, namely the degree of axial pre-compression applied to the windings, is identified. Numerical simulations are then conducted to evaluate and compare the axial short-circuit performance of the transformer under different process parameters, and the optimal parameter range that effectively enhances axial short-circuit strength is determined. Based on the simulation results, two prototype 100 kVA distribution transformers with different manufacturing conditions were fabricated. Short-circuit withstand tests were carried out to verify the accuracy of the simulation results and to confirm the effectiveness of the proposed method and conclusions.