Research Of Transient Leakage Magnetic Field And Short-Circuit Strength Of Cable Winding Transformer

Cable winding transformer is a new type power transformer which is based on crosslinked polyethylene cable windings. Compared with conventional oil-immersed power transformer, it has higher safety and reliability because of this special configuration. The study on structure and property of cable transformer is not only good for optimizing its design, but also provides a new direction of transformer's development.A math model is presented for cable transformer leakage magnetic field based on coupling finite element method (FEM) of magnetic field and circuit. Short-circuit test is simulated based on the coupling model, and then the short-circuit impedance of transformer is calculated directly. It is proved that the coupling FEM of magnetic field and circuit is applicable in cable winding transformer when the FEM simulation results are good consistent with the theoretical formula results.The electromagnetic and short-circuit property of cable winding transformer is analyzed by using coupling FEM of magnetic field and circuit which applicability is proved. First of all, the distribution of transient leakage flux is obtained based on the analysis of transient leakage magnetic field when short-circuit happened. Then, the peak value of short-circuit current and the distribution of short-circuit current at time process are calculated. Thirdly, short-circuit electromagnetic forces for every turns and frequency spectra of short-circuit electromagnetic forces were calculated. Finally, short-circuit strength of transformer was calculated and verified based on the Fourth Strength Theory.Vibration analysis of power transformer is very important for the reliability and durability. Some researches have shown that the most of the failures were caused by the axial vibration of the windings. The model of axial vibration was proposed to calculate the frequency of windings as well as to analyze the vibration patterns and internal forces of windings both in time-domain and frequency-domain.The whole analysis of short-circuit property of cable winding transformer may serve reference value in cable winding transformer technology and even in conventional transformer technology.