The Research On Leakage Magnetic Field And Short-circuit Characteristic Of Large Transformer Winding

The ability to withstand short circuit of transformer is one of its important characters, having respect to normal work of power system.The dissertation begins with the analysis on leakage magnetic field, then represents a method utilizing Finite Element and Numerical Analysis to calculate leakage field. Then It analyzes several short-circuit currents. Based on short-circuit impulse current, the law of electromagnetic induction and Ampere force law, considering the actual construction winding, it divide the short-circuit force into radial and axial force, and elaborate the cause of the two forces. discuss the influence of the short-circuit force's time variation and the innate vibration frequency. And some computing methods to calculate axial force, axial bending strength, Radial Force, Radial Stability are deduced.Using the method above, it models and makes subdivision of a transformer which passed a short circuit test, then calculates it. Distribution of leakage field in the transformer and curves of magnetic potential along the axial orientation are obtained. And the calculated value of parameters on short-circuit force are obtained, too. Comparing the calculated value with the standards issued by authority, the paper testifies the method is right. Having analyzed leakage field's distribution and the curve, it obtains some relationships of the short-circuit force and some factors such as terminal winding's bending , imbalanced ampere-turn.Finally, the influence on the short-circuit force, produced by degree of windings'axial malposition and the numbers of supporting profiles, is reckoned by simulation. And some helpful conclusions to designers and users are acquired.