Research Of Mechanical Force And Torsional Deformation For Large Transformer Winding

Because of the low voltage winding of large transformer mostly adopts single or multi helical structure,and the current flowing through the winding even up to tens of thousands of ampere.Thus there is a large axial current component in these windings.When the transformer is short circuited,the short-circuit electric force of the helical winding will contain a lot of tangential force,so it will rotate and twist.Different from the winding of general structure,the effect of tangential force must be taken into account for the large current helical winding,and the torsion problem under the action of tangential force and torque must be analyzed.In this background,firstly,it established a model of SSZ11-50000/110 transformer which has passed short circuit test to analog three-phase short-circuit state by using Comsol software.The instantaneous short circuit current,two-dimensional transient electromagnetic field,radial and axial short circuit electromagnetic force were analyzed for the short circuit time within 0.12 s time of the transformer.The stress of winding wire is calculated by using the stress calculation formula.Then,the two-dimensional model of the transformer is established by using the electromagnetic field software.The stress of the short circuit electromagnetic force、short-circuit impedances and stress of winding wire are calculated.The method of gb1094.5-2008 is adopted to verify the anti-short-circuit capability of the product,and the result shows that the product has sufficient anti-short-circuit capability.The validity of the calculation method is proved by comparing the two simulation results.Finally,the influence factors of the results are analyzed and the measures to improve the performance of short circuit are put forward.A coupling model of two dimensional and three dimensional magnetic field-structural force field of helical winding are established by Comsol.The tangential force size and distribution law of the low voltage helical winding are obtained.It tested the reliability of the calculation method through the comparison and analysis of two kinds of modeling.On the basis of this,it studied the influence of helical angle 、magnetic shielding and axial compression force on the tangential displacement of helical winding.The results show the method is efficient for reducing winding tangential displacement in product design.Theanalytical methods are useful for the calculation and verification of large,ultra-high voltage power transformer winding short-circuit electromagnetic force with helical winding.