Abstract：With the construction of ultra-high voltage lines, large-capacity transformers have been widely used. In order to improve the reliability of power supply, Yy connections with neutral points that is not grounded is often used in large-capacity transformers. However, this will cause the third harmonic voltage with large amplitude in the output induced electromotive force of the winding, which endangers the safe operation of the power system. To solve this problem, a set of additional windings is added to the transformer. As the third winding of the transformer, the additional winding has the function of providing a path for the third harmonic current and reducing the aberration rate of the induced electromotive force at the output of the transformer. This article uses Ansys Maxwell finite element simulation software to calculate the transformer core loss, secondary side induced electromotive force and output power when the transformer with additional winding Yy is connected with rated load. Through the differential setting of the number of turns and positions of the additional windings, the best additional winding parameters are obtained by comparison. The finite element simulation results prove that when the additional winding is delta connection, the capacity is one-fifth of the transformer capacity, and the distribution position is high-additional-low, the transformer core loss is reduced, and the third harmonic component in the output induced electromotive force is significantly reduced.
2021, Vol. 22 
