Winding Temperature Analysis of 3-D Wound Core Transformer Under Overload and Short-Circuit Conditions

摘要

Wound core transformer is widely used in power distribution because of its low no-load loss and small size, which required to withstand overload and sudden short-circuit conditions due to load variation, so it is necessary to predict and simulate the overload and short-circuit tolerant capacity of the transformer. In this paper, a finite element methodology based on electromagnetic-fluid-thermal coupling for the analysis of a 3-D model of dry-type wound core transformer is proposed. The loss distribution of the transformer is calculated under rated, overloaded and short-circuit conditions, respectively, which is taken into the fluid-thermal field account for analysis of transformer as heat source. The influence of temperature change on air parameters is considered for better accuracy. It is found that the 3-D wound core transformer has the capability to withstand 1.2 times overload capacity and the successive running time is obtained under different overload levels. Moreover, the simulation results show that the transformer is unable to withstand repeated short-term short-circuit conditions due to the cumulative effect of winding temperature. The results are compared with the empirical formula proposed in International Electrotechnical Commission standard, which proves the validity of the finite element method coupled with electromagnetic-fluid-thermal field.