The improved thermal-circuit model for hot-spot temperature calculation of oil-immersed power transformers

Based on improvement of Swift's black-box thermal-circuit model, this paper establishes a dynamic numerical model suitable for different capacity transformers. According to effect factors of the precision of thermal-circuit model, such as winding losses, oil viscosity changes, heat dissipation conditions, et al, this paper proposed ways to modify the model. The model is proved to be precise by comparing results with factory temperature rise test data.