Effect of Oil Duct Spacer Quantity on Top-Oil and Hot-Spot Temperatures in Distribution Transformers

This paper investigates the influence of oil duct spacer quantity on the temperature distribution of oil-immersed distribution transformers using a multiphysics coupling method. A 100 kVA transformer simulation model was established to analyze the variation trends of hot-spot temperature and top-oil temperature under different numbers of spacers. The results show that increasing the number of spacers narrows the oil duct, raises flow resistance, and restricts oil circulation, thereby causing significant increases in both top-oil and hot-spot temperatures, with an approximately linear relationship between the two. The temperature rise curve indicates that when the number of spacers ranges from 6 to 18, the temperature increases slowly; however, beyond 18 spacers, the temperature rises rapidly. Further analysis of winding displacement and stress reveals that too few spacers result in insufficient winding support strength, while too many lead to excessive temperature rise. Considering both thermal and mechanical performance, the optimal spacer quantity for this transformer model is determined to be 16–22.