Thermal Performance of Distribution Transformers in Underground Vaults: II - Mathematical Model

The transient thennal response of buried distribution transformers is analyzed by use of a lumped-parameter model. Curves are presented which show the temperatures in the transformer r during startup and continuous running with typical load cycles, steady loads, and step loads. The effects of earth conductivity y and radiation barriers are considered. Temperatures, time constants, and convection coefficients are found to agree well with experimental measurements.