Modeling the Winding Hot-Spot Temperature and Aging of Enclosed Vault Transformers using a Physics-Based Heat Transfer Model

Meter-level data, such as those available through advance metering infrastructures (AMI), have enabled extensive monitoring and control of the electric distribution system. In this work, we develop and apply a physics-based model to simulate the heat transfer dynamics for distribution transformers in underground enclosed vaults with no ventilation. The resulting model compares well with predictions from an established semi-empirical model and in field measurements. The model suggests that the transformer aging may be significantly under-estimated, by as much as a factor of ~4, by well-established semi-empirical models for these enclosed submersible transformer applications. Results also show that system-wide application of the model provides transformer-specific insights which should help guide planning and maintenance.