Validated transient heat-transfer model for underground transformer in rectangular vault

Julien Sandraz, Francisco De Leon, Joseph Cultrera

Research output: Contribution to journalArticlepeer-review


A new thermal model for underground transformers is proposed in this paper. The model takes the following important characteristics of the transformer installation into account: rectangular shapes; coil and core arrangement; orientation-based convection models for air (vertical, horizontal-upward, and horizontal-downward heat flows); and turbulent or laminar flow regime. The resulting coupled set of differential and algebraic nonlinear equations is solved simultaneously, providing a robust and fast solution that can help design transformers. The model has been validated against three transformers with different dimensions installed in different vaults with onsite measurements. The average absolute difference between the simulated and measured temperatures over several months is typically less than 4°C. A parameter sensitivity study shows the critical importance of the proper estimation of the full-load heat loss and the ambient soil temperature.

Original languageEnglish (US)
Article number6516999
Pages (from-to)1770-1778
Number of pages9
JournalIEEE Transactions on Power Delivery
Issue number3
StatePublished - 2013


  • Distribution transformers
  • heat-transfer transients
  • predictive maintenance
  • thermal analysis
  • thermal circuit

ASJC Scopus subject areas

  • Energy Engineering and Power Technology
  • Electrical and Electronic Engineering


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