Estimation of the hottest spot temperature (HST) in power transformers considering thermal inhomogeniety of the windings

• Published in: IEEE transactions on power delivery Vol. 19; no. 4; pp. 1704 - 1712
• Main Authors: Pradhan, M.K., Ramu, T.S.
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01.10.2004; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Applied sciences; Coils (windings); Cooling; Dielectrics and electrical insulation; Electric power generation; Electrical engineering. Electrical power engineering; Electrical insulation; Exact sciences and technology; Exact solutions; Fourier transforms; Mathematical analysis; Mathematical models; Petroleum; Power electronics, power supplies; Power transformer insulation; Power transformers; Temperature; Thermal conductivity; Thermal degradation; Thermoelectricity; Transformers; Transformers and inductors; Windings; winding thermal conductivity; Electrical insulation; transformer insulation; Thermoelectric properties; Degradation; Thermal conductivity; prediction accuracy; Electrical characteristic; Thermal conduction; Machine windings; Temperature distribution; Thermal insulation; Power electronics; Correction factor; Power transformer; Empirical model; Thermal properties; Heat source; Location of hottest spot temperature (HST); Thermal power; Thermal insulating material; Analytical method; Electric resistivity; Thermal model; Heat transfer
• ISSN: 0885-8977; 1937-4208
• DOI: 10.1109/TPWRD.2004.835291

The degradation of electrical insulation in transformers is traced to thermoelectric processes. Existence of localized hot regions due to thermal insulating properties of electrical insulation would cause thermal runaway around these regions. In an earlier paper , the authors presented analytical methods for estimating the temperature and its distribution at different points of the transformer based on a closed-form mathematical technique using a generalized heat conduction (GHC) model. Certain aspects of the inhomogeniety of the several components of the winding and incorporation of distributed heat source were not addressed. Also, a rigorous treatment involving the changes in winding resistance, which was built into the thermal model as an empirical correction factor, has now been modified and incorporated in the GHC. These considerations have now improved the accuracy of estimation of hottest spot temperature.