Thermal Capacitance Calculation of Top-Oil Temperature for Power Transformers

Iskender I., Mamizadeh A.

INTERNATIONAL REVIEW OF ELECTRICAL ENGINEERING-IREE, vol.4, no.5, pp.882-886, 2009 (SCI-Expanded) identifier identifier

  • Publication Type: Article / Article
  • Volume: 4 Issue: 5
  • Publication Date: 2009
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus
  • Page Numbers: pp.882-886
  • Van Yüzüncü Yıl University Affiliated: No


Transformer life has a considerable economic impact on the operation of an electrical network. The most important parameter in transformers life expectancy is the insulation temperature value. The variation of the temperature is described by an exponential equation based on the time constant of the system. In the thermal equivalent circuit model the time constant is equal to multiplication of thermal capacitance and thermal resistance. The aim of this paper is to present an equation for calculating thermal capacitance of oil immersed transformers that have assorted materials as conductor in their windings. In most transformers the primary and secondary windings conductor is copper, but now transformers are designed and constructed with aluminum as conductor in both primary and secondary windings, or one of them may be aluminum and the other copper. This work describes a method for calculating thermal capacitance of top-oil temperature for oil immersed transformers which is in accord with the IEEE Std C57.91-1995 Annex G, suitable for both aluminum and copper windings. The equation proposed in this work is confirmed by experimental works applied on three different oil immersed transformers. Copyright (C) 2009 Praise Worthy Prize S.r.l. - All rights reserved