Modelling of Oil-filled Transformer
Marius-Constantin O.S. Popescu, Nikos E. Mastorakis, Liliana N. Popescu-Perescu
Abstract—The purpose of this article is to analyse the
tansformer thermal and loss of life models will be studied. Based on the thermal model adopted by International Standards, small improvements to increase model accuracy are presented and a comparative study of resulted accuracy under different load and ambient temperature profiles is performed.
Keywords—Modelling transformer parameters, Oil-filled transformer, Loss of life models. I. INTRODUCTION HIS paper emphasizes that, given a few transformer specific parameters the hot-spot temperature can be estimated as a function of the driving load and ambient temperature. In this purpose, thermal mechanisms will be simplified, as well as the transformer thermal system itself. Based on field experiments, many authors are unanimous in considering the model given by International Standards a conservative one , , . Therefore, with small improvements of reduced complexity, more accurate hot-spot temperatures could be estimated, increasing this way, the model efficiency. However, it is not always an easy task to determine the ratio between the increase of complexity and corresponding accuracy benefits. Consequently, possible model improvements are derived: the correction of transformer losses due to temperature variation, the convective heat transfer variation with temperature, the existence of a secondary thermal time constant associated to transformer windings and the influence of variable ambient temperature into transformer dynamic thermal system . Many other aspects could be introduced but they would lead to an increase in model complexity not compatible with the required simplicity. Some kinds of ageing factors arising in electrical apparatus, such as thermal, voltage and mechanical, are briefly...