Determination of critical ambience temperature by power transformers loading

This paper presents results of the analysis of the rate between permitted maximal peak load of power transformer x/10 kV/kV and its recorded peak load, both as functions of ambience temperature´s average daily value, 8a. Concerning the fact that these functions depend on consumption types, three different consumption areas were analyzed: with electrical, non-electrical and mixed space heating manner. Functions mentioned above were defined according to relevant annual load charts. It has been determined that both functions´ types can be approximated with S-curves or third degree functions. By these functions´ comparison, man can determine critical value of ambience temperature, by which the equivalence of thermally permitted peak load of a power transformer and its consumption area´s peak load demand, guaranties that this power transformer would not be overloaded, by any other ambience temperature.