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This paper presents a practical thermal loading guide for distribution transformers feeding residential customers. Extensive load research data were used to estimate the thermal response of a "standard IEC distribution transformer." A strong relationship between the parameters of a load modeled by load current as a function of time and the hotspot temperature was found. Using this type of load model, a method was developed for estimating the hotspot temperature of a transformer for customers from different load classes. A method was derived to translate the thermal response of a standard IEC distribution transformer to any practical transformer.
Date of Publication: Aug. 2004