Dynamic loading of substation distribution transformers in a production grade environment

This paper introduces a planning tool developed for estimating the maximum time-varying (dynamic) load that a substation distribution transformers can tolerate without violating hottest-spot (HST) and top-oil temperature (TOT) thermal limits. Presented are two kinds of HST and TOT models: the traditional ANSI Clause 7 models and linearized thermal models with coefficients optimized through linear regression to reveal the relationship between HST, TOT, ambient temperature and load. These models, along with Newton´s method, are shown to be capable of performing dynamic loading calculations.