Application of enhanced thermal ratings to primary substation transformers

The use of thermal modelling to increase the permissible load-carrying capability of distribution system transformers is attracting increasing interest. Many reported approaches calculate the rating of transformers in real time in response to system conditions. In this study, an experiment to validate and tune the parameters of such a thermal model is described, and explained how the results have been used to inform the inclusion of model-based seasonal ‘enhanced’ ratings in the network planning process.