A study into improving transformer loading capability beyond nameplate rating

Utilities are becoming increasingly interested in the prospect of overloading the transformers beyond the nameplate rating to meet the increased demand for power as it may be more economically viable than installing a new transformer. The safety of the transformer has to be ensured while overloading it and hence there is a maximum loading beyond which the transformer should not be overloaded. A study has been performed on 38 transformer units and the factors that limit their overloading capability have been analyzed. Ancillary equipment ratings were found to be the most prominent limiting factor. Several case studies and evaluation results have been provided to establish this. A new practice for selecting ancillary equipment has been proposed that will improve the transformer overloading capability significantly. Analytical results have been provided to demonstrate the effect the proposed solution will have on transformer overloading capability.