A Method of Improving Transformer Overloading 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. However, 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. In this paper, we present results and insights based on an extensive study performed on 48 transformer units and an analysis of the factors that limit their overloading capability. We observe that the ancillary equipment ratings are the most prominent limiting factor. This is confirmed by several case studies and evaluation results. We propose a new practice for selecting ancillary equipment that will improve the transformer overloading capability significantly. We also present analytical results to demonstrate the impact of our solution on transformer overloading capability