Selecting overcurrent protection for three-phase transformers

In this article, the authors discuss power transformer protective system philosophies and illustrate the selection alternatives through examples. Transformer inrush currents, overload capability, protective device performance for different fault types, winding connections and the impact on operating concerns are discussed. Their emphasis is on power transformers applied within an industrial facility that are rated 2500 kVA and below, and where the overcurrent device is normally a fuse.