Digital Filtering Algorithms for the Differential Relaying of Power Transformer: An Overview

This paper reviews the digital differential relaying algorithms proposed by different authors for the protection of power transformer and compares them as to their speed of response, computational burden, and the capability to distinguish among an inrush, over-excitation, and transformer internal fault. The mathematical basis of each algorithm is described. All the algorithms are capable of discriminating an inrush, over-excitation, and transformer internal fault.