Abstract: Power transformers are one of the most critical components of power systems and
must be reliably protected against faults. Differential relays are widely used in the protection of
power transformers. However, these relays are susceptible to erroneous inrush currents generated
during the starting of transformers. This paper presents a new method for detecting flame currents
based on moving window averaging of the current. The study found that using the Blackman Harris
window over other windows in this method significantly reduced error detection time. The proposed
method is robust to strong noise such as white Gaussian noise. Finally, the proposed method is
compared with commonly used methods in industrial protection relays. In this comparison, it was
demonstrated that the method has several advantages over conventional methods, including the
ability to detect high second harmonics and faults below the saturation level of the current
transformer and allow for correct operation in modern transformers. The protection of power
transformers, which are the most vital components of power systems, is of great importance for the
reliability and operation of the power system.
Keywords: power transformers, fault detection, rated current, differential relay, protection of
power systems, moving window averaging