A moving window average method for internal fault detection of power transformers

Abstract

Power transformers are among the mos]t critical components of power systems and should receive reliable protection against faults. Differential relays are widely used in the protection of power transformers. However, these relays are susceptible to mistaking the inrush currents, which are generated during the turning on of transformers. This paper presents a new method for detecting inrush currents based on the moving window averaging of current. The study found that using the Blackman Harris window rather than other windows in this method significantly reduces fault detection time. The proposed method is robust to strong noises such as white Gaussian noise. Finally, the proposed method was compared with the methods commonly used in industrial protection relays. In this comparison, it was demonstrated that the method offers several advantages over conventional techniques, including the ability to detect faults with high second harmonic and under current transformer saturation and to function properly in modern transformers.

Keywords

• Inrush current
• Differential relay
• Power systems protection
• Moving window averaging (MWA)