New Methodology for Identification of Sympathetic Inrush for a Power Transformer using Wavelet Transform

This paper presents a new methodology to identify the transient of sympathetic inrush between power transformers that aims to prevent the protection system from being affected by this transient. The developed method is based on the variation of the detail coefficients of different levels of DWT decomposition. During the sympathetic inrush condition, the detail coefficients present a different variation from that which occurs during an internal fault condition. The proposed methodology is able to identify the sympathetic inrush conditions without the need to set a threshold, making the methodology intelligent and avoiding unwanted trip of the protection system. The proposed methodology was thoroughly tested and proved to be promising in the identification and discrimination between sympathetic inrush and internal faults.