Frequency response analysis to investigate deformation of transformer winding

This paper discusses the application of Nyquist plot and two statistical indicators to analyze the frequency response of power transformers. Five cases are presented based on both simulations and measurements. These include two types of winding deformation, namely tilting and bending of conductors. Initially, damage is simulated for five degrees of severity and analyzed using two statistical indicators. The indicators are compared for their performance in terms of evaluating the severity of damage. New findings from this comparison are presented. Additionally, the benchmark limit for one of the indicators is also assessed on all cases. Finally, a methodology is proposed to estimate the severity of damage from two frequency responses using the Nyquist plot. This method is tested on three different windings.