Influence of Defect Type and Position in Composite Insulation Interfaces on Electric Field Distribution Within Variable Speed Pumped Storage Generator Rotor Windings

Abstract

As a vital component during unit operation, the anti-corona layer and the main insulation composite interface of the variable speed pumped storage generator’s rotor winding are crucial for the safety of the entire hydroelectric system. This research presents a simulation of the prototypical defect types that may arise during the manufacture and operational placement of such rotor windings. An analysis of six interface defect structures within the winding’s anti-corona layer and main insulation composite interface—specifically bubbles, air gaps, water droplets, water films, metal particles, and metal spikes—is conducted. Using an electric field simulation model developed for these rotor winding composite insulation interface defects, the patterns of electric field changes at the composite insulation interface under different defect scenarios are examined. The findings indicate that under a 3-kV low-frequency square-wave voltage stress, the maximum electric field intensity distortions at the composite insulation interface caused by bubble and air-gap defects are approximately $4.57\times 10^{{5}}$ and $9.7\times 10^{{5}}$ V/m, respectively. It is observed that as bubble defects increase in size, there is a marginal reduction in electric field distortion. For water droplet and water film defects, the greatest distortion electric fields are identified as $4.04\times 10^{{5}}$ and $1.04\times 10^{{6}}$ V/m, correspondingly. The increase in the size of water droplets and films results in decreases in maximum distortion fields by 27.2% and 93%, respectively. Metal particle and spike impurities produce the most extreme distortion in electric fields, with maximum values at $1.06\times 10^{{6}}$ and $1.38\times 10^{{6}}$ V/m. Relative to other defect types, the distortions caused by metallic contaminants at the composite insulation interface are found to be the most severe. The research results can make up for the shortcomings of experimental investigation and have important reference value for winding fault analysis, operation and maintenance, and structural design.