Experimental evaluation and simulations of X-wax in transformer bushings

The high voltage condenser bushing is a critical component found in all electrical networks and whose failure can have serious consequences. Thermal and electrical stresses, ambient conditions, and other factors place high demands on bushings. Proper condition assessment is essential to maintain a high system availability. The most commonly used advanced tools are the Dielectric Frequency Response (DFR) analysis on bushing's condenser body and the Dissolved Gas Analysis (DGA) on oil samples. The present article summarizes the results of an extensive investigation where these tools have been used to analyze bushings both in field and in laboratory environment. By combining the information obtained from the DFR curves and the results of the DGA a pattern specific for presence of x-wax could be discovered. More detailed investigations of x-wax impregnated paper were performed and the results were then used in Computational Fluid Dynamics (CFD) describing the thermal response of bushings with x-wax.