Abstract
The flow electrification phenomenon is known as a major cause of failures in oil-cooled power transformers. To improve the reliability of transformers, we need to be able to predict the electric field caused by flow electrification in a transformer. We developed a three-dimensional (3D) flow electrification simulation model to predict the wall current distributions in complex-shaped pressboard ducts that produce complicated oil flows. First, we derived a flow electrification analysis model, which reflects the correlation between local wall current density and local wall shear stress. This analysis model was verified by measured data of wall current density generated in a straight pressboard duct. Then, we applied this analysis model to 3D simulation code and simulated flow electrification in two types of channel structure, a T junction structure and a narrow oil gap structure, which represent typical structures that often appear in real transformers. We compared the simulation results with the measurement results and confirmed that the prediction accuracy of the simulation code is at the practical level for estimating flow electrification in a transformer.
