Investigating the growth of carbon traces in cardboard in oil-paper insulation

A large amount of contaminants are collected on the cardboard surface valve-side bushing outlet a converter transformer that has been operating for long period, and can cause performance oil–paper insulation to degrade. The analysis their energy spectrum shown these contain free carbon. To investigate causes formation carbon traces, authors this study analyze law growth insulating paper in presence pure oil containing particles. We examined influence tracks different lengths breakdown voltage along insulation. results showed carbonization generated traces eventually led conductive channels. Moreover, were by particles deposited grew from high-voltage electrode ground direction electric field both types oils. channel through poles required lower shorter discharge time than oil. As concentration increased, rate increased such failed earlier otherwise. Long formed case high under DC pre-pressure mode, reduction