Development and calibration of a streaming electrification model for a cellulose duct

Streaming electrification occurs in large power transformers where insulating oil circulated for cooling purposes acts to separate charge from the interfacial double layer present on a multitude of cellulose insulation surfaces. In this paper, the electrification phenomenon is addressed from a microscopic viewpoint. An empirically calibrated analytical model is provided for calculating the amount of charge separated in a core-form transformer duct. The model incorporates a boundary layer approach in approximating the wall charge distribution which provides a critical length scale for the analysis. This length scale is used to specify the appropriate model for charge development under turbulent flow conditions. The duct model considers both laminar and turbulent flows subject to ac electric fields and varying temperature. This concept forms the elemental building block of a network-based methodology for examining electrification in a complete transformer geometry