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

Abstract

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 turbulmt flows subject to ac electric fields and varying temperature. This concept forms the elemental building block of a network-based methodology for examining electrification i n a complete transformer geometry.

A parametric study of streaming electrification in a full-scale core-form transformer winding using a network-based model

“…A network-based representation of a complex transformer geometry is assembled using a detailed duct electrification model [1] as the basic element. Matrix descriptions of the structure are defined to facilitate sequential computation of the individual duct flow rates, charge densities and static potentials.…”