Streaming electrification study of transformer insulation system using a paper tube model

A simple flow model was designed to simulate oil flow in the insulation ducts of power transformers. It consisted of an annular paper tube, relaxation tanks, pump, and flow controls. Laminar and turbulent flow modes were studied in the temperature range from 27 to 70°C. Current development was monitored as a function of temperature and flow velocity. The temperature dependence was approximately of the Arrhenius type; no current peak was observed as reported for transformers in the temperature range studied. The current increased linearly with flow velocity at low flow rates and increased as the square of velocity at high flow rates with a gradual transition in the intermediate range of flow. The voltage development was characterized by a sharp rise initially as the flow was turned on, leveling off to a maximum after several minutes. Partial discharge patterns were observed in the volt-time plot, increasing in frequency and temperature at elevated temperatures and flow velocities. A strict application of the test results to transformers is not possible due to unknown parameters