Abstract
Flow electrification characteristics of transformer oil were investigated by applying dc field and dc/ac composite field with both bare and covered electrode systems. In the case of bare electrode system, it was found that flow electrification characteristics were almost the same between positive and negative dc voltage application and negative charges were generated for both dc voltage and dc/ac composite voltage applications at high dc field region. In the case of covered electrode system, it was found that apparent flow electrification characteristics were different between positive and negative dc voltage applications. For the former, negative charges were generated at high dc field strength for both dc voltage and dc/ac composite voltage applications and for the latter, positive charges always generated for both dc voltage and dc/ac composite voltage applications. However, negative charge generation for positive voltage application was considered to be the influence of negative charge generation at bare part of covered electrode end and it was found that fundamental charge generation characteristics of covered electrode were an increase of positive charge generation by dc voltage application and positive charge generation was accelerated by superimposed ac field.
