STATIC ELECTRIFICATION AND PARTIAL DISCHARGES CAUSED BY OIL FLOW IN FORCED OIL COOLED CORE TYPE TRANSFORMERS

This paper deals with the investigation of some special features of the static electrification which is caused by oil flow, and the conditions of occurrence of the partial discharges which are caused by electrostatic charges in forced oil cooled core type transformers which are hereinafter called transformers in this paper. At first, using simplified component models of oil flow, we investigated the basic characteristics of the electrostatic charge separation which is caused by oil flow. Second, the distribution in each part of a transformer of the electrostatic charges which are generated by static electrification were studied in actual transformers. Finally, the conditions of occurrence of the partial discharges which are caused by static electrification were investigated by increasing the total oil flow rate up to several times the rated value. Consequently, it was found that under certain oil flow conditions partial discharges took place at locations where the electrostatic charges caused by static electrification had accumulated on the surface of the solid insulating structures in transformers. Copyright © 1979 by The Institute of Electrical and Electronics Engineers, Inc.