Static Electrification by Forced Oil Flow in Large Power Transformer

Static electrification phenomena in forced oil cooled large power transformer are studied on two full scale models of EHV transformer and some other supplemental models. The dc field due to the static charge separation by the flow of oil can possibly exceed the dielectric strength of oil to produce a discharge in oil. The important factors in the streaming electrification and the precautions for the static charge problem are discussed in this paper.