Relationship between static electrification of transformer oils with turbidity and spectrophotometry measurements

• Electrostatic charging tendency of fresh and aged oils were investigated in a spinning disk system.
• The electrification currents were related to classical aging indexes.
• Two testing procedures developed by ASTM were used to monitor decay products as trace impurities.
• The electrification currents increase with temperature, fluid velocity and disk properties.
• The electrification is definitely related to turbidity and spectrophotometry measurements.

The paper presents the research results on electrostatic charging tendency (ECT) of transformer oil in a spinning disk system. The measurements were performed at different aging severity. Changes in static electrification were related to some classical aging indexes (conductivity, dissipation factor, water content, resistivity, etc.). Fast, inexpensive and reliable laboratory testing procedures developed by ASTM (D 6802 and D 6181) were also used to monitor the decay products as trace impurities. The obtained results show that static electrification currents increase with temperature, oil flow velocity, coating disk material properties and oil’s aging byproducts. The polarity, the amplitude and the time constant of the streaming electrification currents are also affected. This contribution is not only intended to provide a fresh review in this domain of research, but also contains a substantial amount of new material with a view of closing some gaps in the present state of knowledge of transformer oil streaming electrification phenomenon.