Hi All,

I am working on electric discharge and breakdown of lubricants (synthetic Group IV) under applied DC. I have observed that when a potential exceeding breakdown voltage is applied the voltage response shows gradual breakdown rather than immediate. I have done some literature survey where I found similar base oil transient DC current response due to relaxation of dipoles in the oil [1][2]. However, most of these tests have been for static oil film or shows constant current when lubricant is flowing. Whereas, in my test the oil film is not static and has certain velocity. I have also found that breakdown happens at same time interval regardless of flow velocity. I have added a discharge trend in which it shows that number of discharges increases as voltage is increased reaching a certain level before dropping (breakdown). Why the breakdown happens gradually at this voltage level?

[1]. A. Rosenkranz, B. Martin, S. Bettscheider, C. Gachot, H. Kliem, F. Mücklich. Correlation between solid–solid contact ratios and lubrication regimes measured by a refined electrical resistivity circuit, Wear, Volume 320, 2014, Pages 51-61, ISSN 0043-1648, https://doi.org/10.1016/j.wear.2014.08.018.

[2] H. Miyao, M. Higaki, Y. Kamata. Influence of AC and DC Fields on Streaming Electrification of Transformer Oil. in IEEE Transactions on Electrical Insulation, vol. 23, no. 1, pp. 129-135, Feb. 1988, doi: 10.1109/14.2346.