Research on streaming electrification of insulation mineral oil

As we know, streaming electrification due to oil flow is an important phenomenon in power transformers particularly on those high rated voltage ones, and the study around it is still a challenge. In this paper, the streaming electrification characteristic of insulation mineral oil from Nynas was studied by using an improved mini-static tester to measure the electrostatic charging tendency (ECT) of oils with different aging conditions. The oil samples were aged under 120degC in different periods up to 1350 hours, and together with different contents of oxygen and a certain amount of copper and pressboard. A comparatively better linear correlation is shown between ECT and volume resistivity (rhov), dissipation factor (tandelta) and water content, The tandelta and water content are increasing gradually with the aging time prolonged, while rhov and carboxyl decrease slowly, the acid number does not present evident fluctuation during the whole aging periods.