Flow electrification in power transformers: study of a potential remedy

Understanding the exact nature of the phenomena at the origin of the electrical charging tendency of transformer pressboards submitted to oil circulation in high power transformers is still a challenging problem. Former studies demonstrated that flow electrification depends in a large part on the chemical functional groups of the pressboard surface, and especially carboxyl groups. In this study, the action of several additives has been tested. Three experimental devices (conductivity cell, flow loop and electrostatic charging tendency tester) have been used to investigate the effect of the additives on the charge generation, accumulation and leakage currents. Moreover, experiments with demineralised pulps treated by carboxyl complexing agents such as methylene blue have confirmed the important role of ionisable groups in paper. Some additives were found to reduce the electrification phenomenon. A comparison between these results and some aspects of ionic chromatography could be done, and the related theory can be attempted to explain the chemical process which takes place between the oil and the pressboard