Influence of additives and pressboard degradation on flow electrification in high power transformers

The aim of this work is a better understanding of the flow electrification process occurring in high power transformers. In order to characterize the effect of the pressboard degradation and the additive benzotriazol, the experiments consist in measuring the streaming currents generated by an oil flow through a pressboard sample. Two main results have been obtained: the addition of several ppm of benzotriazol in oil permits to reduce significantly the flow electrification process whereas the degradation of the pressboard by electrical discharges induces a high increase of the phenomenon