Analysis of flow electrification parameters of power transformer oils

As a part of a research program at EDF, University of Poitiers has developed a prototype of a sensor dedicated to the monitoring of oil flow electrification through transformer pressboard-made channels. This phenomenon can be responsible for destructive breakdowns when the resulting charge accumulation leads to high electrical fields. In order to identify transformers running electrostatic hazards, an experimental setup been has developed to measure the generation and the accumulation on pressboard surface of electric charges with regard to different oil flow conditions (velocity, temperature). Various oils have been characterized with the same reference pressboard: new oils and oils coming from operating transformers (healthy or suspected to develop the phenomenon). The analysis of the measured parameters makes it possible to derive some criteria with regard to the electrostatic hazard probability in transformers.