Modelling the pre-breakdown phenomena in mineral and bodegradable oils used in power transformers

The service life of the power transformer is directly related to the quality of its insulation system. In service, under various stresses, a set of precursor phenomena may initiate breakdown in the oil. Understanding the fundamental theoretical causes of insulating liquid breakdown, that is, the conditions necessary for streamers formation, are important for proper designs. The objective of this topic is to contribute to the use of ester oils in power transformers by evaluating their performance through chemical and electrical tests. A mathematical model simulating the initiation and propagation of streamers is being developed. This modelling will make it possible to combine numerical simulations with experimental tests, with a view to reducing the number of tests – very costly – required to test and validate new fluids. Such a simulator already constitutes, and will increasingly constitute, a very useful instrument allowing identifying the role of the various parameters. This will help understanding all the phenomena associated with pre-breakdown, for predicting these phenomena and suitable configuration design.