Suspended Particles in Oils under Electrical Discharge

Since gas evolvement deteriorates the dielectric properties of insulating fluid, its ability to resist decomposition under electrical discharge is of paramount importance for the safety of power transformers. In this contribution, the ability of various fluids to resist decomposition under electrical discharge is investigated. Mineral based transformer oil was included in the test matrix to provide a base line to which high fire point (HFP) liquids could be compared. The impact of the fluid's purity on its gassing is quantitatively determined by particles counting. The obtained results revealed that the higher the gassing tendency, the higher the particles generation tendency is. It was also found that natural esters generate fewer gases and particles than the other fluids. The mixture of 20% of natural ester with mineral oil depicts an intermediate behaviour.