Eelectrostatic Charging Tendency of Transformer Oils

Three different comnercially avaiTable transformer oils were evaluated for their electrostatic charging behavior. One of these oils was found to have a higher charging tendency than the others. The charging behavior of this oil was moisture dependent; drying of the oil raised the charging level while addition of moisture lowered it. All the oils showed similar temperature dependence on charging behavior in a near exponential manner. Associated with high charging behavior was higher than normal electrical conducti vi ty and lower interfacial tension. The charging tendency is attributed to certain polar compounds in trace quantities, most likely surface active agents. These substances may be present in the refined oil or introduced later in the processing and handling stages.