WATER TREEING IN INSULATING LIQUIDS

Water has been found to migrate through an insulating fluid under the influence of a 50 Hz divergent electric field and to form treelike structures of water-filled channels at points of high electrical stress. Growth was dependent on the presence of ions in the water in contact with the insulating liquid. Dielectrophoretic forces on such hydrated ions, in the nonuniform electric field between needle-plane electrodes, is believed to be responsible for the observed accumulation of water at the needle tip and the subsequent development of tree-like structures. These developments were influenced by the hydration factors of the ions present in the liquid. They were also influenced by the viscosity of the liquid as was demonstrated for a wide range, through the use of silicone fluids.