The role of dielectrophoresis in the water treeing process

Even after 25 years the water treeing phenomenon is still a technically important problem. Over the past years many efforts have been undertaken to improve the insulating materials and to find methods for reliable life predictions of cables. For both a reliable concept of the deterioration mechanism would be helpful. While advantages and disadvantages of the electromechanical and electro-chemical models are discussed in the literature, the electro-physical concept is not taken serious, because calculations of the dielectrophoretic forces under standard assumptions do not result in supersaturations supposed to be sufficiently high for precipitation of liquid water. The paper concentrates on the electro-physical concept and discusses experimental findings that cannot be explained by the electro-mechanical or electro-chemical concept. In addition it is shown, that the dielectrophoretic forces on clustered water molecules are sufficiently high to establish a critical supersaturation