Dynamics of an electrified water/air interface submited to AC voltage
Résumé
A water droplet deposited on a conductor of high voltage transmission lines vibrates with a frequency proportional to the frequency of the applied AC voltage. The droplet also deforms subsequently under 50-Hz-voltage stress. Likewise, it has been observed that the surface of a water puddle on a high voltage conductor becomes unstable from a certain value of the electric filed strength, with respect to the geometry of the conductor or transmission line. In this paper, the dynamics of a water/air interface is investigated theoretically when the electrode system containing the water droplet or water puddle is submitted to AC voltage. A mathematical model enabling us to simulate the axisymmetric deformations of droplets is used to calculate the critical electric field strength at which a water/air interface becomes unstable according to some approximation techniques, for a sessile water droplet on a metal electrode faced to rod electrode. Furthermore, this paper presents an experimental study of the deformation of a water droplet and water puddle on a plane electrode faced to another rod electrode to check the theory. Fundamental observations of current discharges characteristic of water/air interface are presented. The behaviour of the inception field strength of partial discharges between water/air interface and a rod electrode is also shown. The results of the investigations provide a better understanding of the approach to calculate the field inhomogeneity factor.