Vibration of a water droplet on a polymeric insulating material subjected to AC voltage stress

Abstract

The behavior of a water droplet on a silicone rubber plate was observed with a high-speed camera under ac voltage application. It was confirmed that a water droplet vibrated and that a remarkable deformation from the original droplet form occurred at the mechanical resonance frequency. Vibration frequency of an uncharged water droplet was double the frequency of the applied voltage. On the contrary, in the case of an artificially charged droplet, vibration frequency was the same with that of the applied voltage. A macroscopic mechanical model was devised, to which the experimental data were well correlated. Flashover voltage via the water droplet was also measured. Lower flashover voltage was obtained at the mechanical resonance frequency.

Behavior of water droplets on polymeric insulation surfaces under hybrid field stress

“…Figure 10: Oscillation pattern of a 80 μl droplet before pd inception, tangential field orientation, a) AC100, b) AC90, c) AC75, d) AC50, e) AC10; repetitive surface shape every 10 ms for a) and b), for c)-e) every 20 ms After pd inception the droplet changes its shape and starts to oscillate with twice the frequency as before. This is caused by a charging of the droplet due to the pd [10] and by the change of the droplet contact area due to elongation changing the natural droplet oscillation frequency. The surface frequency, however, does not change.…”

“…The surface frequency, however, does not change. The electrostatic force acting on the water droplet is proportional to the square of the electric field [5,10]. In case of an electric field which consists of an AC and a DC component this correlation has to be extended:…”

Assessment of the resistance to tracking of polymers in clean and salt fogs due to flashover arcs and partial discharges degrading conditions on one insulator model

“…One can conclude that surface deteriorations depend on the chemical structure of a material, the conductivity of the sprayed fog and the voltage gradient. Many researchers [48, 49] show that the level of PD inception voltage (PDIV) depends on the oscillating frequency of water droplets, their volume and the material hydrophobicity. Other investigators [50, 51] suggest that the PDIV depends on the frequency/pulsation (20 Hz < f < 100 Hz) according to a logarithmic function and that the increasing of the droplet volume increases the PDIV.…”

Wet conductor surfaces and the onset of corona discharges

“…Dynamic behaviour was also evaluated on the water stream from the bottom of conductors [7][8]. As a result of the development of composite insulators, considerably more work has been published on water droplet behaviour on insulation surfaces [10][11][12][13][14][15][16][17][18][19].…”