| Insulator surfaces exposed to tangential electric fields frequently constitute the weakest part of high voltage systems. Although a large body of experimental data on surface flashover has been accumulated and in spite of the fact that the breakdown of gas gaps has become a rather well understood phenomenon, a comprehensive physical understanding of ice surface discharge has not yet been achieved.; This project aimed at investigating further, with new measurements, the basic physical processes of ice surface discharge inception and propagation. The better understanding of these processes will enable to design equipments more adapted to cold regions weather and to increase the power networks reliability in icing atmospheric conditions.; Ultra high-speed photographic techniques have been applied to observe the first nanoseconds of visible discharge initiation and development on the ice surface. Since outdoors insulators have a very complex shape, a simplified physical model of rod-plane configuration has been used. The electric field inception of streamers, their propagation speed and the axial distance of critical volume have been studied.; The results have been derived from Peek's experimental law and compared with those obtained in air gaps. They showed that the presence of ice surface could modify considerably corona streamers inception and propagation parameters. Several hypotheses that could be related to the ice surface discharge inception and propagation have been retained. It's possible that the interaction between the discharge and the ice surface lets occur others mechanisms not existing in air case. Charges accretion hypothesis on the ice surface has seemed to be very pertinent. The presence of these surface charges can modify considerably the local field distribution and it distorts the discharge inception and propagation parameters. Several mechanisms related to the surface charge accretion processes have also been identified. |
