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Ice-covered Dance And Icing Shedding
- Jun 01, 2018 -

    The phenomenon of low frequency and large amplitude self-excited vibration generated by the excitation of wind is caused by the eccentric icing of overhead transmission lines. Generally speaking, when the wind is blown to a non-circular cross section of wire, it produces a certain air force, which induces a low frequency (about 0.1~3 Hz) and a large amplitude self-excited oscillation.

    The galloping of transmission lines usually depends on three factors: uneven icing, wind excitation and line structure parameters. The harm caused by the dance is multifaceted, the light will flashover, the tripping, the heavy damage of the fittings and insulators, the wire breaking, the broken line, the loosening, falling off, and even the tower bolts of the tower, leading to the major power grid accidents. Local sensitive areas that are prone to galloping are mainly located in areas such as draught, open area, river and lake, which are easy to ice and strong in wind excitation. In order to prevent line galloping, installation of interphase spacers, wire clip rotary spacers, double pendulum anti dancer, detuning pendulum, eccentric weight hammer and other anti-dance devices are generally adopted.

     The ground line has low density icing, such as white frost, rime, mixed song, snow and so on. Because of loose bond, it automatically falls off under the action of wind or self-weight, and the tension of the guide line changes suddenly, causing the leaping of the ground line. The uneven ice coating or ice shedding in different stages will cause the difference of tension, and make the ground wire damaged and slid. It will also cause the incline and damage of the line tower to bear the unbalance tension, and the tower accident will occur when it is serious. At the same time, the ice shedding in different stages will cause the discharge of the lead and the ground line jump close to each other, and the wire jump leads to the discharge line of the tensioning tower and the transverse load, and the suspension insulator string is offset by the collision and so on.