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Power Line Icing And Icing Overload
- May 18, 2018 -

      Line icing

Generally in the winter or early spring season, when the air temperature is between -5~0 and the speed of wind is 1~15m/s, the air humidity is over 85%, the cold fog and the rain drops falling to the power line will produce ice on the electric line surface, this is the force line icing. Frozen snowflakes, when passing through a warm layer during the landing, tend to be in a wet and melting state. When they fall on a power line below the freezing point (0 degrees centigrade), it will freeze the white accumulation of ice. When the ice formed by the cold fog we call the rime. We call the glaze when the cold raindrops cover the ice, and when the frozen snow covers the ice we call the rime (also called Shi Xue).

Sometimes there will be an overcooled drop of water that does not use a particle size (both fog and rain). It fluctuate with the air flow. When the collision is on the power line, the part of the water increases. The ice is translucent, often frozen on the windward surface of the power line, which is called a mixed song.

Icing overload

Ice overloading means that the icing will increase the vertical load of the transmission line, such as tower, guide and ground wire, and the horizontal load of the transmission line will increase with the increase of the ice thickness of the windward surface of the wire. Serious icing causes breakage of conductor and ground wire, collapse of tower and damage of fittings.

        When the transmission line is covered with a certain volume and weight, the load of the vertical direction of the transmission line and the ground line is multiplied, the sag increases and the distance of the wire to the ground decreases, thus the flashover accident may occur. When the sag increases, the two wires or wires may collide with the ground under the action of the wind, which can cause a short circuit trip, a burn or even the accident of a wire. If the weight of the ice is further increased, it may exceed the mechanical strength of the wire, the fittings, the insulators and the tower, so that the wire can be pulled out from the pressure nozzle, or the outer aluminum shares are completely broken, and the steel core is drawn out. When the wire overloading exceeds the rated load of the tower, it may cause the tower foundation to sink, tilt or burst, pole tower, and even collapse.