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What kind of insulators are used for overhead lines?

Apr 07, 2021

   What kind of insulators are used for overhead lines? The advantages and disadvantages of using porcelain crossarms for overhead lines:


   At present, the high and low voltage lines in many countries mostly use porcelain crossarms, which are also widely used in my country. On 6~10kV lines, conical porcelain crossarms are generally used. Porcelain cross arm has the following advantages:


  (2) Both the insulation level and the lightning resistance level are high, the natural cleaning effect is good, and the accident rate is also low. It is more reliable than pin insulators when used in polluted areas.


  (3) Since the porcelain cross arm is relatively light, it is easy to clean, which is convenient for construction, maintenance and live working.


  (4) Since the porcelain cross arm can automatically deflect a certain angle, in case of wire breakage, the wire can be loosened by itself to prevent the expansion of the accident. The main disadvantage of the porcelain cross arm is that the mechanical strength is lower than that of the iron cross arm, and it is easy to be damaged or broken during construction and transportation. Therefore, it is used more in places with sparsely populated people. If its strength is increased, or its material is further improved, the porcelain cross arm will be further promoted and applied.


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  The effect of making the surface of the high voltage insulator into a corrugated shape


   high-voltage insulator surface made of convex and concave ripples can cause the following effects:


  (1) The arc-climbing length is extended. Within the same effective height, the arc-climbing distance is increased, and each ripple can block the arc and increase the sliding flashover voltage of the insulator.


  (2) In heavy rain, the sewage washed by heavy rain cannot flow directly from the upper part of the insulator to the lower part to form a water column and cause a grounding short circuit. The ripples on the insulator play a role in blocking the water flow.


  (3) When the dirt falls on the insulator, the uneven distribution of the convex and concave parts of the insulator, so the insulator's compressive strength is guaranteed to a certain extent.


The insulator on the terminal pole of the overhead line is more likely to be damaged. The insulator on the terminal pole is located at the end of the line. When the lightning wave strikes, it will reflect on the terminal pole, and the insulator on the linear pole will be twice the lightning voltage in the worst case. The voltage side withstand is less than this voltage value, so the probability of damage to the insulator on the terminal rod is higher.


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