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Why should UHV overhead transmission lines use expanded diameter conductors

  • Categories:Industry News
  • Author:
  • Origin:www.btqdl.cn
  • Time of issue:2020-07-13 10:09
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(Summary description)For overhead transmission lines, in addition to the active loss of wire resistance, there are corona loss and active loss caused by leakage along the insulator; for cable lines, it is mainly dielectric loss.

Why should UHV overhead transmission lines use expanded diameter conductors

(Summary description)For overhead transmission lines, in addition to the active loss of wire resistance, there are corona loss and active loss caused by leakage along the insulator; for cable lines, it is mainly dielectric loss.

  • Categories:Industry News
  • Author:
  • Origin:www.btqdl.cn
  • Time of issue:2020-07-13 10:09
  • Views:
Information

For overhead transmission lines, in addition to the active loss of wire resistance, there are corona loss and active loss caused by leakage along the insulator; for cable lines, it is mainly dielectric loss.

Generally, in the overhead line, the active power loss caused by the leakage current of the insulator is extremely small and can be ignored. Therefore, the corona loss is mainly considered for the overhead line.

Because the insulating medium of the overhead line is air, when the electric field strength on the surface of the wire exceeds the pressure resistance of the air, the air layer will be released to form a discharge, and the movement of charged ions in the air will constitute a corona current. At this moment, we can hear the discharge sound of "Zizi", and can smell the odor of ozone (O3) after the oxygen molecules are dissociated, and light blue fluorescence can be seen around the wire at night. This phenomenon is called For "corona". Corona not only produces active power loss, but also interferes with radio and high-frequency communications.

The generation of corona is mainly related to the transmission voltage. As the voltage increases, the corona usually starts to discharge from the part with greater electric field strength (the sharp corner is not smooth), which is called the initial corona. (The critical intensity of the initial corona is 30 kV/cm). A visible corona then appeared and expanded to the entire surface, forming a full-scale corona.

In order to reduce the corona loss, especially to reduce the interference to radio and high-frequency communication, try to avoid the occurrence of corona. The way to avoid corona is to increase the critical voltage of line corona to make it higher than the line operating voltage. For this reason, the distance between the wires and the wire radius must be increased. However, if the distance between the lines is increased, the construction cost of the line tower will be increased, and the impact on the critical voltage will be slight. therefore. Enlarging the wire radius is an effective way to increase the critical voltage. Therefore, in UHV transmission lines, expanded diameter wires or split wires are used (the equivalent radius of the split wires plays a role in diameter expansion).

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