What is the top wire in a transmission line?

Electrical
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What is the top wire in a transmission line?

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The top wire of a high voltage (HV) transmission line is known as the ground wire or earth wire. Its primary purpose is to shield live phase conductors from lightning strikes.

Important Knowledge about Ground Wires

  • They are bare conductors composed of galvanized steel, which has excellent mechanical strength.
  • They are supported at the tops of transmission towers and are securely fastened to the ground at each tower.
  • When lightning strikes, the ground wire intercepts the strike before it reaches the current-carrying conductors beneath.
  • Single circuit towers typically feature a single ground wire, however double circuit towers frequently have two.
  • Ground wires don’t carry any current.

In rare conditions, ground cables are also utilized to transmit communication signals.

To summarize, the thin wire at the top of transmission towers serves as a grounded shield wire, protecting power lines from lightning and ensuring dependable electricity transmission over great distances.

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The top wire in a transmission line is typically referred to as the “ground wire” or “shield wire”. Here are its main functions:

  1. Lightning Protection:
  • The ground wire helps protect the transmission line from lightning strikes. It intercepts lightning strikes and safely conducts the high voltage surge into the ground, protecting the conductors below it.
  1. Reducing Electromagnetic Interference:
  • It reduces electromagnetic interference by providing a path to ground for any induced currents from external sources.
  1. Structural Support:
  • In some cases, the ground wire also adds structural support to the transmission line.
  1. Communication Lines:
  • In modern systems, the ground wire might also serve as an optical ground wire (OPGW), which contains fiber optic cables for communication purposes. This allows for data transmission and monitoring of the transmission line’s condition.

By providing these protections and functionalities, the ground wire plays a crucial role in the reliability and safety of high-voltage transmission systems.

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