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Construction of Covered Conductors

Advantages of using Covered Conductors for Electrical Distribution

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At Axis, we are proud every day of the role that we have played and continue to play towards rural electrification projects across the country. Electrification in India, however, is plagued with large Aggregate Technical & Commercial (AT&C) losses that harm the DISCOM’s long-run health and ability to reinvest in rural electrification projects. These DISCOMs have been under severe financial stress for many years with total external debt estimated to reach Rs. 2.6 lakh crore by March 2020 according to the credit rating agency CRISIL (citation: https://economictimes.indiatimes.com/industry/energy/power/in-support-of-uday-scheme-power-secretary-backs-discoms-blames-regulators-for-debt/articleshow/69298453.cms) but they have also gotten some relief through a 90,000 crore lifeline to fight the Covid-19 crisis.

Innovative technologies such as Smart Meters and AB Cables aim to reduce AT&C losses for Indian utilities. Another innovative technology is Covered Conductors that are used for applications up to 132kV.

 

What are the risks of using Bare Conductors?

Risks of using Bare Conductors

 

 

 

 

 

In distribution networks, the power lines transmit power from one location to another through distribution poles which are situated at the side of roads or on hilly areas. In storm-prone locations throughout India, trees often fall on bare conductor distribution lines causing the pole to fall onto the ground.  Due to the contact between bare conductor & the ground, an earth fault would be caused but the earth's fault will not get cleared due to the high resistance path. The current flow through the high resistance path will cause heating thus resulting in a fire.

 

 

There are additional risks with using Bare Conductors for power distribution:

  1. Lines are forced to shut down due to fallen trees, high wind, and other natural causes which have an adverse effect on revenue generation for the utility.
  2. Fire risk to the forest or structures surrounding the bare conductor.
  3. Risk of electrical injury to birds, animals, and humans.

 

Why should DISCOM’s use Covered Conductors?

overhead line conductors

To overcome these risks, overhead line conductors provided with an insulating cover have been developed & these are known as Covered Conductor. The main advantage of Covered Conductor over bare overhead & underground lines is their increased safety and lower cost. DISCOM’s are increasingly moving to Covered Conductors to ensure reliable power distribution. In comparison with insulated conductors, this covering has reduced thickness but is sufficient to withstand the phase‐to‐earth voltage temporarily.

 

Construction of Covered Conductors

Covered Conductor with one, two, or three sheaths are used for voltages up to 33kV. As we go towards higher voltages, up to 132kV, the number of sheaths increases to five. The most commonly used sheath materials are XLPE and HDPE. The internal conductor can be one of several materials including:

  • High Conductivity Copper
  • Aluminium
  • Aluminium Conductor Steel-Reinforced cable (ACSR)

ACSR is used to achieve a balance between strength and conductivity.

XLPE is also used for AB Cables and is preferred to HDPE since its environmental stress crack resistance is about 20x the and its impact and tensile strength is about 5x as compared to HDPE insulation.

Construction of Covered Conductors

Advantages of Covered Conductors

When compared to Bare Conductors,

  • Enhanced DISCOM revenues through reduced faults and downtime caused by falling trees.
  • Reduced phase to phase clearance, making construction and right of way easier.
  • Reduced clearance from trees or buildings, making construction easier.
  • Reduced risk of forest fires.
  • Reduced faults due to animals.
  • Reduced maintenance cost due to tree maintenance.
  • Reduced risk of human tampering.
  • Reduced risk of corrosion of the internal conductor.
  • Reduced risk of human electrocution.

Covered Conductors should be used in:

  1. Highly Forested areas
  2. Storm Prone areas.
  3. Congested urban areas.
  4. Hot, cold, or intense sunlight.
  5. Wet environments.

 

The XLPE insulation of Covered Conductors provides a great barrier to protect the conductor from environmental factors. You can read our blog here about the “Lifespan of ABC Lines in Moist/Wet Environments”.

Axis is a leading manufacturer of accessories used in low and mid voltage electrical distribution. You can click here to find out more about our range of AB Cable Accessories or contact us for more information on our range of products for Covered Conductors.

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