Why are overhead transmission lines not insulated?

DWQA QuestionsCategory: Switchgear and ProtectionWhy are overhead transmission lines not insulated?
How Engineering Works Staff asked 6 years ago
3 Answers
How Engineering Works Staff answered 6 years ago

Over head transmission lines are not just a simple copper wire but it is actually a combination of aluminium and steel i.eACSR (aluminium conductor steel reinforced) conductors which has steel rods and so the weight of the conductor is already high so that would add up to the weight of the line resulting into intense pressure on towers.

Another reason is that the transmission line is carrying extreme high voltage and it would require a whole lot of thick insulation to absorb the heat produced by such high voltage.

Also the chances of anyone touching then are very less because they are at a decent hieght from ground

And actually the transmission lines are insulated by “air”….yes u might find it surprising but the current and the voltage in the 3 phase of  over head lines are calculated to let the air insulate them. U might find the wires around u insulated that’s because they carry low voltage and they are surrounded by many objects to block the air to insulate them..while in this case they are in open air

Manti answered 6 years ago
  1. It is too costly to insulate these lines. Except in areas where people reside, these transmission lines are not insulated. Imagine using insulation on millions of kms of transmission lines. It isn’t practically viable.
  2. In case of Underground cables, insulation is required so that the live cables don’t touch earth and get shorted. In over head lines, the air naturally insulates the lines and hence there is no need for insulation.
Himanshu answered 6 years ago

Not necessary, bare overhead conductors from other energy carriers is to utilize air as a natural insulation for conductors suspended from towers

  • It adds cost and weight to the cables.
  • Insulation breaks down with exposure to the elements which shortens the life of the wire, and it also traps heat (bare wire stays cooler.)