Thursday, June 11, 2009

Why No Insulated Covering on Overhead wires running through the poles on the streets?

Our household wires all have insulated covering, using rubber, plastic or whatever it is. But the overhead wires running through the poles on the streets do not have any insulated covering. Explain.

It could be a way to save the finances, i guess

Reducing cost and reducing Electrostatic and magnetic coupling.

It's quite unlikely that someone would go up to a height of approximately 25 feet just to touch the wires. Moreover, if anyone touches the wires one would not complete the circuit. So there is least use of insulation.
While repairing, electrical supply is switched off.

The Great Transmission Line Theory
1. The wires running overhead do not have any insulating covering, ya it's absolutely true because in actual they don't need that.

2.Though the voltage carried by them is 230V to 4000V(in HV system), the separation is enough to produce very high impedance in order to avoid any coupling, also as someone said earlier the probability to someone touch that wire is also low.

3.Almost all such wires are made up of Aluminium, the conductor is having property of expansion, now if we put any insulator like Bakelite it may crack due to the expansion.
using rubber may solve the problem but then, the rubber too become hard due to prolong exposure to sunlight.

4. All connections made over such wires are just by warping another wire over them, as in Indian villages, so everytime removing that insulation will not be feasible.

5. Finally to conclude I would like to add... Addition of insulation does not add to the quality of transmission, ya it may prevent energy theft to certain point but the capital cost will be more than that. so the overhead transmission lines are normally not coated with insulation, but as in some crowded places they do cover them with pipes, or some insulation to avoid accidents.

Do You Agree?

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