Why don't all power lines have shield wires to protect them against lightning?

Question

Shield wires ground lightning strikes thus preventing outages from lightning strikes and I think it's more effective then expensive lightning arresters.

Answer 1

Basically, all telephone poles, for example, have

have a heavy ground wire that runs

from the top of the pole into the earth.

Your home Main junction box neutral wire is also

grounded. Helps, but not perfect.

Answer 2

Usually its the higher voltage, hence higher up lines that have it so I expect they have more chance of being hit.

Certainly its an expense the power companies will try to avoid if it is not going to do much since the lines are lower than surrounding trees, building etc that would get hit first.

Answer 3

i have no clue. they're probably really expensive...

xD

Answer 4

Overhead transmission lines nearly always have shield wires.  These are the thin wires at the top of lattice towers, poles, and pylons.  The "static wires" do not have insulators where the wires are attached to the structure.

Distribution power lines in lightning prone areas often use arresters instead of static wires.  In addition to the cost of the static wires, extra pole height (usually 5+ feet) is needed to maintain proper clearance.

Static wires only protect against a direct lightning strike.  Nearby lightning strikes can induce over-voltage on the power lines and damage equipment even thought the wire itself was not hit.  Installing MOV arresters on all three phases has proven to provide much better protection for distribution circuits.

Answer 5

Shielding will not stop lightning, it would take something very significant to stop lightning. We're talking about millions of volts here, enough to ionise paths of air several MILES long, and air is a very good insulator.

The highest maintained voltage us puny humans have managed so far is 800 KV max, and then we start running into difficulties with switches and break down voltages of insulators.

http://en.wikipedia.org/wiki/HVDC

http://en.wikipedia.org/wiki/Breakdown_v...