Question about shield wires on power lines....?

Question

Most power lines of voltage ranging from 34.5 - 500kv have shield wires on the tops to protect the primary lines from lightning faults. However, I notice that most power lines in the distribution class (4.16-34.5kv) don't have shield wires. It seems to me that most distribution lines should also have shield wires too but most don't. Why don't they? I'm curious about the reason...?

Answer 1

probably cost.

gotta be 50 times or more distribution lines to transmission lines. helluva lot of copper or aluminum.  

Answer 2

Distribution power lines in lightning prone areas often use arresters instead of static wires based on cost and performance.

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 3

There might not be enough space for the shield wires above the 4.16-34.5Kv lines. Lightning arresters at the electric substations may be sufficient to protect the power system.