Power Line failure

ok, being a guy who works with vehicle wiring harnesses these windstorms got me curious. How exactly do power lines “go down” in a storm? Is it assembly defects? conductor stress, or what?

I don’t know how often assembly defects come into play, but usually it’s more likely to be something like a tree branch blew into the lines or an old pole split from the stress, or a pole got knocked over by someone who went out of control during the storm and hit it.

Sometimes the wind will blow the lines together, causing a line to line short. The power system uses automatic reclosers to try and fix the fault just because of temporary faults like this. Usually they are set to retry after something like 3 seconds, then 10, then 1 minute, then they give up. If your power blinks out for a couple of seconds then comes back on then chances are you had one of these types of faults. Sometimes you’ll see your lights flash briefly as the recloser tries to reconnect the circuit, but then the fault is still present so they go right back out again.

Probably just a poor choice of words on your part, but the reclosers don’t try to fix a fault, they just try to see if the fault has cleared on its own. I think you knew that, though.

I’m referring to the phyical lines that fall into the road on their own accord. (Not my accord, I drive a toyota)

There are multiple ways that high voltage lines are connected to insulators: some are clamped, but what I’ve seen the most of are aluminum wires wrapped around the conductor to “tie” it to the insulator (aka the ‘bell’)–kinda like wrapping a twist tie around a plastic bag. It’s possible that tension on the line causes the “twisty-tie” to come loose enough that it slips off the insulator. . .

I’m not a linesman, but I play one on TV.

Here in Minnesota, a common cause of downed power lines is ice building up on exposed lines until the weight breaks the line. (And strong winds make it worse.) Takes special weather conditions to do this, though, since they allowed for a certain weight when installing the line. Usually warmer weather followed by a cold snap.

The other common cause is something (usually tree branches) falling on the lines and breaking them.

In strong wings, I’ve heard power lines ‘cracking’ like a whip, presumably they’re blown until they’re extremely tight, and then spring back at great speed. I guess in some situations this could bring them loose at one end.

(and no, the sound isn’t from them shorting, because I’ve heard it on single-wire telephone cables as well)