Ground currents associated with trees on power lines

[SouthSoundTree]

Anybody have any information about ground currents associated with trees hitting power lines.

We have to do some removals near powerlines, outside of MAD, and am curious about any information regarding this.

Sometimes (ya sometimes) management higher up doesn't really understand what we are up against. Case in point, we were asked to fell a dead old growth doug fir in a laminated root disease pocket parallel to some powerlines, perpendicular to the lean (leaning toward the lines). We told him that we wouldn't fell it 90 to the lean because if it broke off, on to the lines it would go. We could jack it over opposite to the lean away from the wires, but there were other old growth trees in the way, so we couldn't do it.

Later he asked if we took down the dead one. Which part didn't he understand????

It would be good to have some anecdotal or quantitative information to back up our position.

Thanks.

 

[tophopper]

I dont understand the question. Are you talking about step potential?

 

[lumberjack]

You're talking about current travelling back down the spar and into the ground near the cutter being a concern for safety, right?

 

[tophopper]

uuuuuhhhhhh.........step potential?

 

[SouthSoundTree]

Carl had it. Is that called 'step potential', Top?

 

[lumberjack]

Yes, that's called step potential, although the risk to the current travelling back down the trunk and making a difference to the cutter is next to nothing.

What about knocking the lines down (expense) and them hitting the cutter (risk). You're trying to justify why hitting the lines is a bad idea? That sounds odd.

 

[tophopper]

Step potential is the voltage between the feet of a person standing near an energized grounded object.

More common than your scenario, a bucket truck makes contact with overhead conductors and the ground surrounding the truck can / may be energized.

 

[tophopper]

I would think a cutter in this situation could "set up the hinge" and be well clear of the area before the tree started going over?

 

[NeTree]

You bet your ass the tree can energize the ground. Depending on voltage and how green the tree is could only a feet feet... or up to 20 feet.

 

[tophopper]

If there are other trees opposite the lean, couldnt you run a rope from one of those trees to the tree be felled and still drop it parallel the lines with the rope "guying" it away from the wires during the fell?

 

[SouthSoundTree]

The tree is about 40' from the lines, so if we were to attempt to fell it away from the lines and things went south, we would be well clear of being hit by the lines.

The expense of knocking the lines down would be an acceptable risk. The tree is very likely okay to fell opposite the lean. We'd drill/ resistograph the tree to look for shell thickness before thinking of jacking it over. Otherwise, we (I) would likely climb it an hang a 1/2" amsteel or cable and pull with our skidder winch.

My real concern is getting electrocuted by a electricity coming down the tree, through the stump, and into the ground. People get electrocuted by lightning this way. My ex-girlfriend was caught in a lightning storm in Outward Bound. They assumed the lightning position, crouched on a foam pad on the balls of their feet, feet touching. They had to chisel their shoes from their pad after a nearby ground strike.

 

[Al Smith]

FWIW 34.5 kv can burn a cross arm right off a pole .You flip a tree into it something is going to be on fire .

 

[SouthSoundTree]

I would think a cutter in this situation could "set up the hinge" and be well clear of the area before the tree started going over?

I don't follow, we would have the hinge set up, and be jacking the tree at the base. The problem would occur if the hinge failed before the COG is away from the lines' direction/ the original lean.

 

[SouthSoundTree]

FWIW 34.5 kv can burn a cross arm right off a pole .You flip a tree into it something is going to be on fire .

Appreciated info.
Around here, this time of year, a wild fire starting is no real concern. Being electrocuted is the only thing I'm concerned about here.

 

[tophopper]

A lightning strike is a whole nother beast............

can you not make the face cut, and backcut and get the hell outta there before pull is applied. If your that concerned about it, the last thing i would wanna do would be jacking it over.

 

[tophopper]

I don't follow, we would have the hinge set up, and be jacking the tree at the base. The problem would occur if the hinge failed before the COG is away from the lines' direction/ the original lean.

So then guy it back during the drop like i mentioned above...........

 

[SouthSoundTree]

If there are other trees opposite the lean, couldnt you run a rope from one of those trees to the tree be felled and still drop it parallel the lines with the rope "guying" it away from the wires during the fell?

These other OG trees are also dying from laminated root disease. They could get pulled over, but more likely, we would snap the rope.

 

[SouthSoundTree]

From what I'm told, PUD had dropped the lines before to drop trees across the road (park property on both sides).

 

[tophopper]

FWIW 34.5 kv can burn a cross arm right off a pole .You flip a tree into it something is going to be on fire .

Not necessarily Al, it may eventually catch fire, but electrocution will occur immediately upon contact, direct or indirect.

 

[NeTree]

I can't freaking believe I'm gonna say this...

But this is one of those rare times where a hinged snap-cut would be the bomb. You know who uses that, right?

 

[tophopper]

From what I'm told, PUD had dropped the lines before to drop trees across the road (park property on both sides).

That's the best and safest option.




You're concerned you'l snap the rope?...............you just said you'd hang some amsteel or cable and pull it over opposite the lean. Wouldnt that also snap the rope? I must be missing something.

 

[tophopper]

I can't freaking believe I'm gonna say this...

But this is one of those rare times where a hinged snap-cut would be the bomb. You know who uses that, right?

Bow down to the Murph! lol

 

[SouthSoundTree]

Top,

We wouldn't be pulling and jacking it. One or the other. If its solid enough to jack over, after felling the other two dying OG trees in the way, we wouldn't have to climb it to hang a line. If we hang a line, we'd just pull it over with a slight pretension to set the hinge, then clear out of there before the pull.

The techniques for getting it on the ground aren't an issue. Defending our position against a micromanaging supervisor that doesn't understand the techniques or the electrical danger are.

Thanks anyhow.

 

[SouthSoundTree]

I can't freaking believe I'm gonna say this...

But this is one of those rare times where a hinged snap-cut would be the bomb. You know who uses that, right?

Are you just stirring the pot??

 

[tophopper]

Sorry, thought your were looking for solutions.

Ok then...............yes the ground can become energized around the energized and grounded object.