Yesterday, I was cutting the lawn and I noticed some commotion out in the street. A tree-trimming company was doing the yearly maintenance of the trees around the power lines. I walked over and saw one of the tree trimming boom trucks had tipped on its side, and the boom was resting on top of the high voltage line.
The outrigger on the truck was down, but due to the recent heavy rains, it sunk right into the ground, and that was enough to tip the truck over. The boom was fully extended at the time due to the fact that the power lines are about 20 feet in from the road.
Anyway, no one was injured, thank God. The high voltage line on my street is insulated (most likely because of the large amount of trees around it), and that is probably what prevented this from being a disaster. At least this story has a happy ending, considering the incredible danger.
I believe that you have understated the possibility of tragedy because most overhead residential primary distribution conductors that do posess some insulation, well...it's not really any real voltage rated level of insulation. I added this link to another post that ended up in the Photo gallery section of this forum, but you might like it as well http://www.themeterguy.com/photogallery/BoomTruckinPowerLines.wmv It's of a crane that had just contacted an overheas primary with it's winch line; pretty dramatic!
I remeber working on a trouble call one winter day, and was going from pole to pole. I was working alone, [ tat was stupid, but the contractor was a jerk, shoulda known better], Crawled into the bucket, raised up about 30', and started to swing to the side. In all the moving of the truck, I forgot to re-set the outriggers that stop. The truck leaned but didn't tip. God!! was I lucky. I quickly twisted grip back and lowered the boom. Then set the outriggers. I probably should have gone home at that point.
Re: Disaster narrowly averted!!#26038 05/28/0310:43 AM05/28/0310:43 AM
What probably saved these guys was the insulation gap that all boom/bucket trucks are required to have. They are to be non-conductive along the boom. There are marks on the boom showing where the insulation begins and ends. We get ours dielectrically tested every year and, hearing stories like this, it's well worth the cost
Mike, yes, I did stick around. Obviously, the power company was summoned and they shut the power off. It required two class-7 size wreckers to pull the truck upright. Fianlly, the linemen from Northeast Utilities had to pull the sag out of the HV and neutral wire. The truck that fell over was towed away, presumably to be inspected and repaired if necessary.
Coreman, good point about the insulation. I was very surprised myself that it wasn't damaged, considering that the boom had pulled the HV line down about 8 or 9 feet from the top position.
Yes, these guys are very lucky. God was smiling on them yesterday indeed.
Paul, I believe the distribution voltage in my neighborhood is 2400, single phase.
HV three phase does run through some residential neighborhoods, for instance, where I used to live, there was a sewage pumping station at the end of my street that obviously required 3 phase. But to see 3-phase on a side street is uncommon unless there is some specific need for it, as I mentioned.