 Re: Sad news from the tree industry.. :-(
Very sad.
Apparently the boom was insulated but booms are only insulated on the last stick to the bucket. So if the lower boom contacts truck is live.
Also, I was hunting around on the net and discovered many buckets are insulated ... as in the bucket only. So again in that instance the truck is live.
This also shows what "step potential" is all about. As the ground around the truck is energized and that "voltage" decreases the further you get from the truck due to resistance in the soil it means if you walk away where one foot is placed could be 10Kv and where your next step is could be 5Kv and hence you bridge the gap for electricity to pass through you rather than the ground. Training says hop away or two feet together shuffle.
I doubt the man had a chance, just copped the full load especially if he was touching the truck.
Seems the "trick" for insulated boom trucks is to insulate where the boom meets the chasis. Also I have been thinking that like grounding lines that perhaps the trucks need to drive in a grounding rod somehow say right beneath the truck so if energized the current is grounded away from the outriggers and tyres.
Sad loss, condolences to the family, and there's too many of these which means the current towers need to be improved upon.
Of course, there's limits, like how much voltage can insulation keep away ... wires go up to 330Kv here outback but they tend to clear fell everything around so there's a 100m wide corridor. |