interesting!

I'd like to see more on calculating these distances. Much seems to depend on the bolted fault current, which is often unspecified or ill specified.

Is there a way to safely baseline this in the absense of data from the power company?

Are there regulations covering working alone in these conditions? I checked out the AVO article, it is pretty comprehensive except for the issue of working alone and environmental conditions such as dust, moisture, ect. My Father was ordered to inspect medium voltage switchgear cabinets alone,in dusty conditions, he refused. Was he wrong? This scenerio took place in a major auto manufacturing plant.

A lot of these distances can be meaningless if lightning hits a wire, travels down the wire, and then jumps to you.

During the drought in the summer of 1987 a roofing supply house based southeast of Akron, Ohio parked one of their conveyor trucks in a residential driveway a more than safe distance from an Ohio Edison 69,000 volt transmission line. They then put the conveyor on the roof of the house and started putting roofinf supplies up on the roof.

While they were working, clear weather lightning jumped off of the 69 KV line, hit the mast for the conveyor, and incinerated all 4 rear tires of the truck. No one was hurt but it was one heck of a mess!

There were 3 mechanisms at work here:

1. The drought dried up the soil around the ground rods for the overhead ground wire.

2. The dryness caused the wood poles and crossarms to turn into megavoltage insulators.

3. When the winds aloft are moving in 1 direction at 1 altitude and another direction at an adjacent altitude, you have a clear weather version static electricity generator. Essentially, you have a giant Van De Graff generator but without a visible thunderhead.

Sure, some of these rules state that you need to use protective equipment such as hot line blankets or even tape up the bus, but it stands to reason that strange and unusual thing can happen.

Mike Cole mc5w at earthlink dot net