In the case involving the shield wire, was the sheild wire insulated from the tower when the poor fellow was electrocuted?
Yes, the sheild wire should have been insulated, over such a large distance, a sheild wire can pick up a very large induced current, especially at these kinds of voltages. B:
Was it connected to the sheild wire at its other end?
Generally Joe, according to good HV/EHV practice, this wire would be grounded (Earthed) at both ends, with a large Ground Mat, Scott(Bjarney) could say otherwise too. C:
Was there an issue with the apprentice working in the tower?
On what I know Joe, I would never let an Apprentice Line worker, climb a tower, I'm qualified to work up to 66kV, I use the word "qualified" here, because if you aren't used to working with HV or EHV sized Voltages, you might as well just pack up and go home. No job is worth your life!.
Re: Apprentice Electrocuted on a Tower#150187 11/03/0410:09 AM11/03/0410:09 AM
Shield wires for lightning protection on poleline spans are sometimes periodically insulated from other tower metal to limit circulating currents that may occur with multiple ground connections.
Now that is a HUGE, but true statement Bjarney, it does not even have to be an HV system we are talking about here. Circulating currents happen in so many LV systems, not so much because of poor installation, but because of poor design. For a start, you'd think that HV design engineers would listen to those in the field. Nope!.
Re: Apprentice Electrocuted on a Tower#150190 12/01/0404:05 AM12/01/0404:05 AM
Big Jim, I'm not sure how apprentice training in this respect is done in the US, but here in New Zealand, all apprentice Line Mechanics are sent to one of the National Lines Colleges. Here, they teach Line Mechanics the basics of Line work, all the theory and practice required to start out as a trainee. They actually have a whole series of made up Line Networks and Substations, spread over a few acres and they can be dead or livened as the need may be. I would give you a link but most of them can't afford to have Internet sites. However, most of us Line Mechanics have been to these Colleges more than once and I really enjoy the courses. But back to your question, sure it is a Catch 22 situation, but, a lot of this comes down to supervision and knowing exactly what the apprentices skill level and general aptitude is like. And also, with a trainee on site, I'd personally make it known exactly what the work involves and each step of the job, so that there is no confusion whatsoever and no chance that the trainee could be in the wrong place at the wrong time.
Re: Apprentice Electrocuted on a Tower#150192 01/05/0508:28 AM01/05/0508:28 AM
One statement I would like to make Joe and Scott. In no circumstances, would I allow an Apprentice Line-Mechanic under my supervision, to climb a tower, pole or other structure that carried conductors in excess of 400V Phase-Phase, unless they could tell me what the minimum clearance from Live conductors was and also the Flash-over distance, when in proximity to them lines. I was talking to a Line-Mechanic from down South recently and he was of the opinion that Trainee's are thrown into situations that they have no idea how to get out of, should something go wrong. This in my opinion is wrong and the person that wrote the Management Directive that causes this sort of thing, should be kicked with the largest boot in the land!. It's hard enough to get Trainee Line-Mechanics here without killing them a few months into thier time. And that does happen a fair bit here.