230 KV contact

[dbrown20]

Noticed in the safety meeting section about the 230 KV contact made on Bonneville's line near Seattle. The fire chief locally had made the statement that electricity would jump out and get you 2,3,4,6,8, and 10 feet etc.

This is not a fact. You would think people in that business would endeavor to become a little more educated about such matters.

In fact the working distance for 230 KV is about 5 feet. For 345 about 7 feet. For 765, about 15 feet.

Saw a video once illustrating bringing a crane into contact with a phase of 69. In slow motion the crane would appear to only draw an arc when within about and inch or less away. Conditions of weather vary and will effect this, but I think what people see is the arc made when they move away from the conductor. This long arc at that moment is what people remember and they begin to say it will jump out and get you.

People in the emergency business need to have a little more education in these matters, but I think it becomes hopelessly complicated when you have to bring in voltage recognition of course.

I know you can violate these distances given and get away with it. Have done it accidently a few times. They try and make them with a pretty good fudge factor.

Oh well, just an observation I guess. dbrown20

[scammy]

power companys are so cheap that they are not educating the public any more, Its a shame ; I have talked to fire and police who have no idea of the power in the lines Its all about the money ,,,if you can save 10 bucks on education ,you can give it to a ceo for a bonus,,,,sucks ,,,,,scammy

[BigClive]

Isn't it enough to give a rough rule of thumb figure of 1kV per milimetre (about 16th inch). Or better still round it up to 1/8" per kV (2" per 10kV).

Having played with Jacobs ladders I know it's prety hard to get an arc to jump 1/8th inch per kV. Of course, other factors like a rough cable surface would affect local air ionisation and lower the voltage.

On the other hand, maybe it's good to miseducate people to believe electricity can jump further, since they are likely to give lines a wider berth purely from fear.

[Squizzy]

You could argue that people should be more educated about the safe working distances from lines. But if people think that it is going to jump out and get them so much the better. They are more likely to stay clear of it. As for the emergency services they should be taught more about the safe working distances and being able to identify the differing voltages by looking at the poles/towers and working out the likely maximum voltage and required clearences.....

[BigClive]

The length of the insulators should be a good guide.

[tramp67]

A good rule of thumb taught to me by an engineer for a transmission company (an engineer with common sense) is that you need an air gap of 1/2 the length of the insulator for clearance, safe working distances are obviously much greater than that. Over 50KV, he suggested a quick method for safe working distances (for qualified individuals) would be roughly 4 times insulator length.

[dbrown20]

I remember a method mentioned to me once by an old lineman. It is somewhat reliable I guess. Take the KV and multiply by 10% and add 2 feet.
Using this method then 138 KV by 10% would be 1.38 feet and then add 2 feet. Thus 138 would be 3.38 or about 3 and 1/2 feet. 345 would come to about 5 and 1/2 feet etc. This differs from the earlier distances I posted, which came from the Kurtz book. Theirs are a little further. Another method is when you begin to feel it fuzzing your hand you need to back off. Humidity makes a difference. You can memorize the distances posted by your company I guess. dbrown20

[PSE Lineman]

I got more info on the contact. They are laying a 36 inch natural gas line from the Canadian border to the Oregon border. They weld the 80 foot sections all together that are cribbed up next to the ditch. Then they sling it with a crane and put it in the ditch. When they did that , somewhere the pipe moved upstream or downstream and the load shifted and the boom started bouncing up and down and got into the 230. One of the guys got it 4 miles away. 2 are out of the hospital and 2 are still in. I was told 1 has burns over 70%. Doesn't sound good for him if you ask me. I read nothing about it in the paper after the initial report. They are keeping pretty quiet about it. Now you know as much about this as I do...

[woody]

Dbbrown...yup... what got most of these workers was step-potential. and a BIG ground... a steel pipeline... from a 230kva BPA line under full summer load. That means the sag was LOW. High voltage theory... woody

[Sno10]

230kv phase to phase. Phase to ground voltage would be in the neighborhood of 133kv. I doubt the pipeline workers got phase to phase on that line. With 1 inch per 10kv arc starting distance as a rule of thumb it would be safe to say an arc will start at around 13 inches for 133 kv from phase to ground. It will substain an arc at a farther distance of course but to get it to start arcing you actually have to get a whole lot closer than the minumum approach distance that most lineman work by. Once the arc starts through the air it breaks down the air creating a lower resistance path for the arc to continue. lets say 2 inches per 10kv rule of thumb for arc starting which would be 26 inches which is a big distance for an arc to start up on that voltage. Wonder how close the crane was to the line and why it was that close to begin with? Had to be darn close IMO. A heck of alot closer than the mad for even a qualified person such as a lineman.

Sounds like a nasty accident and hope all involved come out of this with minimal medical problems. But being burned over 70% of your body doesn't sound good.