Preventing electrocution from fallen overhead line on a vehicle

[kwired]

I would really doubt that the tires would let enough current flow through the metal parts of the bus as to have enough voltage drop to cause a shock hazard due to a voltage gradient within the bus.

might help to know what other conditions applied. Maybe more then one conductor contacted the bus? Or bus was grounded via more then just through the tires?

 

[Sahib]

Propose all you want, getting it done is another.

Quite true. Getting it done is quite another matter. Just trying to get a grasp of electrical phenomenon involved.

How often to these types of incidences occur?

Infrequent.

 

[Sahib]

I would really doubt that the tires would let enough current flow through the metal parts of the bus as to have enough voltage drop to cause a shock hazard due to a voltage gradient within the bus.

might help to know what other conditions applied. Maybe more then one conductor contacted the bus? Or bus was grounded via more then just through the tires?

I think, even though the bus rubber tires would not let enough current through the metal parts of the bus, the existence of 'poor joints' in the metal parts of the bus might have enough voltage drop to cause a shock hazard within the bus.

 

[iwire]

I think, even though the bus rubber tires would not let enough current through the metal parts of the bus, the existence of 'poor joints' in the metal parts of the bus might have enough voltage drop to cause a shock hazard within the bus.

You can't have voltage drop without current.

 

[Sahib]

You can't have voltage drop without current.

Even with little current?

 

[mgookin]

From the link in the OP "...Kumar said the uninsulated wire got entangled in the overhead luggage rack, exposing the passengers to thousands of volts of electric current..."

 

[Sahib]

might help to know what other conditions applied. Or bus was grounded via more then just through the tires?

Yes. You might be correct. There would have to be a flash over, probably along the tires, to force a fatal enough current through those unlucky passengers to account for Don's observation.

 

[mgookin]

I'm leaning towards multiple points of contact wrapped up in that luggage rack. We normally are dealing with a single point of contact such as a boom (tv news crew, crane, etc.) or a low hanging conductor.

 

[fmtjfw]

How birds can stand on primary. Then, we tend to feel dispersed current less than localized current.
You feel the static if your finger tip arcs over to your car, but if you grasp your key, then touch the car, you don't feel it much.

If it hasn't arced on the rim, then it probably won't arc over a step stool.

Birds don't land on any conductor energized at 22kV or above.

 

[fmtjfw]

It is also possible that the bus did not have a continuous metallic body. A wooden body with discontinuous metal parts may have been the problem.

 

[Electric-Light]

It is also possible that the bus did not have a continuous metallic body. A wooden body with discontinuous metal parts may have been the problem.

highly lkely

 

[don_resqcapt19]

Birds don't land on any conductor energized at 22kV or above.

Is that because of the electric field or the high operating temperature of the conductors? It is not unusual for transmission lines to operate close to 100?C. Not sure about distribution lines.

 

[GoldDigger]

Is that because of the electric field or the high operating temperature of the conductors? It is not unusual for transmission lines to operate close to 100?C. Not sure about distribution lines.

It is primarily the electric field.
If you watch linemen in Faraday suits approaching a line via helicopter you will see that corona effects occur six feet and more away from the line.
Either the current through the body and wings caused by the "no-touch" potential or the ionized air would warn the birds away.

 

[Sahib]

If you watch linemen in Faraday suits approaching a line via helicopter you will see that corona effects occur six feet and more away from the line.

Closer may be the grounded shield wires running along with the power lines. Why such a dramatic corona effect does not take place with the shield wires or with the supporting tower?

 

[GoldDigger]

Closer may be the grounded shield wires running along with the power lines. Why such a dramatic corona effect does not take place with the shield wires or with the supporting tower?

1. The distance to the shield wires, if present, will increase with the system voltage.
2. Coronal discharge happens more readily in the presence of sharp points to increase the local electric field strength. With no other objects around, the conductors and shield wires are maintained to avoid sharp points.

 

[Edward-BSC]

What is the lesson indeed, perhaps the spelling of the word electricity?

What is the lesson indeed, perhaps the spelling of the word electricity?

Do you understand how electrcity works?



I guess not.

Fairly rude considering you are a moderator...

 

[gadfly56]

Just two days before, a bus carrying many passengers came in contact with a 11 kV overhead line in Rajasthan State, India. At least 16 passengers were killed and many were injured due to arcing. The news is below
http://www.naharnet.com/stories/en/181894
It is apparent that a current was established through those unfortunate passengers, while passing from the bus to the ground despite the fact that the bus was having rubber tyres.
There was at least one incident reported in the Readers Digest in which a truck also came into contact with a MV overhead line. But the people inside it were not injured, even when there was arcing from the truck to the ground.
So what is the safety lesson?

It isn't clear from the story, but were the fatalities and injuries sustained while the passengers remained in the vehicle or as they tried to exit?

 

[Sahib]

It isn't clear from the story, but were the fatalities and injuries sustained while the passengers remained in the vehicle or as they tried to exit?

The former is more probable because relatively large number of people died and also people seeing others dying on exit from the bus would have stopped doing so by instinct.