IF A HYDRO LINE COMES DOWN IF YOU PICK IT UP DO YOU GET A SHOCK (THERE IS NO POTENTIAL TO GROUND FROM A LINE TO GROUND).?

a wha???

Technically, if the fault has cleared and the fusing has operated, the wire should by rights be dead.
I wouldn't recommend picking up any fallen power line, mainly because of the fact that the line may have an Auto-Recloser on it and the wire may become live without warning.

A hydro line?? I've never heardof one. What is it?

(Please don't use all CAPS in posts, it makes them difficult to read, and in internet etiquette, is the equivalent of YELLING AT US) Thx ...S

Maybe a Hydro Line is from a Hydroelectric power plant

Hydro in Maine could mean power company. The 2nd biggest POCO in Maine is Bangor Hydro, shortened to just Hydro

Hydro = water. Perhaps you will get wet.

Ya it comes from the term hydro electric Here in ontario Canada we had Ontario Hydro
I think hes talking about gradiant voltage where you get a potential from one foot to the other due to the length or you stride?I had an old Linesman tell me if a kv line drops near you standard practice is to not move but if you must walk heel to toe.

Hydro line = power line, if I'm not mistaken.

I think we have a "Canadian vs American" English situation here.

Furthermore, I believe the question is referring to a line that has fallen and is in contact with the ground--at that point, the line is "grounded", and would one receive a shock if touching it? Again, I think that's what the question is.

Trumpy is right though. Re-closers are commonly used by POCO's. The idea is that a intermittant energizing will burn free whatever is shorting the line, like a tree limb etc.

Above 600 volts, the ‘rules’ change drastically. With contact accidents at this level, the amount of current and path through the human body can readily cause live tissue to be “cooked” from the inside out.

Medium- {and high-}voltage circuits demand a much higher level of care and “respect” and are much less forgiving of accidents.

There is a universal rule dealing with medium {and high} voltage — NOT Grounded: NOT Dead. The seriousness of this issue for routine operations is evidenced in: http://www.hubbellpowersystems.com/powertest/tips_news/pdfs_best/09-9501clamp.pdf




[This message has been edited by Bjarney (edited 01-30-2004).]

Easy answer:

Watch a Medium Voltage Primary Feeder Conductor when it falls off an Insulator and finally reaches the Earth Ground.
It will dance around like crazy - blowing sparks, creating plasma arcs, making all kinds of noise - until something gives out (like Breaker, Fuse, fried wire, etc.).
Then it becomes still - but by no means is it "Dead"!

Of course, Automatic Reclose will occur - resulting in the same crazy-bouncy dance sessions again (and if someone with a death wish grabs the wire, the same will happen to that person!).
But even if the circuit does not get re-energized, there will be discharging from Coupled Reactances, along with the circuit's initial Line / Circuit Charging plus any other stored Reactive Power - all of which, if drawn through a load connection with an Impedance similar to that of living people, will result in a similar crazy dance on that person!

So the answer is:
Yes, you can get shocked very easilly in almost any circumstance.

I know you are only asking this to know, and do not plan on attempting this ever!

If you want to know more about this, let us know!

Just ask the Linepersons here about L-G flows! Things take a drammatic change above 2KV, a really drammatic change above 35KV;... and a mind boggling change above 200KV!

Scott35

Don't even go close to a downed HV or MV line. Step potential!

Just because it's not making sparks on the ground, there is no guarantee the line is dead and even if it is dead, there is no guarantee that it will remain so.

As I understand the original question, you are thinking of an ungrounded system. At first sight, it seems you could get away without getting shocked. But to detect a fault there has to be a current. The utility may to have a resistance ground which allows a small current to flow back to "sound the alarm". You don't want to be part of this circuit. In addition, there are unintentionally grounds along the line. I'm sure Bjarney, Trumpy and Scott35 know more about these things.

sorry for the confusion,i mean a power transmission line that carrys the power from customer to customer(ex:27.6kv).
now if one of these lines comes down and is still alive it being fed from a delta source where there is no potential to ground,then why is it that if you were to grab this that it would kill you,remember that there is only potential phase to phase.

with voltage present, there is potential. whether by design or not. I don't know about HV stuff, but it's like the bird on the wire. bird is at same potential as wire no shock. bird puts one leg on pole, thanksgiving dinner, pre cooked!!

So if somebody grabs the insulated portion of a downed wire, he'll get fried no matter what? Please explain why this occurs.

Another example of operating under different rules than us <600V guys...

Many HV lines are designed with "semi-conductive" insulation. I have no idea how/why, but I've seen it in the product descriptions for the big stuff.

Depending on the voltage of the line you could get nailed and good from a few feet away, without even touching it at all. I'm sure some of the other members could get really technical on it. But voltage will break down the die-electric strengh of most insulating material easily once the path is made. Even the air it self! The average rubber soled shoe, and leather glove is useless above 120/240. Otherwise you should be wearing proper PPE for the voltage.
http://www.corvib-int.com/catalog/index.php?cPath=29_30

And the conductive properties of a dry 2x4 may as well be a copper pipe at +10KV. I'm sure there will be some corrections to what I said, but can not stress enough to stay clear of downed lines of any kind!

 
DougW has a good point about higher-voltage cables. At 2-35kV, the cable dielectric layer is typcially ethylene-propylene rubber or cross-linked polyethylene. [Typcially, 15kV-class, 133% insulation-level cable has a dielectric thickness just under ¼ inch.] Inside (under) the dielectric layer in imitate contact with the center conductor, and over the outside of the dielectric are are two semiconducting layers to even out electric stresses in the dielectric. Over the outer semicon is helically-wrapped copper tape or copper wires that must be solidly grounded as part of limiting electric stress in the dielectric layer. A generic term for this material is shielded polymeric cable.

In the last ~80 years, cable manufacturers have found that the dielectric material has to be of extremely high purity with antiseptic conditions during the extrusion process. Also, field preparations during installation of cable terminations and splices must be performed by a skilled and experienced person in a clean area to limit premature failure. Before energization of the cable, it is routine to apply DC-overpotential testing to reasonably assure that the circuit will have acceptable reliability over expected life of the installation. Workmanship on installation can be proven by good {or rejected} by poor} overpotential-test results.



An MV-cable splice illustration energy.tycoelectronics.com/rrg/raychem_rrg/59.pdf

On the North American continent, the practical upper limit of routinely manufactured extruded-dielectric shielded cable is presently 138kV.

P.S.: Never forget that In all but limited cases, overhead spans are BARE.




[This message has been edited by Bjarney (edited 09-12-2004).]

I e-mailed Joe Tedesco, and said,
'Hey Joe, I think this thread could us a scary video link..."

No video, but sent this poor sole.
(Too greusom to show!) Blown off fingers! Or that video of the guy on angle dust climbing a pole. Ot this one: Ryan posted a while back. http://www.mikeholt.com/documents/mojofiles/BoomTruckinPowerLines.wmv

Jib contact to 69kV, with sheet of concrete turned into a frisbee..

Thanks e57 and Bjarney, great info.

New Information:
If a line falls from a pole to the ground, stay the H*ll away from the darned thing, it will kill you!. GRRR!

Now why don,t these lines short out across rain or snow as these would be a connection to ground at some point?

GETELECTRIC:

with med and high voltage when the cable[s] do fall down and the fuse or recloser will not trip very fast due the ground restance and some case few lines i know of it will not blow the fuse unless get " bolted" or " direct" short then it will trip it.

like example 24 Kv line when it drop and it will keep alive until OCPD go out but the chance it will trip is hard to predict due too many thing around the sisuation there like dry ground it will not trip it at all and very wet ground it might trip but hard to say depending on water itself and when it is wet the chance to get shocked or electruted is greater and of course snow it will stay alive majorty of the time and most poco fuse have very long time delay to blow and i mean very long time to trip depending on how much over current running unless direct short it will trip alot faster

if need more question just drop a line here.

Merci, Marc

Sometimes they do in REALLY extreme circumstances. (all of my line work experiance was <600 in the military and breif, but some of the other guys can eleborate more.)Like a VERY severe driving rain. Even then it would probably be very rare to get a short past all the dry gaps under the insulators. (All those stacked china hats) Epecially with higher voltage it would probably vaporize it before any short. At lower voltage it's probably more common.

I used to live near a beach, and every night the fog would come in heavy. When it did, the HV lines, (Big fat ones, no idea of what voltage they were) would shoot dancing green sparks down the edges and sides of the insulator racks to the ground line on the cross bar. A fairly load steady hissing all night long. Really creepy like something out of a Frankenstien Movie. One night during a storm they shorted during a horizontal down pour. (not sure if it was the wind that pushed the conductors together, or the rain closed the gap) A great explosion and then dark, a second or two before it all came back on. Looked out side and all the lines were steaming!