VOLTS

[ebee]

So is 70v dangerous then ?

 

[1974stephen]

Ebee - start with a 9V PP3 battery on your tongue. If you can take that for a few seconds - try moving on to higher voltages. Two car batteries in series perhaps?

 

[Big_Spark]

Also the higher the voltage the more it can "jump" so that is why "overhead lines" are so high up, so they cant jump to you, which is why you should NEVER climb a pylon, because as you get near it the electricity will jump to you and.........say no more.

a typical pylon runs at 33,000 volts although some are higher and some lower . The household supply is only 230v and a battery is only 1.5 v, so you can see the major difference.

Breezer, I would point out, just as an observation, that Pylons are significantly higher than 33kV. Overhead lines on wooden poles will be 11kV, metal pylons up to 10m high will be 33kV, but above 10m in height the lines will be carrying 66kV, or more likely 132kV or higher.

The Grid operates like this.

Generation usually at 23kV, this is stepped up to 400kV for initial tramsmission, this is dropped to 275kV and then this is dropped to 132kV, which in turn is dropped to 33kV for substations serving small neighbourhoods or factory units etc. This is then further dropped to 11kV which is then stepped down to give the LV supplies of 400V/230V.

 

[ban-all-sheds]

i'd say the voltage conversion advantages of AC were so great that it would have won over DC even if AC shocks were more dangerous.

Probably true at ELV & LV, and "regular" HV.

But for very high voltage long distance transmission lines, advances in semiconductor technology have altered the equation, and there is a lot of interest in DC for those applications.

 

[Big_Spark]

DC is generally used for "Interconnectors", systems that link National Grid systems, such as those that link the UK and France, Switzerland and Austria and Italy, France and Germany.

Currently the National Grid is constructing one to connect the grids of Tasmania and the Australia.

The US and Canada have almost identical transmission systems and so they have no DC interconnector, the two grids are simply connected as one, in fact most of the power in the upper East Coast states (New England, New Brunswick, etc) is actually generated by Hydro power in Canada.

Copper losses are less for DC than AC, however untlil the modern era the conversion of DC to AC or vice versa was very inefficient, but as BAS has pointed out, semiconductor technology has helped this process tremendously.

 

[ebee]

How many volts is dangerous?

Did anyone mention AC at 50Hz interferes with heart and brain signals?

 

[ebee]

http://www.llnl.gov/es_and_h/hsm/doc_16.01/doc16-01.html#appb

 

[Biggles..]

From years back i thought city and guilds used to state that lethal voltages were 50v Ac and 120 Dc anything under those were termed as being safe. With this in mind, and i could be wrong in thinking that building sites use 110v and this is classed as a safe voltage all down to the fact about how 110 is generated and that if you get a belt it will only be 55v wrt to earth.

 

[ebee]

Yes but I think that we gotta remember no voltage is really safe hust relatively and we must always bear in mind that they are "rules of thumb " only.
After all 50V in a bathroom no not safe but in normal dry conditions then fairly safe