Re (2): UPS with earth leakage device.
in [Linux Hardware]
|
Prev: UPS with earth leakage device.
Next: mzWJDaYVaQk
From: ArameFarpado on 9 Jan 2010 17:46 Em Sábado 09 Janeiro 2010 22:12, Moe Trin escreveu: > On Sat, 09 Jan 2010n the Usenet newsgroup comp.os.linux.hardware, in > article <4b48cda0$0$270$14726298(a)news.sunsite.dk>, ArameFarpado wrote: > >>>>> How many wires from an electical substation to the trasformer on the >>>>> pole? > >>substation to transformer is residential distribution? since when? > > The terms used in Europe do not match the terms used in the US. Here, > a substation generally means a transformer site where the voltage is > stepped down from the 'cross-country' values (which may be 56KV on up) > to the levels distributed to the neighborhoods (which may be 2300 to > 13200 Volts). in europe: high tension 50000volts 3 phases substation 10000volts 3 phases transformer post 400volts 3 phases and 230volts each to neutral in europe a substation receives about 50000volts and lower them to 10000volts poles for 50000volts http://thumbs.dreamstime.com/thumb_285/1214983055S25Gbh.jpg (see the top wire for discharge of thunder bolts) poles for 10000volts http://www.danshamptons.com/content/danspapers/issue40_2008/images/FR/lipa.jpg (they also have top wires for thunder bolts) > Separate transformers - either on the local pole, or > on the ground - step the voltage down from this distribution value to > the residential values (120/208 or 120/240) and this is distributed to > one to as many as ten houses. These transformers are not called > sub-stations. of course not, they are called here: transformation posts > Cross-country distribution is almost always 3 phase, > but the neighborhood distribution might be single phase as often as > three phase - depends on how crowded the neighborhood is. correct
From: ArameFarpado on 9 Jan 2010 17:58 Em Sábado 09 Janeiro 2010 21:40, Moe Trin escreveu: > >>then every bilding has it's own copper rod, and it's earth does not >>connect with neutral... it's commom to have about 2volts between >>earth and neutral over here. > > That's a European custom - it's not how it's done elsewhere, including > most specifically in North America. The ground and return lead (what > you keep referring to as the 'neutral') MUST BE joined in the > distribution panel. It's a legal requirement here. OK > >>>> a lightning bolt falls in the ground at 6 meters from you and a >>>> cow, you suffer nothing while the cow gets electricuted and >>>> dies... why? > >>you don't know why? > > No one is interested in games. I assume you are thinking that the > legs of the cow are straddling a potential difference, but that is > equally likely for the person. but the man can stand on the electrified place and not get electricuted if he doesn't touch nothing eles, like a bird on a wire. on the other hand, the cow has 2 legs separated about 1 meter from the other 2... right after the falling bolt, the earth absorves the energy and it is dispersed trought the surrounding area, depending on the position of the cow related to the place the bolt hitted, the cow can receive a few thousand volts between it's front legs and rear legs, the shock will cross it's body stopping it's heart... this fenomenon have been seen several times in the country; cows, dunkeys, horses, etc. died in a instant when thunder bolts fall near them. the all point was about earth's electrical potential, witch is not the same everywhere.
From: jellybean stonerfish on 9 Jan 2010 18:34 On Sat, 09 Jan 2010 22:20:12 +0000, ArameFarpado wrote: > you never seen one of these? > http://www.explainthatstuff.com/car_static_strip.jpg > > http://www.made-in-china.com/image/3f2j00lMKTGsLgHhoiM/Reflective-Strip- > Static-Belt-with-Light.jpg > I've seen these, http://upload.wikimedia.org/wikipedia/commons/8/85/ManWearingTinFoilHat.jpg but that doesn't mean one is needed.
From: Bit Twister on 9 Jan 2010 19:09 On Sat, 09 Jan 2010 22:58:08 +0000, ArameFarpado wrote: > but the man can stand on the electrified place and not get electricuted if > he doesn't touch nothing eles, like a bird on a wire. I disagree. I heard about birds being killed when the power line was shorted to ground. Bird, man, or animal are standing upon a conductor (wire, earth). You can model the circuit which shows they are a parallel resistance or resistor if you will. Here R1 would be the wire or earth. R2 would the man,bird,... The + is each foot's connection to earth/wire. R2 .--\/\/\/\--. | | | R1 | ------+--\/\/\/\--+-------- High values of current passing through the conductor R1 (wire, earth) create a difference in potential (voltage) due to the resistance of the conductor R1. When the potential becomes high enough across R1 enough current will flow up their feet/legs and through R2 (their body). Once the current gets high enough in R2's brain/heart death occurs.
From: ArameFarpado on 10 Jan 2010 07:26
Em Domingo 10 Janeiro 2010 00:09, Bit Twister escreveu: > On Sat, 09 Jan 2010 22:58:08 +0000, ArameFarpado wrote: > >> but the man can stand on the electrified place and not get electricuted >> if he doesn't touch nothing eles, like a bird on a wire. > > I disagree. I heard about birds being killed when the power line was > shorted to ground. > > Bird, man, or animal are standing upon a conductor (wire, earth). > > You can model the circuit which shows they are a parallel resistance > or resistor if you will. > > Here R1 would be the wire or earth. R2 would the man,bird,... The + is > each foot's connection to earth/wire. > > R2 > .--\/\/\/\--. > | | > | R1 | > ------+--\/\/\/\--+-------- > > > High values of current passing through the conductor R1 (wire, earth) > create a difference in potential (voltage) due to the resistance of > the conductor R1. > > When the potential becomes high enough across R1 enough current will > flow up their feet/legs and through R2 (their body). Once the current > gets high enough in R2's brain/heart death occurs. for that to work the way you say, the conductor must be highly damage right under the bird/man feet. |