>From: Tal <.....talKILLspam.....ZAPTA.COM>
>Reply-To: pic microcontroller discussion list <EraseMEPICLISTspam_OUTTakeThisOuTMITVMA.MIT.EDU>
>To: PICLISTspam_OUTMITVMA.MIT.EDU
>Subject: Re: [OT] Saftey issues: AC vs DC
>Date: Sat, 26 Apr 2003 10:49:57 -0700
>
>The main problem with DC is that it is difficult increase/decrease its
>voltage and therefore, it cannot be transmitted efficiently over long
>lines (the old Edison vs Westinghouse debate
>http://www.raintaxi.com/online/1997fall/bloodvolts.shtml). AC allows you
>to transfer the same amount of electrical power with less loses on the
>wires(high voltage, low current).
>
>There are special cases when high power DC system are used (e.g.
>conventional submarines with huge banks of batteries and voltages in the
>range of hundreds of volts) but I don't think any country uses DC for
>power transmission.
>
>As for danger, I think that if you compare DC and AC of the same voltage
>rating, AC is more dangerous because the actual momentary voltage can go
>higher than the DC. This is because the AC voltage rating is typically
>done by RMS which is kind of a average and is lower than the max peak
>voltage.
>
>Hope this helps,
>
>Tal
>

> The main problem with DC is that it is difficult increase/decrease its
> voltage and therefore, it cannot be transmitted efficiently over long
> lines (the old Edison vs Westinghouse debate
> http://www.raintaxi.com/online/1997fall/bloodvolts.shtml). AC allows you
> to transfer the same amount of electrical power with less loses on the
> wires(high voltage, low current).
>
> There are special cases when high power DC system are used (e.g.
> conventional submarines with huge banks of batteries and voltages in the
> range of hundreds of volts) but I don't think any country uses DC for
> power transmission.
>
> As for danger, I think that if you compare DC and AC of the same voltage
> rating, AC is more dangerous because the actual momentary voltage can go
> higher than the DC. This is because the AC voltage rating is typically
> done by RMS which is kind of a average and is lower than the max peak
> voltage.
>
> Hope this helps,
>
> Tal
>

> DC is used for very high voltage (1 MVolt+!) long distance power
> transmission. For one thing, it avoids the skin effect.
>
> Bob Ammerman
> RAm Systems
>
> ----- Original Message -----
> From: "Tal" <RemoveMEtalKILLspamZAPTA.COM>
> To: <PICLISTSTOPspamspam_OUTMITVMA.MIT.EDU>
> Sent: Saturday, April 26, 2003 1:49 PM
> Subject: Re: [OT] Saftey issues: AC vs DC
>
> > The main problem with DC is that it is difficult increase/decrease its
> > voltage and therefore, it cannot be transmitted efficiently over long
> > lines (the old Edison vs Westinghouse debate
> > http://www.raintaxi.com/online/1997fall/bloodvolts.shtml). AC allows you
> > to transfer the same amount of electrical power with less loses on the
> > wires(high voltage, low current).
> >
> > There are special cases when high power DC system are used (e.g.
> > conventional submarines with huge banks of batteries and voltages in the
> > range of hundreds of volts) but I don't think any country uses DC for
> > power transmission.
> >
> > As for danger, I think that if you compare DC and AC of the same voltage
> > rating, AC is more dangerous because the actual momentary voltage can go
> > higher than the DC. This is because the AC voltage rating is typically
> > done by RMS which is kind of a average and is lower than the max peak
> > voltage.
> >
> > Hope this helps,
> >
> > Tal
> >

> -----Original Message-----
> From: Herbert Graf [SMTP:@spam@mailinglist@spam@spam_OUTFARCITE.NET]
> Sent: Sunday, April 27, 2003 11:36 PM
> To:   spamBeGonePICLISTKILLspamMITVMA.MIT.EDU
> Subject:      Re: [OT] Saftey issues: AC vs DC
>
> > Mike Singer <.....msingerspam_OUTPOLUOSTROV.NET> wrote:
> > > Bob Ammerman wrote:
> > > > DC is used for very high voltage (1 MVolt+!) long
> > > > distance power transmission. For one thing, it
> > > > avoids the skin effect.
> > >
> > > Could you, please, estimate the depth of a skin
> > > effect in copper lines at 60Hz AC.
> >
> > http://www.circuitcellar.com/library/eq/153/3.htm
>
>         Thanks, I didn't feel like pulling out my E&M text... :) 20mm?
> Wow, that's
> worse then I thought, I thought at least an inch. TTYL
>
>

> -----Original Message-----
> From: pic microcontroller discussion list
> [.....PICLISTRemoveMEMITVMA.MIT.EDU]On Behalf Of Brendan Moran
> Sent: Wednesday, 25 June 2003 2:49 PM
> To: RemoveMEPICLISTspamBeGoneMITVMA.MIT.EDU
> Subject: Re: [OT] Saftey issues: AC vs DC
>
>
> >AFAIK AC can not be used for very long lines, for instance in Sweden
> >between the power generation (in middle and north of the country) and
> >the use (mainly in the south).
>
> It is my firm belief that that is inaccurate.  In British
> Columbia, Canada,
> there is a large scale power generation facility called the WAC
> Bennett Dam
> (2.73MVA generating capacity).  The eventual destination of the
> majority of
> this power is the Greater Vancouver area.  This destination is
> approximately 770km away from the dam at the closest point.  This power
> also runs the length and breadth of Alberta and British Columbia.  On top
> of that, due to the California Energy crisis, BC Hydro (the owner of the
> WAC Bennett Dam) is selling power to the state of California.
> That is 1500
> km from the generating station.  It should further be pointed out that the
> entire North West power grid (In North America) runs from southern
> California to at least southern Yukon, which is a combined
> distance of 3300km.
>
> To the best of my knowledge, the entirety of that power grid is
> AC power of
> varying voltages (or at least all the power lines I've seen are 3 wires,
> and the lines leaving the generator are 3 wire.  If they were going to
> convert to DC, I'd expect them to do it at the generating facility rather
> than build a separate facility).  There is one exception to that that I
> know of, which is an SCR switched DC line out to an island in BC.  That is
> a relatively short run and is not along the main power stream,
> but rather a
> branch from it, and there may well be more like it.
>
> So, yes, AC power can go a long way.

> >AFAIK AC can not be used for very long lines, for instance in Sweden
> >between the power generation (in middle and north of the country) and
> >the use (mainly in the south).
>
> It is my firm belief that that is inaccurate.  In British
> Columbia, Canada,
> there is a large scale power generation facility called the WAC
> Bennett Dam
> (2.73MVA generating capacity).  The eventual destination of the
> majority of
> this power is the Greater Vancouver area.  This destination is
> approximately 770km away from the dam at the closest point.  This power
> also runs the length and breadth of Alberta and British Columbia.  On top
> of that, due to the California Energy crisis, BC Hydro (the owner of the
> WAC Bennett Dam) is selling power to the state of California.
> That is 1500
> km from the generating station.  It should further be pointed out that the
> entire North West power grid (In North America) runs from southern
> California to at least southern Yukon, which is a combined
> distance of 3300km.
>
> To the best of my knowledge, the entirety of that power grid is
> AC power of
> varying voltages (or at least all the power lines I've seen are 3 wires,
> and the lines leaving the generator are 3 wire.  If they were going to
> convert to DC, I'd expect them to do it at the generating facility rather
> than build a separate facility).  There is one exception to that that I
> know of, which is an SCR switched DC line out to an island in BC.  That is
> a relatively short run and is not along the main power stream,
> but rather a
> branch from it, and there may well be more like it.
>
> So, yes, AC power can go a long way.

>
> > >AFAIK AC can not be used for very long lines, for instance
> in Sweden
> > >between the power generation (in middle and north of the
> country) and
> > >the use (mainly in the south).
> >
> > It is my firm belief that that is inaccurate.  In British
> Columbia, Canada,
>
> Yes.  Isn't one of the main benefits of AC that it can be
> easily stepped
> up/down -- high voltage for long runs (minimizes the I^2R
> losses), and low
> voltage at the pole to your house...Doing this with DC would be a much
> more difficult job, no?
>