Whole house "battery" wiring/power...

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The differences, both historical and current are fascinating from either perspective. I've had some extensive discussions with an EE friend over in Manchester and we're both learning something new all the time.
I don't think I've ever asked if there were ever DC rural systems over there. These were off-grid and typically had a bank of lead-acid cells which were charged by gasoline or steam driven generators or windmills. There were 32V versions of virtually every small appliance of the day. Radios, fans, food mixers, etc. They made sense when farmhouses were often miles from the next house and more miles to the nearest town.
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And most farmers were quite happy to tie to the grid when it became possible - helping to build lines as well-- lots of rural electrification co-operatives came into being in the late 40's. My father was involved (from the utility side) with the the first one in Alberta, Canada, and the farmers were more than welcoming. The old windcharger/battery systems worked reasonably well for supplying lighting and small appliances but weren't capable of handling the heavier loads around the farms.
--
Don Kelly
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On Mon, 12 Oct 2009 19:35:40 -0700, Don Kelly wrote:

Interesting stuff. I never knew they had any real off-grid networks; I'd only ever heard of local generation supplying single dwellings. Shame there doesn't seem to be much about all of this on the 'net.

Take out the 'old' and that probably still stands ;)
cheers
Jules
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wrote:

Edison went to great political lengths to discourage AC, even publicly electrocuting animals to show how AC causes heart failure where the equivalent DC voltage would not.
http://en.wikipedia.org/wiki/Topsy_(elephant)
As you know the very nature of DC required multiple grids and an endless supply of local generating plants, all of which Edison wanted to provide.
My relatives have a farm in central IL with a generating windmill, this farm only got on the grid after WW2. In the 1930's windmill manufacturers in the US were producing about 100,000 windmills a year for farms that had no access to electrical grids. It used storage batteries. Funny how the wind circle is now being repeated.
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wrote:

Edison went to great political lengths to discourage AC, even publicly electrocuting animals to show how AC causes heart failure where the equivalent DC voltage would not.
http://en.wikipedia.org/wiki/Topsy_(elephant)
As you know the very nature of DC required multiple grids and an endless supply of local generating plants, all of which Edison wanted to provide.
My relatives have a farm in central IL with a generating windmill, this farm only got on the grid after WW2. In the 1930's windmill manufacturers in the US were producing about 100,000 windmills a year for farms that had no access to electrical grids. It used storage batteries. Funny how the wind circle is now being repeated.
These farmers weren't on any off- grid network. Some had windchargers and some may have had generators but many were still without electricity of any sort. Windmills to pump water, kerosene lamps. and wood or coal for heating. The co-operative effort was to get connected to the grid at a time when there were few, if any, farms remote from towns that did have grid connections. This meant building a local distribution system and the utility providing the tie to the grid and operation of the system. The first case was in a tightly connected Mennonite "colony" and later ones were more general groups of farmers after the success of this one. In general rural (and urban) population densities were (and still are) lower than those in IL(about 1/10 the population in 5 times the area-admittedly mostly concentrated in the lower half (prairie/parkland)of the province ).
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Don Kelly
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SUCH KNOWLEDGE
WHAT A WASTE
I AM PROTEUS
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On Tue, 13 Oct 2009 15:07:49 -0700 (PDT), Proteus IIV
Not within your skull.

Yes, you are very much, a waste.

You are retarded.
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On Tue, 13 Oct 2009 07:59:28 -0700 (PDT), windcrest

But he was wrong, and DC kills as well. Including the onset of ventricular fibrillation.
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wrote:

----- The sensitivity of humans and other mammals, with regard to frequency happens to peak in the 50-60Hz range. Edison took advantage of this and Tesla countered with high frequency, high voltage discharges, saying, in effect, "this is AC, perfectly safe" Both lied (whether they knew it or not and the not was shown much later) with profit as a motive. Other hazards such as arcing at switches or poor contacts, worse with DC, were ignored.
--
Don Kelly
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On Tue, 13 Oct 2009 19:51:24 -0700, Don Kelly wrote:

I recall the breakers at one site I was working at fed compressed air through the breaker upon opening, just to extinguish any arc that may have formed (that was a 400V DC setup) - I think that's typical on higher power DC stuff. The breakers were about the size of a lunchbox.
cheers
Jules
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Jules wrote:

Hi voltage AC breakers still do use compressed air in some. The 'blast' is aimed between the arcing contacts to literally blow out the arc.
Lower voltage DC (up to 350VDC) that we used on submarines just used blow-out coils to create a magnetic field that 'pushed' the arc-conducting gases up into chutes lined with alternating metal and insulating plates that would cool and stretch the arc.
But I've seen enough stuff that I know I haven't seen everything :-)
daestrom
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On Wed, 14 Oct 2009 17:30:15 -0400, daestrom wrote:

Interesting - not seen those before. 'ours' were WWII-vintage, and there was compressed air in the same room as part of the air-start system for the generators, so I suppose it was no big deal to route it to the electrical switchboard too.

:-) I'm sure there were all sorts of ways and means of extinguishing arcs, though - some of which may have worked better than others!
It'd be interesting to know what larger power stations etc. did, too. Had some friends in NZ with a smaller plant (2,500 kVA) but I've not talked to them in quite a while, and I don't recall anything obviously resembling breakers on the site, although I assume they were there somewhere!
cheers
Jules
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Jules wrote:

Another variant that I worked with was spring to open and the bottom side of the mechanism pushed a plunger in a cylinder to make a 'gush' of air that was directed from below the contacts, up between them into the arc chute. Of course it was just a short burst of air, but the idea was to blow the hot gases up into the chute where the plates would separate and cool them.
daestrom
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------------- High voltage air blast breakers for AC have been around since the late 40's. They were/are modular with series sections and could then be extended to higher voltage by adding sections. The contact opening in a section was about 1 inch and 600psi air was driven through the arc, extending it towards a vent but not actually interrupting the arc until the arc naturally collapsed at current zero- then the arc products were blown out and the gap filled with good dielectric (high pressure air). A two gap section was good for 72KV and 2 of these in series for 161KV. Two gap sections could be linked together and put on longer columns at higher voltages there was a loud bang when they operated. The advantage of these breakers from Europe was that they were smaller, lighter, faster and cheaper than the oil breakers in use up to that time in North America. There was a bit of a war of words going on in IEEE PAS regarding the relative merits of bulk oil breakers and air blast breakers and air breakers won out. Even the old circuit breakers at, say 15KV up whether oil or air blast operated on the principle of removing arc products, replacing them with good dielectric, when the current went through zero. This principle is used for HV minimum oil and SF6 breakers (blast of oil or SF6 through the gap).

------------ At lower AC voltages- say 5-15KV such breakers are often used- You could take one of these and derate it to about 400-500VDC and it would likely work. That current zero every half cycle makes a big difference.

Me too
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wrote:

We need big, engine block sized solid state switches. :-)
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windcrest wrote:
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Have you had any experience with high frequency AC power systems? I've come across 400hz AC power in some old computer installations and seen a lot of military surplus aircraft power equipment that used 400hz AC power. My assumption has always been that higher the frequency, the smaller the mass of the transformers not only making equipment smaller but lighter.
TDD
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Very common (standard?) in aircraft.
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wrote:

In addition to smaller generator/motor and transformer sizes and weights for a given power, the 400Hz machines can be driven at higher speeds eliminating some or all gearing in high rpm aircraft usage (up to 24000 rpm at 400 Hz vs up to 3600 rpm at 60 Hz. ). For aircraft the distances involved are short so that inductance and capacitance are not a problem .
In general, for land based applications the advantages are outweighed by the disadvantages because of the distances involved.
Switching power supplies were not an option in those days.
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Don Kelly
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Yes, silly. 400Hz is still the standard for aviation.
Use some sense. Why would they *downgrade* to a heavier system with zero co-compatibility?
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wrote:

Filter capacitors and inductors too. It's not uncommon for switching power supplies to be above 1MHz, also to keep the size of components (and costs) small.
...and transformers get *very* big at DC.
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