Bill,
My experience with electrical distribution systems is biased by my years in
the wind tunnel business at Arnold Engineering Development Center. There,
because of the large horsepower motors in use, the industrial distribution
was 161kv, run underground, with substations at each facility. The
"housekeeping" power, to buildings, etc, was overhead 13.8kv. I seem to
recall that the overhead main lines here in town are about half that, around
7900 volts, but I have no real frame of reference for that number. Whatever
it is, it is reduced to 120 volts at the "pole" transformers.
I suspect that your historic street lights were incandescent lamps. Our
street lights are both mercury vapor and sodium vapor, and appear to be
connected directly to the distribution lines, though they may well include
their own transformers inside the housings. They are each controlled by
individual light-sensing switches on top.
Jim Nichols
Tullahoma, TN USA
----- Original Message -----
From: "Sue Pearce" <bs.pearce@xxxxxxx>
To: "Olympus Camera Discussion" <olympus@xxxxxxxxxxxxxxxxx>
Sent: Thursday, February 25, 2010 9:24 PM
Subject: Re: [OM] Purchase of new camera case successful
> Jim,
>
> Yes., the "line" voltage is probably around 480 Volts. I know this because
> our homeowners association has the responsibility for our historic street
> lights, place in about 1920. For our English and European friends, this is
> considered history in the USA.
>
> Our lights were originally on a lower voltage, and when we restored
> things,
> the electric company hooked them up and said This is OK, send them the
> juice. All the underground lines from light to light melted.
>
> Ah, well, the Electric Company paid for the new lines...
> Bill Pearce
> ----- Original Message -----
> From: "Jim Nichols" <jhnichols@xxxxxxxxxxxxx>
> To: "Olympus Camera Discussion" <olympus@xxxxxxxxxxxxxxxxx>
> Sent: Thursday, February 25, 2010 5:42 PM
> Subject: Re: [OM] Purchase of new camera case successful
>
>
>> Jon,
>>
>> Though I'm not a EE, I can give you some general concepts of power
>> distribution in the US.
>>
>> I live on a corner lot, alongside a fairly busy throughfare. There is a
>> 3-phase distribution line along that street. Feeding our homes are a
>> connection to a single phase of that line, and the common neutral. These
>> go
>> to a distribution transformer which supplies three or four homes. I have
>> little knowledge of what takes place in the transformer, but the output
>> to
>> each home is made up of two 120 volt legs and a neutral. These feed the
>> breaker box busses. 120 volt branches are connected between either of
>> the
>> two hot legs and the neutral. 240 volt circuits connect between the two
>> hot
>> legs. Perhaps someone else can elaborate what happens in the local
>> transformer. I suspect that the transformer drops the voltage down to
>> 120
>> volts and feeds two separate secondary windings, which are then fed to
>> the
>> house breaker panel, along with the neutral.
>>
>> Very few homes are served with 3-phase power feeds.
>>
>> Hope this helps.
>>
>> Jim Nichols
>> Tullahoma, TN USA
>> ----- Original Message -----
>> From: "Jon Mitchell" <olympus@xxxxxxxxxxxxxx>
>> To: "'Olympus Camera Discussion'" <olympus@xxxxxxxxxxxxxxxxx>
>> Sent: Thursday, February 25, 2010 5:25 PM
>> Subject: Re: [OM] Purchase of new camera case successful
>>
>>
>>> Hi,
>>>
>>> Apologies for answering my own questions. Not such an "American" trait
>>> in
>>> broadcasting any more though - it's spreading fast. Not that that's an
>>> excuse ....
>>>
>>> Not sure about moving supplier though. They all get the power from the
>>> same
>>> place. I think of it as a wholesale arm of the National Grid selling
>>> the
>>> power to any of the retailers (they are bound, I believe, to give them
>>> all
>>> the same deal). The retailers then sell it on to you. That's progress
>>> for
>>> you !
>>>
>>> Now on to a more interesting question for other members of the list
>>> (which
>>> I
>>> won't answer myself .... 'cos I can't !). There's a lot of talk about
>>> different power "legs" and "phases" to the same house from our US
>>> friends
>>> here. I have little idea how the power supply works in the USA (other
>>> than
>>> it is 110v 60Hz AC), but is the implication that you have more than 1
>>> phase
>>> in your homes ? Over here you can get either a single-phase supply or a
>>> 3-phase supply. Very few (if any ?) homes have a 3-phase supply, as
>>> these
>>> are intended for industry.
>>>
>>> Are your houses wired with some sockets on one phase and some sockets on
>>> another ? Doesn't this pose problems ? What if you connected 2 devices
>>> to
>>> 2 separate sockets that were on 2 separate phases - and then connected
>>> the
>>> devices together (VCR to TV via a SCART, for example). At best, nasty
>>> interference. At worst CABOOM, no ?
>>>
>>> And what about balancing the phases ? When I've played with 3-phase
>>> supplies (lighting rigs, for example) a lot of care is taken to ensure
>>> that
>>> the phases are fairly evenly balanced (approx same load on each phase).
>>> How
>>> do you do that within the home, when most home-owners don't understand
>>> this
>>> stuff ?
>>>
>>> I'm not questioning whether it is right or wrong, better or worse, but
>>> am
>>> interested in how it is done elsewhere.
>>>
>>> Oh, and most scary thing seen whilst working with 3-phase ? A colleague
>>> ran
>>> a long run of pre-terminated 3-phase power cable (120Amp, or
>>> thereabouts)
>>> over the roof of a stadium. He realised afterwards that he had run it
>>> the
>>> wrong way around (male & female connectors at wrong ends for the
>>> required
>>> usage). Whilst I agree it would have been a lot of work to de-rig and
>>> re-rig the cable, I am sure that it would have been easier (and safer)
>>> to
>>> chop the ends off and remake them the right way round rather than make
>>> 2x
>>> 3-phase Gender-Bender cables ! That was one VERY scary cable.
>>>
>>> Second most scary 3-phase incident ? The 3-Phase A0 photocopier we had
>>> at
>>> work until a couple of years ago. I still can't comprehend why you'd
>>> need
>>> 3-phase power for a photocopier !
>>>
>>> Anyway, this is all wildly off-topic (though fun).
>>>
>>> Jon
>>>
>>>
>>> -----Original Message-----
>>> From: Chris Barker [mailto:ftog@xxxxxxxxxxxxxx]
>>> Sent: 25 February 2010 21:48
>>> To: Olympus Camera Discussion
>>> Subject: Re: [OM] Purchase of new camera case successful
>>>
>>> Thanks for that Jon. But there is something you can do about it: move
>>> supplier, complain to your current supplier, to Ofgen etc ...
>>>
>>> And, don't you start sounding like an American broadcaster, asking your
>>> own
>>> questions ....
>>>
>>> ... or Conservative MP :-)
>>>
>>> Chris
>>> On 25 Feb 2010, at 20:26, Jon Mitchell wrote:
>>>
>>>> FWIW, we looked into this at work recently - problems at some of our
>>>> sites
>>>> with very low voltage. UK spec was changed recently to harmonise
>>>> across
>>>> Europe. I don't have the exact figures to hand, but it used to be
>>> something
>>>> like 220v in Europe and 240v in UK. Now it is 230v in UK and the rest
>>>> of
>>>> Europe. How did they get away without changing all of the National
>>>> Grid,
>>>> substations, etc. ? They fudged the error-factor so now UK is
>>>> something
>>>> like 230v +15%/-6% and rest of Europe is something like 230v +6%/-15%.
>>>> Phase is much more accurately defined, and has a far smaller margin
>>>> before
>>>> it becomes "out of spec" - but that was always the same across UK &
>>>> Europe
>>>> anyway. In reality, nothing has changed in the power supplied either
>>>> in
>>> UK
>>>> or rest of Europe, but now manufacturers have to cope with a wider
>>>> voltage
>>>> range if they want to sell products across Europe.
>>>>
>>>> Anyway, back to the point, yes - in theory the power companies are
>>> required
>>>> to maintain a consistent voltage (within an alarmingly wide margin of
>>>> error). In practise, however, they regularly do not maintain this.
>>>> Especially in more rural areas. But who can do anything about it ? As
>>>> someone else said here - the general attitude of the power companies is
>>> "you
>>>> get what you're given".
>>>>
>>>> Does it suck ? Yes. Does it bother me ? A little. I know a couple
>>>> of
>>>> SERIOUS hi-fi nuts who have taken matters into their own hands and
>>> installed
>>>> some serious power-conditioning units (basically, AC-DC-AC conversion)
>>>> and
>>>> run a separate ring-main just for their hi-fi components. Can I hear a
>>>> difference ? Well, yes - but more to the point is that the cost of the
>>>> hi-fi kit in question means it is worth a sizeable investment in power
>>>> conditioning to stop it going boom when the power drops (or rises) out
>>>> of
>>>> spec.
>>>>
>>>> Gosh. 2 topics in a week that I can reply to with some experience !
>>>> What
>>>> is this list coming to ... ;-)
>>>
>>> --
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>>>
>>
>>
>> --
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>
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