electrical power

That is why broadband over power lines looks so attractive to them.

[Snip] [Snip]

and I didn't - it was someone else. I

I still don't know what the real question is. Others have made guesses.

What union? - you must have strange ways in the USA

I can't be precise on the furthest distance but where I live at the moment I'm about 100 metres from the transformer.

But really it will depend upon the size of the cables in the street to bring the IR volt drop to within allowable limits under worse case conditions. I think in the UK the voltage must be 230v +10 -6%.

*You* are the one complaining about having to be sloppy because someone else was ignorant.

Such is the Usenet.

Sheesh.

------------------ Aren't you ashamed for trying to help and guide someone rather than cast them out as idiots?

There are quite a few "sick" engineers, including those who teach engineering when the "secret handshakes" were handed out. You, Daestrom, Paul H. etc. I hope I can be included in your company.

I visited a newsgroup a year or two ago about HVAC systems. I've dabbled in that over the years and thought I'd have a look see. Now there was a group that not only had secret handshakes, they had special door knocks and special authentication via emoticons. If you weren't able to rattle off fifteen buzzwords and cite a few certifications you were promptly drummed out of the club. Okay, maybe that's an exageration, but they were a pretty tight little clique and had no interest in helping a novice or someone 'not in the trade'.

Oh well, maybe they're like good scotch and get mellower with age :-)

daestrom

Well, , I guess so.

Me? This power stuff is Greek to me. I avoided it like the plague in college (I do microprocessor and logic design). I find it interesting now, so read what you folks here have to say. I've been peeking at your hands.

I know *exactly* what you mean. The HVAC nuts are all over the homeowner groups. To hear them tell it, it's the hardest job on the planet.

No. Like old spinsters, they just get crankier.

|> Primary distribution voltages vary from 2400 volts, line to neutral |> (4160 volts line to line) up to 34 kV line to line. | | These are US figures. In the UK we have 275kV, 132kV, 32kV and 11kV before | the local distribution which is 415V (all the above being 3 phase voltages)

You have transformers to drop 275kV down to 240/415V directly?

It sounds like the OP is referring to distribution, rather than transmission. But maybe the distinction needs to be explained for his benefit.

|> In the USA, each |> phase is stepped down to 240 volts with a 120 volt center tap for |> residential loads. In other countries, the service voltages differ (220 |> V is common in Europe, for example). | | it's officially been 230V for the last 4 years.

As I understand it, the official voltage is "230 plus or minus 10" which lets everyone supplying 220 or 240 off the hook. So some places in EU will have wimpy power and some will have some boost. But I think the big idea is that any electric power utilization product for the EU market must be able to accept the full 220-240 range by design.

On Tue, 23 Oct 2007 08:30:57 +0100 charles wrote: | In article , | wrote: |> On Mon, 22 Oct 2007 05:38:07 -0700, snipped-for-privacy@charter.net wrote: | |> >Iam doing an english technical report and have a question to ask to |> >help finish the report. I was wondering what the electrical power |> >would be on the electrical lines in a residential area feeding the |> >houses before it goes to the transformers for the houses, and what the |> >power would be to a industrial building. I know that the power to an |> >industrial would vary from plant to plant depending on what they do, |> >but if I can get an idea it would help. Thanks | |> The 2 most common on residential streets is 4kv and 13kv. If there is |> only one insulator it is probably 4kv and if it is a stack it is |> probably 13kv (based on what FPL does around here. | | That might apply in the USA; in the UK only 415V is used in residential | streets. The next voltage up is 11kV.

For supplying the transformers that step down to the 415/230 (or just 230 if single phase) levels for homes and most businesses, what is the range of possible voltages than are allowed to do that directly? For the USA, I have seen listed in catalogs, transformers that go as high as 34.5kV in with outputs to 208/120 and 480/277, though mostly the latter.

No, normally 11kV feeds the 240v transformers.

That list is missing 400kV, and the 32kV should read 33kV.

No. Distribution to final substations is 11kV. Substation to house (i.e. the street level distribution) is 240/415V.

In some sparsely populated areas, I believe 33kV to 240/415V is done.

Nearly always 11kV, but I believe 33kV can be used too in sparsely populated areas.

11kV is also a standard supply voltage for businesses, if they want higher than 415/230 (and probably more than 1MVA load).

| Iam doing an english technical report and have a question to ask to | help finish the report. I was wondering what the electrical power | would be on the electrical lines in a residential area feeding the | houses before it goes to the transformers for the houses, and what the | power would be to a industrial building. I know that the power to an | industrial would vary from plant to plant depending on what they do, | but if I can get an idea it would help. Thanks

This is probably a little more than you are asking for, but maybe there will be some piece of info you can add to the paper to explain why some of the voltages are used.

Since your email address is @charter.net I'll presume you are in the USA.

The electrical power industry divides power lines into three voltage categories labeled LV for low voltage, MV for medium voltage, and HV for high voltage. In general, MV is used for what is called distribution, and HV is used for what is called transmission. Transmission usually goes directly from one substation (often at a power generating plant) to another. Distribution goes from a substation to multiple transformers that serve typical customers.

The common house/office voltage is officially 120 volts, although many people still refer to it as 110 volts and say "one ten". 110 volts was the standard Thomas Edison used for his first power service in New York City. He also used the idea (although I don't know if he invented it) of splitting the voltage between two polarities (his system was DC so it would be plus and minus), so it was actually 220 volts between the two far wires, and only 110 volts between either of those wires and the wire in the middle. This allowed him to connect light bulbs to 110 volts and get some of the advantages of higher voltage distribution (to run wires at greater distances without so much loss of voltage due to resistance in the wires).

Most homes in the US are supplied with true single phase power, using the split phase system that Edison uses, but with AC. So the voltages are 120 volts between either of the 2 "hot" wires, and the center wire which is grounded and called "neutral". The voltage between the 2 hot wires is 240 volts. With some variation in voltages, this system is also used in some other parts of the world, notably North and Central America, parts of northern South America, most of the Caribbean, as well as Japan (only 100 volts) and Taiwan. Some places get as much as 127 volts.

In other parts of the world, homes and offices typically get voltages that range from 220 to 240 volts between the hot wire and ground. Many also get three phase power at voltages from 380 to 416 volts measured between any two (out of two or three connected) hot wires.

The AC frequency in the USA is 60 Hz (cycles per second). Most of the rest of the world uses 50 Hz. Some places have the lower voltage with

50 Hz and a few places have the higher voltage with 60 Hz. Japan and Brazil have both power frequencies within the same country.

In some cases, notably large buildings, three phase power is cheaper to provide than single phase power, and even though homes still typically only get 2 hot wires fed, (three phase has 3 hot wires with the cycle timing shifted so each wire is 1/3 of a cycle different from the others) the voltage between the 2 hot wires is only 208 volts instead of 240.

Industrial buildings making heavy use of electrical power will get that power typically at a voltage of 277 volts, with 480 volts between any pair of hot wires. It's almost always three phase because large motors need it. If single phase loads are the main usage, it still needs to be well balanced usage over the three phases used in the distribution. In a few places these voltages will be 347 volts and 600 volts, mostly in Canada. Heavy industry will often use much higher voltage and have power bills in the millions of dollars. Many coal mines use a voltage that is a combination 577 volts and 1000 volts. Many industrial facilities and electrical railways have special power frequencies. A few even have DC power. In other places in the world, industrial power can be available in many other voltages, such as the combination 690/400 volts in Europe.

The distribution of power in a typical residential neighborhood in the USA will have a mix of LV to feed 2 to 6 homes from one larger transformer and MV to feed those transformers. The LV will be the 120/240 single phase power described above. The MV will typically be between 6900 volts and nearly 8000 volts, with 7200 or 7970 volts being common in many areas. That is the voltage between a hot wire and the grounded wire. The voltage between two hot wires in a three phase system (the distribution is almost always three phase, or just one hot wire) is about 1.732 times as much, a figure derived from the mathmatics of sine waves (trigonemtry) and is the square root of three.

In possibly rare cases, the distribution can be an even higher voltage, as much as 34,500 volts. This would typically be used only if there are special reasons such as a greater distance from the last substation, or heavy power users in the area.

When you observe overhead power lines, notice how many separate wires are on insulator stand-offs, and how big those insulators are. Big insulators suggest a higher voltage (but do not assume always so). One or two wires suggests single phase while three or four wires suggests three phase. In some cases you will see even more wires, such as six or more. These may simply be separated circuits for special cases, such as backup power to a hospital, or a separate circuit that will split apart further away from the substation.

Transmission lines supply power from one area to another. You can usually see several transmission lines from a power generating plant substation going off in a few directions to supply power to many locations or connect to the power grid (many transmission lines interconnected with substations). The voltage on these can range from 69,000 volts to 765,000 volts or more in a few rare cases (above this level is much more of a technical challenge).

The power industry refers to the voltage levels of 120 to 600 volts as LV (low voltage). But inside a home, the designations change and we use "high voltage" to refer to the 120/240 volts you could easily be electrocuted with and "low voltage" for a reduced voltage that is 30 volts or less, typically only 12 volts, commonly used for special lighting systems. Incandescent lights work better when the voltage is lower because it uses a shorter and thicker filament that runs at a higher temperature (this actually produces more light and less heat for a given amount of power, and that light is a whiter quality of light better suited for task lighting). The lower voltage also allows for the use of uninsulated track lighting systems since contact with this voltage is much less likely to hurt anyone, and requires touching two wires since the systems are required to be isolated from ground.

The only 'secret handshake' I can recall is the one with the middle finger extended.

It might be a good idea (for the OP) to state in which country you refer to.

240/415 is a three phase wye configuration typically found in Europe. In North America, we distribute single phase 120/240V to residential customers.

I thought that was the new retirement plan.

On Sun, 28 Oct 2007 19:16:10 +0000 (GMT) charles wrote: | In article , | wrote: |> On Mon, 22 Oct 2007 20:49:27 +0100 charles wrote: | |> |> Primary distribution voltages vary from 2400 volts, line to neutral |> |> (4160 volts line to line) up to 34 kV line to line. |> | |> | These are US figures. In the UK we have 275kV, 132kV, 32kV and 11kV |> | before the local distribution which is 415V (all the above being 3 |> | phase voltages) | |> You have transformers to drop 275kV down to 240/415V directly? | | No, normally 11kV feeds the 240v transformers.

What is the highest that can be used to feed 240V transformers directly?

Other than working in hot or dirty places, it's one of the simplest jobs in a home. I wrote software for a HVAC company, years ago, to calculate the heat load, select the proper equipment, and print out the bid. They were yammering about how hard the work was, and how NO home owner was smart enough to do their own work. What a pathetic bunch of maroons. :(

I was working at a TV station in Orlando in 1987. They had a 5 ton AC unit to cool the equipment racks. It barely kicked on, yet the equipment was running hot. They had been to the station a half dozen times, once with a factory "Engineer" and they couldn't figure out what was wrong. I took one look and spotted the problem. All the vents were in the ceiling of the tiny area. The face of the racks were in the control room, and there was a row of sliding doors in the hallway behind the racks to access the wiring. The air above the racks was 60 degrees F. The air inside the racks was over 100 degrees F. All the cabling and the layout of the racks and equipment was causing severe stratification. I asked them to remove one of the supply vents and attach a piece of flexible ducting, and drop the other end to the floor. They all jumped on me, bragging about how many years experience they had, combined, and that I couldn't POSSIBLY know what i was talking about. I shrugged and said, "Then prove me wrong, if you can." They got pissed, but one of them went to his truck for his tools and some duct. He hooked it up and dropped it to the floor. i set their thermometer on the top of a piece of equipment, and closed the doors.

15 minutes later, the equipment cabinets were cold to the touch, and they were all red faced. They had screwed around for two years with it, while the station spent thousands of dollars per quarter on failed components and kept the engineers busy, trying to keep the studios up and running.