High voltage transmission lines

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High voltage transmission lines

Postby moonshadow » Fri Sep 27, 2019 4:00 pm

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Re: High voltage transmission lines

Postby denimini » Sat Sep 28, 2019 1:19 pm

Oops, damn. I missed the "don't try this at home" message. My breadboard will never be the same :)

Always can learn somthing new; I didn't know about the Stockbridge damper.
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Re: High voltage transmission lines

Postby crfriend » Sat Sep 28, 2019 2:45 pm

denimini wrote:Oops, damn. I missed the "don't try this at home" message. My breadboard will never be the same :)

Having caused inadvertent incandescence in power-carrying conductors a few times myself I've learnt my lesson on that one. Watching what happens to wire-wrapped 26-gauge that's been accidentally strapped from VCC to ground is, shall we say, "jarring".
Always can learn somthing new; I didn't know about the Stockbridge damper.

I see those all over the place and always wondered what they are. Now I know! Thanks for that one!

One thing the video didn't go into is how all the generating stations are synchronised with each other in both voltage and phase. I need to read up on how one mechanically positions, say, a generator attached to a multi-thousand horsepower water-turbine to align perfectly with what the "grid" is doing.
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Re: High voltage transmission lines

Postby beachlion » Sat Sep 28, 2019 4:28 pm

crfriend wrote:
denimini wrote:...... One thing the video didn't go into is how all the generating stations are synchronised with each other in both voltage and phase. I need to read up on how one mechanically positions, say, a generator attached to a multi-thousand horsepower water-turbine to align perfectly with what the "grid" is doing.


Maybe this will enlighten you.
http://ewh.ieee.org/soc/pes/newyork/Arc ... %20169.pdf

In the Netherlands, with the Erasmus bridge in Rotterdam, there were similar problems with vibrations. After some research they found out that rain was amplifying the problem. The wind caused turbulence around the cables. The thin layer of water was moved from one side to the other by the turbulence. This changed the overall profile of the cable and made the problem worse. Connecting the cables with thinner cables was the solution to minimize vibrations.
https://www.researchgate.net/publicatio ... _Rotterdam
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Re: High voltage transmission lines

Postby JohnH » Sat Sep 28, 2019 4:39 pm

While I was earning my B.S. Electrical Engineering degree I participated in a lab exercise of bringing a generator online.

I recall the following:
1. You determined the phase sequence between the 3 phases by using a small multipole motor and observing the direction of rotation.
2. You connected light bulbs between each of the phases from on line to the rotating generator that was not loaded. The bulbs were connected in the same rotation for the generator and online power.
3. You then adjusted the angle between the online power and the generator until the light bulbs no longer glowed.
4. Then you could connect the generator to online power and apply torque to the generator to feed back power to the online grid.

The motor driving the generator was a synchronous motor so we did not have to worry about frequency. You would adjust the speed of the generator so its electrical frequency would be the same as the grid before performing Step 3.
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Re: High voltage transmission lines

Postby trainspotter48 » Sat Sep 28, 2019 5:43 pm

As previously mentioned, it is necessary to match the speed (frequency) and voltage of the incoming machine to the existing 'grid'. There is normally some kind of speed control arrangement on the 'prime mover' be it a steam turbine, diesel engine, gas turbine etc. The verification of direction is normally only required on initial commissioning, or after any major work capable of disturbing the connections, and for machines in the 100s of Kw to 100s of Mw rating area, it is usual to use a synchroscope in conjunction with voltage transformers.
The incoming machine is accelerated up to approximately system speed, and brought up to voltage. Now the synchroscope (a sort of one handed clock) is brought into service to see if the incoming machine is running 'fast' or 'slow' compared with the system. The speed is adjusted such that the incoming machine is running slightly 'fast', and the synchroscope will start to sweep slowly clockwise around the dial. The paralleling switch/circuit breaker is then closed as the 'scope' passes through approx. 11 o'clock. The machine is now 'on load', and the speed control (throttle) is increased to allow it to take up generation. Further adjustments of field and/or transformer tapping then take place to suit the system reactive loads.
Obviously, to take a machine 'off load', the output is normally reduced to near zero before the switch is opened, although the switchgear has to be capable of isolating the machine in a fault scenario.
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Re: High voltage transmission lines

Postby K_Highlander » Sat Sep 28, 2019 6:41 pm

crfriend wrote:Having caused inadvertent incandescence in power-carrying conductors a few times myself I've learnt my lesson on that one. Watching what happens to wire-wrapped 26-gauge that's been accidentally strapped from VCC to ground is, shall we say, "jarring".


I recall using that technique to find an inadvertent VCC to ground short on a large (20" by 20") wire-wrap panel with hundreds of sockets. Unfortunately it also "fried" adjacent wires. It was quicker to fry, than to search thru hundreds (or thousands) of wires for the short!
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Re: High voltage transmission lines

Postby dillon » Sat Sep 28, 2019 7:22 pm

When I was searching for land investments I was intent on finding a large tract with a 3 phase line, if not major transmission lines, for a solar farm. But I ended up buying for beauty and not practicality. As the country moves toward a low-carbon energy economy, we can pick up about 15% efficiency simply by reworking our power grid. When we do, it must be with the intent of restoring the historic concept of electric utilities as corporate-consumer partnerships, rather than the private corporate entities that the utilities would prefer to pretend they are. They were established as, and still operate as, government-granted monopolies and are guaranteed a minimum return on costs by most states.

An upgraded grid needs the capability and mandate to accommodate customer generated power, i.e. home-farm-small business electricity from various non-carbon sources, such as PV, wind, bio-methane, and captured waste heat from industry. That way we are all invested and engaged in the nations energy future. With the rapid improvements in PV efficiency, including “ shine-through” technology, clear window panes that convert a portion of the light passing through to electricity. The future for renewable energy is bright, and it should be.

God put the sun to fall on our faces, the wind to blow our hair, the sea waves and currents to awe us, the tides to set our clocks by. And he gave us the intellect to harvest and harness these gifts. We chose to ignore the gifts because they did not suit our worse nature of greed. We have the chance and challenge to redeem ourselves, and the capability to do so.
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Re: High voltage transmission lines

Postby crfriend » Sun Sep 29, 2019 3:06 am

dillon wrote:When we [rework the "grid"], it must be with the intent of restoring the historic concept of electric utilities as corporate-consumer partnerships, rather than the private corporate entities that the utilities would prefer to pretend they are. They were established as, and still operate as, government-granted monopolies and are guaranteed a minimum return on costs by most states.

One of the things I like about New England is the number of municipal power companies that operate on a non-profit basis such that power may be provided to the populace of the various municipalities at reasonable cost and high reliability. I grew up in a town with a municipal supplier, and have spent the last 30 years of my life the same, and I could not be happier.

I lived for a few years in a town that was "supplied" by a for-profit "utility" that, in a word, sucked. Once a week, guaranteed, I'd have a second or two cut that'd crash any known computer and screw up all the digital clocks. I coined the term "edison" as a verb to describe the phenomenon, first as a play on the "utility" that was allegedly supplying the town with power and secondly as a play on Edison's coining of the term "to westinghouse" to mean electrocution (viz "the war of currents"). Hence, the remark of, "We got edisonned yesterday and it took us until now to get everything back on-line again!" Hilariously, this has seeped into the common lexicon as I've heard folks living in places that have for-profit "utilities" use the term in public. Those shenanigans practically never happen with various "Municipal Lighting Plants", which many of them call themselves. Unless there is high-profile work going on my computers run for hundreds of days between glitches -- something unthinkable in an are "served" by a for-profit entity.

An upgraded grid is absolutely necessary, and I do not think that the for-profit sector is capable of doing it. If "micro-generation" actually works, it might be possible to relegate "The Grid" back to its original status as the backup of last resort instead of the primary provider. But that's going to take a lot of time, money, or -- likely -- both to achieve. Who's going to bankroll that?
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Re: High voltage transmission lines

Postby dillon » Sun Sep 29, 2019 3:28 am

The plus side of a “green” electric future is that the investment can be recouped by multiple means. First are slightly higher electric rates to pay for dedicated federal bonds, possibly yielding half a point higher than T-Bills and, second, by carbon emissions taxes. Step one for a practical Green New Deal.
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Re: High voltage transmission lines

Postby denimini » Sun Sep 29, 2019 11:28 am

Our town is on the state grid now which is a shame because the cost of transmission lines would have easily paid for photovoltaic to supply the town. Big losses over those distances and the there is a power outage at least every 2 weeks. If there has been rain, which often happens with a storm, the power can be off for days as crews can not get out even if the fault is spotted from the air. The local service (gas) station has a generator to run their bowsers.
We used to have a selection of diesel generating plants, mainly Rustons which were privately owned. A rough bush turnout but was more reliable than present day grid power.
The owners wanted to retire and sold to the State Corporation.
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Re: High voltage transmission lines

Postby JohnH » Sun Sep 29, 2019 9:01 pm

It would not surprise me if eventually renewable energy replaces the hundreds of kilometers of power lines in the remote areas of Australia due to maintenance costs of the lines. A group of farmers, ranchers, and other consumers could maintain a cooperative operation for renewable energy with diesel backup.

That could happen in rural areas of the US but costs of renewable energy might need to come down, since the US is much more densely populated with the average distance from producer to consumer being much shorter. However if modern renewable energy technology had been available in the 1930's, when there was the push to make electricity available to rural areas, the means of doing might have have been completely different.

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Re: High voltage transmission lines

Postby crfriend » Sun Sep 29, 2019 10:35 pm

JohnH wrote:It would not surprise me if eventually renewable energy replaces the hundreds of kilometers of power lines in the remote areas of Australia due to maintenance costs of the lines. A group of farmers, ranchers, and other consumers could maintain a cooperative operation for renewable energy with diesel backup.

This, oddly, is where the "third world" has a leg up on the USA. They're "undeveloped" (from a technological viewpoint) compared to the industrialised countries and thus have a wider range of options open to them compared to the dictated ones in the "developed" world. Notable amongst this plethora of options is what they're doing with wireless telecomms -- which outstrips much of the "developed" world and especially the USA with its historically copper-wired infrastructure which still isn't entirely depreciated. Power is the same way. The for-profit power companies will -- and are -- fighting the micro-generation notion tooth-and-nail to preserve their profits.

Sitting atop the house I currently dwell in is a 10 kW-rated PV array and I'm having a ball watching the thing light up on the house network. During "bright times" the array is putting out quite a bit in excess of the draw from the house, and this is charging the batteries that may be able to carry the house (and my computers) for the night. Everything's still in flux, but we may actually wind up being a producer instead of a consumer for much of the week. Time alone will tell.

There's no real hope for cities, larger towns, and places that don't have municipal-run power companies. The profit-motive is too strong to allow any change in the status quo. But, where I currently dwell is a nice little experiment in renewable electricity -- and it renews each day the the sun rises. I'm already noticing the diminution of daylight hours and the effects of lowered solar zenith -- and that's just with eyeballs and raw numbers without graphing and the like.

I'm developing ideas on how I can use the data that the system provides -- and the possibilities are almost mind-boggling. Sure, sampling the power produced by the array, how much is going into the batteries, and how much is bing pushed back to "the street" is easy. If I can find a way to acquire the power output of each of the panels on the roof is I can use the thing as a sky-facing camera of sorts to determine wind-direction and velocity at the cloud-layer. It all depends on how quickly the system samples its performance.
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Re: High voltage transmission lines

Postby JohnH » Sun Sep 29, 2019 10:45 pm

I read that NIPSCO (Northern Indiana Public Service Company) which serves the northern third of Indiana is going to phase out coal burning plants in favor of renewable energy as the projected costs with renewable energy is going to be less than coal. I also read there might be a time for fossil fuel for transportation might have to come down to $9.00/barrel of crude to be competitive with electric vehicles.
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Re: High voltage transmission lines

Postby 6ft3Aussie » Mon Sep 30, 2019 7:08 am

I have some friends who live in the bush between Bathurst and Orange, NSW (Australia) and they are completely off the grid for electricity, water and sewerage systems.
They looked at the cost of an off grid system in comparison to installing about 500m of line in from the road and having to pay for an 11kV to 415/240V pole transformer as well and then being in a rural area having the unreliability factor of being in the bush, to installing and setting up their own solar system with battery storage. Off the grid solar was substantially cheaper and the added ongoing cost benefit is a winner.
They are like me, fairly tech savvy and were able to source the gear cheaply enough and do the installation themselves.
My ultimate goal would be to do something similar, solar panels are cheap as chips with the domestic grid-connect solar industry and batteries are cheaply available (near new) if you have the right contacts.

Their system was initially a 12V DC system, but over the years it has become as 24V DC system with inverter to run their 240V AC household equipment, they have a large deep cycle battery bank and I forget how many solar panels on their roof, but they don't run out of electricity and have never had a power bill in about 20 years.
They have two 50000 litre and one 20000 litre water tanks for supply plus a 500 litre header tank about 7 metres above ground to give them sufficient pressure in the household taps, with hot water provided by a combination of solar hot water and a wet back heater in the wood fired stove/oven, which is useful in the winter when it can get down to -5°C.

In the video link give, I like the use of two microwave oven transformers to form a short line at around 2kV.... Just keep those fingers well away from that one... it would do more than bite.
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