Is this Govenment a load of fools - part p

[ban-all-sheds]

Err - sorry to be a bit thick and that, but I have just come home in my motor car. Seems to run by something called electricity at 12v - whatever that is I do not know I am sure.

Let me see now - just gone out to look at the cable sizes - can't see any as thick as your arm. Total fuses 30. Total rated amps 505.

OK - "thick as your arm" was a bit of an exaggeration. But not much - FWL's sizes above of 400mm2 and 780mm2 equate to diameters of (only ) 22.5mm and 31.5mm, so with insulation say 25-35mm? So a flat-twin cable would have a major axis of 52-72mm? How wide is your wrist? Mine's about 70mm...

Ah, I get it - it has a wiring loom and of course the car itself is neg earth- whatever that is.

Of course we could not possibly use that system in a house - goodness no.

Now, we couldn't. People would not want wiring looms in their houses, and also don't forget that as our houses are not made of metal which provides a handy common return path for everything, we'd need twice as many cables as the car.
Also theres the little matter of voltage drop to consider, since most people's houses are a fair bit bigger than even a large car.
I don't know if you've ever tried to introduce a new electrical item, or circuit into a car - it isn't easy, and not just because it's cramped. I don't think many people would thank you for introducing the same level of difficulty to their homes.
Your car has 30 fuses. Count the numbers of lights and other electrical items on board and then do the same for your house.
Your fuse values add up to 505A at 12V. This is equivalent to less than a single domestic ring main.

We all need self satisfied plonkers who can only think in one direction - backward and are more interested in trying to prove something wrong than a bit of lateral thinking.

There's nothing wrong with lateral thinking, but any idea that you come up with, by whatever means, has to work if you want to put it into practice. And hundreds of circuits in a house supplying individual lights etc is not a workable idea. A shower cable as thick as my wrist is not a workable idea. If pointing these things out makes me a plonker in your eyes so be it.

 

[ban-all-sheds]

Dear me Ban All Sheds.

I am sure that everyone on this forum appreciates your technical knowledge and the time and effort you spend in helping others.

It does seem to come at a price however. Blustering away at someone who has suggested something that may or may not be feasible is not a proper way to behave. Take a stress pill and go and lie down in a darkened room. You will feel much better.

One of the ways to achieve goals to set a target and work towards it.

Bluster away. Its only an idea

Is it worth pointing out that in my main detailed reply to your points I either agreed with them, or gave a non-critical, and hopefully-helpful reply to about 75% of them?

I thought not.

 

[ban-all-sheds]

Ban your a Goit!!

Your post got me interested, I followed the links (Canada one appears broken) and read EVERYTHING I could about these projects.

This did not answer my questions so I have been on the phone to National Grid and Siemans in Erlangen. No surprise that National Grid were of no help, for "security reasons" they will not divulge why they use DC over AC for this link...I think the engineer I spoke too simply doesn't know!!

I spoke to an Engineer in Erlangen who was more forthcoming, and will be sending me all the technical data I need to understand this as soon as he can either find it in English, or have his German copy translated.

The gist of this is to do with cable and electrical technology improvements.

He said that it is true to say that when National Distribution Systems were first proposed, DC suffered unacceptable volt drop and transmission loss problems due to the technology of the day. We now have the technology to make conductive materials for cables that suffer very little transmission loss using either AC or DC, but these are more efficient with DC supplies than AC. Further he explained that the technology of conversion from AC to DC and back again has dramatically moved forward in the last decade to the point where losses are now acceptable and match that of AC in some cases or are better in others.

One thing he also mentioned was magnetic field losses, with AC this cannot be helped very much, it is a simple fact of physics, with DC the situation is different. DC generates a smaller mag field for a given voltage/power, and it also saps less energy from the conductors in the process, one reason for the higher efficiency of the transmission line, however one aspect of it makes it very desirable, the magnetic field is not rotating but static, and they believe this will have less effect on the human body and less effect on nearby electronic equipment which is not grounded properly.

This is simple explanation of the reasons from a 45 minute conversation, as soon as I have the information I will create a simple to understand explanation that all can follow.

It would appear that DC is making a comeback!!

Thought you might also be interested in this: http://www.mitcheson.org/paul/grid/

 

[Big_Spark]

8. Conclusion
Investigation of the present system has shown that it represents a major capital investment. The transmission cabling alone costs around £500,000 per km to install. Making significant changes would also mean throwing away a large body of practical knowledge and experience.
In order for harmonic distortion not to become a major problem in a mains distribution system power must be transmitted as a sinusoid. Increasing the frequency of transmission could allow transformer cores, and smoothing capacitors on AC to DC converters to be reduced in size. However, there is a trade off because high frequencies increase eddy current losses. In addition, the voltage level within a domestic environment must be over around 100V so that diode rectifiers can achieve high efficiency, but must not be too high due to safety implications.

Protection of both AC and DC distribution systems is theoretically possible, but above a certain DC voltage it becomes impractical because of the physical size, complexity and cost of the necessary equipment.

Practical considerations limit signalling over the mains network to low volume control signals.

For these reasons, we recommend that no alterations should be made to the parameters of the national grid. Although there are various initially attractive methods for improving performance and efficiency, these do not prove to be practical upon further investigation. Our findings are consistent with the findings of a similar project conducted by Her Majesty's Royal Navy

Infortunately he would appear to be a minority of one were this is concerned. His argument regarding rectifiers is flawed by existing technology that is available to you and I off the shelf, but the biggest indictment is his BIAS....If you dig further..takes a while mind, but the research was co-funded by ABB and GEC Marconi..two companies heavily involved with the current Grid infra-structure.

Further, a similar report, funded by Siemans, came to almost the OPPOSITE conclusions. I find it odd that Siemans would invest nearly $600 Million over the last decade developing DC transmission systems if it truly suffered the downside in the quoted report. The fact that an American, Canadian and an Australian company have come to much the same conclusions as Siemans tends to lend weight to their arguments.

Personally I care not whom is or is not right, I just want to get my hands on the research to take a good look at it myself.

 

[phykell]

I think even if we were to have a low voltage DC supply running throughout the house (given thick enough walls to carry the cable), there'd be a significant problem with the quality of the regulation. As it stands, a typical transformer or PSU for any number of gadgets we have, may be designed to supply an individual device. For example, while the PSU to your Scalextrix might be a simple transformer with a couple of diodes, the PSU inside a PC is rather more complicated, being a switch mode device and actually supplying several different voltages, e.g. 5v, 12v, and even negative voltages. Similarly, hi-fi components may require very high quality DC at relatively high voltage - typically 35v to 50v, and it's unlikely you'll find switch mode PSUs used for amplifiers. With this in mind then, I suggest that instead of 240v PSUs, we'd end up with DC to DC convertors/line conditioners instead, probably of a similar size to the PSUs you'd hope to replace.

 

[plugwash]

i heared the cross channel interconnector is dc

is this true and do you have any idea what its specs are?

 

[Damocles]

According to the link supplied by BAS, it is 2000Mw, 270KV.

It sounded as though the reasons for choosing DC were largely due to its special circumstances.

First, using fewer separate cables was desirable, being as they are difficult to install or maintain under the sea. insulated cables are less subject to breakdown if carrying DC. Pylon lines are uninsulated so in that case it does not matter.

Second, that it was necessary to convert from ac to dc and back to ac to isolate the continental electricty system from the Uk one. they are not run in phase, unlike all the ac system within the uk. So this had to be done anyway.

I thought some electricity was transmitted through the channel tunnel. Is this the installation the article is talking about, or another?


No one has mentioned the point that for a given voltage, AC is considered safer than DC. This is because the voltage switches off and reverses 100 times per second, giving you a chance to let go.... if you are unfortunate enough to be holding something live.

 

[ban-all-sheds]

No one has mentioned the point that for a given voltage, AC is considered safer than DC. This is because the voltage switches off and reverses 100 times per second, giving you a chance to let go.... if you are unfortunate enough to be holding something live.

It's not much help at 270kV...

 

[Damocles]

Possibly not. But most people only have 240V distribution in their houses. 240V DC was considered more dangerous where I used to work. Never tried it myself, but there were stories...

 

[plugwash]

btw i saw a distribution map in one of the buildings at my university (not of the whole sountry just a band centred on manchester) and im sure there were some dc links marked on it

i gather DC is much harder to switch than AC though because AC tends to break arcs on the zero crossing points

 

[dazzmos]

yes they are
________________________

 

[simon_d]

yes they are

your 2 years late with that