Power distribution limits

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Well, the grid more or less spans the continent, so I'd say a very long distance.

I think there are others here who can give you a more meaningful answer than I.
 
Well, it depends on your definition of "far". It also depends on "how much".

There are one or two enemies of long distance power transmission.

The first is resistance. Every real cable has resistance, and if you pass electricity through the cable, the resistance losses of the cable will convert some of that power to heat. The longer, or thinner the cable, and the more current (amps) it carries, the greater the losses, mathematically these are worked out as I*I*R, writting I2R, pronounces eye squared are.. So the losses go up lineraly by distance, and by the square of current. Thus you want to carry the minumum current possible, which means you use higher voltages and lower currents to carry the same power.

The second enemy is uniuqe to AC transmission and is capacitance. This is a loss that goes up linearly by the length of the cable, and if the cable is long enough then no power comes out the other end; it is all lost. The amount of capacitance depends on the cable and its installation method, but it is noteworthy that undersea cables are much worse than overhead cables. The limit on an AC undersea cable is about 30 miles from memory; after that all the power is lost.

The cure for this problem is DC transmission (HVDC) which can carry power thousands of miles with no capacitive losses. But you still get I2R losses.
 
A rule of thumb as regards the maximum distance over which power can be transmitted, is that the distance in miles should not exceed the voltage in KV.

240 volts=0.24KV= About a qaurter of a mile
11KV= about 11 miles.

Much greater distances are entirely possible, but tend to be uneconomic unless the load is very small.
For significant loads, if the distance in miles exceeds the voltage in KV, then it usually worth useing a higher voltage, or moving the load or the power source closer together.

USA type house services seldom exceed a qaurter mile from the transformer, some do certainly, and these require heavy expensive cables and tend to suffer from voltage drop.

Here in the UK local distribution is often at 11KV, and such lines are normally less than 10 miles.
 
If you want to stay with an AC line it will have to be compensated. With the DC transmission there is the added cost of the convertor stations at both end.
 
hardworkingstiff said:
Is there a pratical limitation as to how far electricity can be transmitted? If so, anyone care to give the Readers Digest version of what it is and why?

Thanks,
Click to expand...

It's an old folks story: it DEPENDS.:grin:

Economic decision, based on the price of the transmission and conversion equipment cost.

Some rules of tumbs were tossed out on the recent copper fluctuations.;)
 
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