ECN Forum Forums General Topics of the Trade Non-US Electrical Systems & Trades Cheapest possible cable?

British regs. allow a 4% voltage drop, but that's from the supply terminals at the service entrance to the farthest outlet.

Bearing in mind that at these currents the voltage drop on the house cables is going to be negligible, if we extended this to allow 4% from transformer to point of utilization, it would probably still be within tolerance -- Just!


[This message has been edited by pauluk (edited 11-04-2003).]

My price comparison was pretty pointless as I forgot the copper equivalent.

A 1.5 mm2 Cu wire is about 50% more expensive than the 2.5 mm2 Al. If you compare 16 mm2 Cu vs. 25 mm2 Al, it's 100% more expensive. The difference will be smaller if you compare cables with an outer sheat, since the insulation adds to the cost.

C-H,
I'd go along with David on the use of Aluminium wire as a Service Drop.
Aluminium has a habit of suffering from Metal Fatigue, that's why when it is used as an O/Head Line between poles, it normally has a Steel cores in the middle of the strands, to give the AL some mechanical support.

C-H,
Just a small question.
Why go Overhead?, if you don't have to.
stringing wires through conduit shouldn't take that much and I'm sure that you would have more than enough help to dig the trenches.
Just a thought, but you could have fused tap-off points at each house.
With next to no loading on the wires, you wouldn't even have to de-rate the conductors.

Ragnar,
I hear you on the use of steel as a Conductor of Electricity.
We had a situation over here, where we installed a whole heap of Designer 12V Halogens on this big, cumbersome frame to light a shop display.
We had 3 Xformers to supply the current and when we turned the thing on, the light at the start of the series was bright, but the rest of them got dimmer as the system progressed down the stainless steel rods.
One thing that you have to realise about steel manufacture, is the fact that a big part of Steel is Nickel and a certain amount of Chromium, to give it it's Tensile strength.
But, what are the elements of a heater made of?.

Er.... Nichrome wire!

On the your steel frame lighting system, did you think about running one supply conductor to each end of the frame? That way the overall resistance would be the same to each light.

Trumpy,

I think you are right. It might be easier using a underground conduit than an overhead service drop with these small wires. And you're right about the derating: I could put several cables in one conduit with no problem. I rather not have the service limiter or meter too close to the customer, since people might help themselves to some free power...

After I took Mike's suggestion into consideration I came up with this: A little cabinet (pedestal if you like) in the neighbourhood fitted with a keypad and a display. On this the customer types in the pre-payment code from the voucher. If it's a metered service, there are meters and a simple computer inside which keeps track of consumption. If it's a flat rate service, there are instead simple relays which turns the power off when the customer has used up the days he has payed for, e.g. 30 days.

From this little cabinet the cables run out to the houses. This way I don't need a pre-payment terminal at each house which should save money and make it harder to bypass. Sure, someone can still break into the cabinet, but it's not very hard for the utility to find the culprit. Just follow the wires...

C-H,
How do you intend protecting (OCP) an installation like this?.
What system of supply are you looking to use?.

A friend of mine is from China. He was about 15 years old in 1970 there, and the communists there decided to ship all the city teenagers out to rural farming areas so they could learn about farming. Part of their "Cultural Revolution". But my friend from Shanghai was the only one in some rural village a few hundred miles north of North Vietnam who knew anything about electricity. The village was powered by a small hydroelectric dam and every house had one ~15W light bulb. No kilowatt-hour meters, but you'd catch flak if your house was more lit up than most others. My friend was put in charge of this power system, maintaining it and doing wiring. No NEC there! He thus didn't have to work in rice farm swamps filled with alligators or who knows what. People there had a habit of hanging their wash on the wires! I think he said it was a 220V system.