How much current safe for 30m extension?

I am in the UK (so mains voltage is about 230V or 240V).
I have a reel of main extension cable made of 3-core 1.0 mm^2 wire
rated at 10 Amps. So the nominal power rating would be about 2,400 Watts. (Link to tech reference for the cable is below.)
Presumably the current carrying capacity or power delivery capability of the unwound 30m length unwound is going to be a bit less than 10 Amps/2,400 Watts due to losses along the length of the cable itself.
Is the reduction in current/power carrying capability significant? If so, then is there a rough guideline figure for available current/power which I can use?
If I take *two* of these 30m reels then I can join them with the standard UK 13 Amp plug and socket supplied on the reels. This gives me an overall length of 60m. Taking into account losses, what would be the current carrying or power delivery carrying capability of the 60m length if all the 60m cable is unwound?
Thanks for any info. Sammo
Technical reference for the cable is HAR type H05VV-F3 x 1.00 mm2 - (details at http://tinyurl.com/7y5xx )
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

It's always going to be safe, as it's got a fuse.
Ok... Copper has a resistivity of 0.7*10^-8 ohms/meter.
Or, for a 1mm^2 wire, 0.7*10^-2 ohms/meter. Or for 2 wires, 1.4*10^-2 ohms. Or for 60m, 8.4*10^-1 ohms, or .84 ohms. At 10A, 8.4V, or heating by 84W. If at the plug end is 240V, at the socket end will be 232V, which is (232^2/240^2)= .93444444444444444444
So, you lose 7% of the power for a heater, for example.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Doh, 1.7.

1.7*10^-2
3.4*10^-2
2 ohms.
At 10A, 20V, or the cable heating by 200W. If at the plug end is 240V, at the socket end will be 220V, which is (220^2/240^2)= .84027777777777777777
So, you lose 16% of the power for a heater, for example.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote:

Plus the resistance on the two connections. Not sure whether the earth fault loop impedance is still OK...
--
Bob Eager
begin a new life...dump Windows!
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

I took that into account. (but misremembered the resistivity of copper) See other post for correction.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 12 Feb 2005, Ian Stirling wrote:

What is earth fault loop impedance?
(Yup, I have tried Google!)
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Darcy B wrote:

It is the sum total of the resistances af all the wiring in the path to earth or ground. It is significant because should a major fault occur (like a wire falls inside an appliance and shorts to the casework, or you cut through an extension lead), the earth fault loop impedance will place a limit on the maximum current that can flow to earth.
Ideally this fault current wants to be large, so that it causes the protective device (fuse / breaker) to open quickly. We have regulations in the UK that require a circuit with socket outlets to disconnect in under 0.4 secs in these situations.
The fault loop impedance is also dictated by the impedance of the earth provided at the supply where it comes into the house. In the UK there are three common ways the power company can provide the supply - with two of them (known as TN-C and TN-C-S (aka PME)) the supplier provides a good earth (i.e. typically well under 1 ohm) which when used with suitable fusing and circuit breakers should result in good disconnection times in most cases. However if you add long circuits with undersized earth conductors (i.e. big extension lead for example!), then the impedance creeps up and lowers the fault current that could lead to much greater electrocution risk. The third type of supply common over here does not supply an earth at all (this is typical for power fed via overhead wires - typically into rural locations), and relies on a local earth rod that is staked into the ground. These tend to give much higher resistance earths and hence you can no longer rely on them to allow enough fault current to flow, so the whole installation must be protected by additional Residual Current Device circuit breakers (RCDs) to detect any leakage from the circuit and cut off the power that way. (RCDs are also mandatory here for all socket circuits that may potentialy feed portable equipment that could be used outside).
There is some more info here:
http://www.tlc-direct.co.uk/Book/5.1.1.htm
--
Cheers,

John.

/=================================================================\
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

IIRC, 1mm flex will just about make the test at 30 metres.
We use a multi-core cable to feed a floor monitor on location filming which has mains, video and audio. And that's about it's length. Of course if you extend it everything still 'works'. And I don't have anything to do with the H&S regs testing. ;-)
--
*Wrinkled was not one of the things I wanted to be when I grew up

Dave Plowman snipped-for-privacy@davenoise.co.uk London SW
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Yeah, true. You 220VAC and 240VAC guys think you got it bad, we have four times as much of a problem here in 120VAC land. ;-)
Those poor souls that put a hundred feet or so of 18GA (about 1mm sq) extension cord on their weed wackers soon find that not only does it run slow, but the motor overheats. So we have extension cords that are 16 or 14 gauge, and can handle the extra current. But people are too cheap to pay double for the heavy duty extension cord, so they end up eating their money up in burned out motors.
And then when they get tired of doing that, they go out and buy a weed wacker with the gas engine. This is on the end of a long pole, so the engine is right up next to their face, so they go deaf from all the engine noise. And they put the weed wacker in the garage, where the gas from the tank runs out and catches on fire!

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Sat, 12 Feb 2005 10:51:00 -0800, "Watson A.Name - \"Watt Sun, the Dark

Web: http://www.oldengine.org/members/diesel
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
"Peter A Forbes" wrote | >Those poor souls that put a hundred feet or so of 18GA (about 1mm sq) | >extension cord on their weed wackers
It's a different language isn't it :-)
| >soon find that not only does it run slow, but the motor overheats. | >So we have extension cords that are 16 or 14 gauge, and can | > handle the extra current. But people are too cheap to pay double | > for the heavy duty extension cord, so they end up eating | >their money up in burned out motors. | Why use anything as small as 1mm sq cable???
If it's in Wall-mart, they'll buy it.
Owain
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Dunno where you'd get 4mm flex, but you'd never get it to fit a 13 amp plug. 2.5mm is the limit, and not all plugs will have a cord grip suitable.
--
*If a thing is worth doing, wouldn't it have been done already?

Dave Plowman snipped-for-privacy@davenoise.co.uk London SW
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Dave Plowman (News) wrote:

RS for one, see stock no. 250-1410.

Actually 1.25 mm^2 is the limit - in the sense that it's the largest size that BS 1363 requires a plug to accept. Nevertheless _most_ plugs will accept 1.5 mm^2 without too much difficulty and _some_ will accept 2.5 mm^2.
--
Andy

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

plugs
accept
I don't know about the UK, but in the U.S. most decent plugs come with three large headed screws that have a square washer under them, with one edge of the washer hanging over the edge of the brass pin, so it retains the copper wire. So if you can unscrew the screw 3/16" (5mm) and get the copper strands in there and screw it down, then it would hold almost that big a conductor. Of course getting it all thru the hole in the cord grip is another matter..

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Sun, 13 Feb 2005 17:49:42 UTC, "Watson A.Name - \"Watt Sun, the Dark

Some earlier plugs were like that. These days, there is a hole in the end of the pin, and a grubscrew into a threaded hole at right angles that clamps the wire. Remember the wire is thinner over here.
And of course, nearly all of our plugs have fuses in them. A 15A breaker is not too good at protecting a 5A flexible cable to an appliance.
--
Bob Eager
begin a new life...dump Windows!
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Right. Didn't know chapter and verse.
Our location sparks use 2.5mm TRS for most uses - and as many things may have to plug into a house supply at some point, use 13 amp adaptor leads to feed theirs. Think the 13 amp plugs they use are Duraplugs
--
*A chicken crossing the road is poultry in motion.*

Dave Plowman snipped-for-privacy@davenoise.co.uk London SW
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
cable is not that expensive, it's copper after all.I can see in an invoice that I paid 28 cents a meter for a 3G1.5 mm^2 A05VV-U cable.A 2.5 mm^2 conductor, single core, which we generally use to connect washing machines, costs 9 cents a meter .Or 6 mm^2, for ranges, 22 cents a meter.Why don't you ask an electrician to construct you an extra heavy duty extension cable, with industrial-grade plugs?I did in college, when doing my Practicum, for a high-temperature oven, three-phase, 25A, which plug tended to overheat.Cost was negligent.
-- Tzortzakakis Dimitri?s major in electrical engineering, freelance electrician FH von Iraklion-Kreta, freiberuflicher Elektriker dimtzort AT otenet DOT gr

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

invoice
machines,
don't you

cable,
for a

overheat.Cost
Negligent! Hah-hah-hah-hah!

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
in message

One question to somebody presumably residing in the western colonies.
What's a "weed wacker" ?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Polytechforum.com is a website by engineers for engineers. It is not affiliated with any of manufacturers or vendors discussed here. All logos and trade names are the property of their respective owners.