3-phase cable calculation

[HomeCert ltd]

Hi,

A while ago I posted about my neighbours 3-phase generator etc....

So he's being running through diesel like there's no tomorrow and been talking to a local barn who have said he can take the power from his property to supply their kiln.

He's been measuring the his average usage over the last month or so, an on average his kiln uses 12kw, so we will run a cable for a 15mw supply to side on caution.

So he wants to bury a 3-phase supply to the kiln from the barn. The barn is roughly 1000m away. I wanted to check to see if I'm calculating the cable size correctly.

15kw/400 x 1.73 = 64.9amps

So Woud that be 21.6amps Per phase?
I'm struggling to work out volt drop to determine the CSA of the cable?

Thanks

 

[Pete999]

Hi,

A while ago I posted about my neighbours 3-phase generator etc....

So he's being running through diesel like there's no tomorrow and been talking to a local barn who have said he can take the power from his property to supply their kiln.

He's been measuring the his average usage over the last month or so, an on average his kiln uses 12kw, so we will run a cable for a 15mw supply to side on caution.

So he wants to bury a 3-phase supply to the kiln from the barn. The barn is roughly 1000m away. I wanted to check to see if I'm calculating the cable size correctly.

15kw/400 x 1.73 = 64.9amps

So Woud that be 21.6amps Per phase?
I'm struggling to work out volt drop to determine the CSA of the cable?

Thanks

No

 

[HomeCert ltd]

But he can't be using 12kw per phase, so wouldn't that be the total split between phases?

His current kiln is supplied via a 20kw diesel generator. When I was there before Christmas I measured the current on each phase at that point of time and it was only like 7-8kw between all 3.

 

[snowhead]

The barn is roughly 1000m away. I wanted to check to see if I'm calculating the cable size correctly.

To put it another way,, 1 kilometer away.

Put 25amps and 100mtrs into this calculator and note the result.
Then change it to 1000mtrs, the result may surprise (or not);

Cleveland Cable Calculator - http://www.clevelandcable.com/calculator.php

 

[HomeCert ltd]

I was thinking round 16mm to handle the voltdrop. So what I wanted to check, the current requirements its asking for, I'm guessing that's 21.6amps rather than 64.9amps. As there's a massive difference between 25mm and 95mm!

 

[Leesparkykent]

I was thinking round 16mm to handle the voltdrop. So what I wanted to check, the current requirements its asking for, I'm guessing that's 21.6amps rather than 64.9amps. As there's a massive difference between 25mm and 95mm!

Good luck with the 16mm. Your more likely looking at around 95mm

 

[HomeCert ltd]

So it is 64.9amps, 95mm. Wow. Guessing this isn't a viable option.

 

[Andy-1960]

I was thinking round 16mm to handle the voltdrop. So what I wanted to check, the current requirements its asking for, I'm guessing that's 21.6amps rather than 64.9amps. As there's a massive difference between 25mm and 95mm!

16mm is nowhere near big enough to handle the volt drop of a 1km cable route. Then the next problem will be how you overcome the earth loop impedance issue.
I suggest you do some calculations to size the cable correctly and then look at how you are going to protect said cable against an earth fault.

On a positive note, I do think you installing a 15MW supply (as per your original post) is a bit overkill!

 

[HomeCert ltd]

95mm at £31 per meter, x 1000m is £31k for cable. Might be cheaper to contact U.K. Power networks for their own supply.

 

[Leesparkykent]

So it is 64.9amps, 95mm. Wow. Guessing this isn't a viable option.

The total load is 15KW and you have three phases....so about 21A per phase.