TT Supply to Barn - LONG distance - help(?)

[s100cky]

Hi all,

Ive been to look at a project with a customer this evening. He is looking to put a 100A SPN supply into a remote barn location. He has had Western power out to look at the options, they have advised him they can pull a supply off a overhead line to give him a SPN 100A head.

The problem is that this is 415(ish) meters away from the Barn.

Now this isn't my usual bag, so sorry for the ignorance - and the books are not with me this evening, but I believe the options are as follows:

• Put a LV TT submain to the Barn, via a trench, which would be a massive cable due to VD.
• Get western power / others to install a HV radial from the overhead line to a small HV-LV transformer at the Barn. Reducing the size of cable and possibly the project cost?

Im sure I have overlooked some other options, but this one I cant get out of my head.

If anyone has done a project similar id be very interested to hear about it.

Regards all....

 

[Leesparkykent]

Hi all,

Ive been to look at a project with a customer this evening. He is looking to put a 100A SPN supply into a remote barn location. He has had Western power out to look at the options, they have advised him they can pull a supply off a overhead line to give him a SPN 100A head.

The problem is that this is 415(ish) meters away from the Barn.

Now this isn't my usual bag, so sorry for the ignorance - and the books are not with me this evening, but I believe the options are as follows:

• Put a LV TT submain to the Barn, via a trench, which would be a massive cable due to VD.
• Get western power / others to install a HV radial from the overhead line to a small HV-LV transformer at the Barn. Reducing the size of cable and possibly the project cost?

Im sure I have overlooked some other options, but this one I cant get out of my head.

If anyone has done a project similar id be very interested to hear about it.

Regards all....

how far away Is an existing supply to pick up from?

 

[s100cky]

Theres a TPN supply in a a barn near the over head head lines (450m ish) Not sure of condition or capacity
and the overhead line transformer and suggested position of meter enclosure by W.P is 415m

 

[bigspark17]

I highly doubt western power putting overhead lines in closer to your barn will reduce overall project cost.!

 

[mattg4321]

We recently did a job where UKPN 'moved' their supply from a cabinet at the bottom of the clients field, to the house itself. A distance of around 350m. The transformer stayed in the original position - at the bottom of the field. Builder did ground works for them. Cost around £16k

 

[s100cky]

Thanks mattG! I suspected that might be the case. I wonder the size and type of cable used for the move. I can't help but think the viability of the project goes out the window with it die to cost and cable size.

Bigspark17 - I was thinking more of UKPN trenching a HV supply to the barn, not sure of the requirements of this however.

 

[JD6400]

Have a look at the price for the cable first , before giving it up as a bad job .
Almost always you are far cheaper gettting the DNO just on to the property and then looking at the rest of the run yourself.
We have one at the moment for a isolated new build on one of the estates that we look after , the run is 550m from the nearest source and a 2c 120mm ,just cost us £6149 + the dreaded . Now I know that is not great , but it is better than the £ 78000 + vat from the DNO !

 

[davesparks]

• Put a LV TT submain to the Barn, via a trench, which would be a massive cable due to VD.
  
  
  ..

• 
  
  
  Not necessarily a massive cable as you will quite possibly find that two or three smaller cables in parallel will be better for this.

 

[s100cky]

Have a look at the price for the cable first , before giving it up as a bad job .
Almost always you are far cheaper gettting the DNO just on to the property and then looking at the rest of the run yourself.
We have one at the moment for a isolated new build on one of the estates that we look after , the run is 550m from the nearest source and a 2c 120mm ,just cost us £6149 + the dreaded . Now I know that is not great , but it is better than the £ 78000 + vat from the DNO !

Thanks fir the input JD4600! Can i ask what calc's you done for the volt drop, when i done some very basic calc's i was getting a 4x120c in parallel to compensate for the VD. I was using a load of 80A (rough guide) and a run of 415m buried in soil at 20'c.

Thanks for the help so far.

 

[gaz101]

Thanks fir the input JD4600! Can i ask what calc's you done for the volt drop, when i done some very basic calc's i was getting a 4x120c in parallel to compensate for the VD. I was using a load of 80A (rough guide) and a run of 415m buried in soil at 20'c.

Thanks for the help so far.

Multicore 90°C Armoured Thermosetting Insulated Cables

Tables Apply to: H6942XL, H6943XL, H6944XL, H6945XL, Tuff Sheath,
Voltage: 230V
Load:18.4kW / 80A
Length:415m
Method of Installationirect in ground or in ducting in ground
Cable Size: 185mm²

Looks cheaper depending on over current protective device

doncaster cable web calculator

gaz

 

[s100cky]

Hi Gaz101,

Thanks for that, I think the issue with the 185 is that is does not allow for any further voltage drop from a CU within the new barn. It will be smallish dwelling but will have lighting, power etc. So i think a further allowance for VD after the CU pushes the cable size to 240mm, which i believe from a quick tinker on Amtech (GOSH!) i can have 120mm 4c in parallel. (2 cores for L + N) within the cable.

 

[hightower]

I've just been having a play with cable sizing for my own learning, (I've probably overlooked something massive) but I get you need a figure of 0.166mV/A/m or less for a 100A load over 415m - so according to the BRB that'll be 300mm cable - however, I'm happy to be shown the error of my working as I'm sure I've overlooked something to be taken in to consideration on larger runs like this.

Also, in table 4D4B (BRB) the columns split down to have an R, X, and Z column - but I can't find any notes on what this means. Can somebody enlighten me?

 

[JD6400]

Thanks fir the input JD4600! Can i ask what calc's you done for the volt drop, when i done some very basic calc's i was getting a 4x120c in parallel to compensate for the VD. I was using a load of 80A (rough guide) and a run of 415m buried in soil at 20'c.

Thanks for the help so far.

60a on our Amtec sizing software .
As davesparks says you should be pleasantly surprised by looking at paralleling , the only reason we did not on this one was due to a constraint on how we will mole it past a brook that is bang in the middle of our run !

 

[GEOFF S]

Hi

80 amps per phase seems like a lot for a barn?

Anyhow if its pretty much balanced then 120mm should suffice.

Cheers

 

[davesparks]

Multicore 90°C Armoured Thermosetting Insulated Cables

Tables Apply to: H6942XL, H6943XL, H6944XL, H6945XL, Tuff Sheath,
Voltage: 230V
Load:18.4kW / 80A
Length:415m
Method of Installationirect in ground or in ducting in ground
Cable Size: 185mm²

Looks cheaper depending on over current protective device

doncaster cable web calculator

gaz

Did you de-rate for 70 degree operation?

 

[ipf]

I've just been having a play with cable sizing for my own learning, (I've probably overlooked something massive) but I get you need a figure of 0.166mV/A/m or less for a 100A load over 415m - so according to the BRB that'll be 300mm cable - however, I'm happy to be shown the error of my working as I'm sure I've overlooked something to be taken in to consideration on larger runs like this.

Also, in table 4D4B (BRB) the columns split down to have an R, X, and Z column - but I can't find any notes on what this means. Can somebody enlighten me?

The z is impedance value, r is the resistive component and x the reactive. Have a look at correction for load power factor and how design value is obtained.

 

[hightower]

The z is impedance value, r is the resistive component and x the reactive. Have a look at correction for load power factor and how design value is obtained.

It might be a bit over my head for now, should imagine I'll cover it next year on level 3. Thanks

 

[davesparks]

It might be a bit over my head for now, should imagine I'll cover it next year on level 3. Thanks

Possibly not unfortunately, they certainly didn't bother when I was doing level 3!
To be honest it's one of those things I have never actually fully got to grips with