500m Cable run...

[Energetic]

Have been asked to look at a 500m run for a 10kW and 50kW PV options. I'm getting catastrophic VD losses on the 50kW in AC TPN on 35mm SWA. For the 50kw you’re looking at 13% losses with 35mm. That’s over 6kw lost.

The losses on the 10kw AC TPN are 1.5% on 35mm which i'd consider on that basis but thats still £5K ish of cable which looks pretty damn pricey for 10k of PV.

Any ideas?

 

[BruceB]

What about swapping ac losses for dc losses?

 

[Energetic]

I'm looking at that now, the higher voltage helps but they want distribution circuits there ideally.

 

[Marvo]

On long line networks we sometimes use a pair of 1kV volt drop compensation transformers. Step up at source and the step down at the load end is wound to compensate for the volt drop so the transformers aren't identical ratios. Also at 1kV there's no need for specialised HV cabling etc. There's obviously a price point where these become viable determined by the cable length but they've bee viable for us on 500m runs before. I only have info on the locally made units we use but I'll see if I can find you a UK link for some later when I have time.

 

[jason121]

Look for cable size selection on another thread a few weeks back. Suggestions were based on G59 relay

 

[Energetic]

On long line networks we sometimes use a pair of 1kV volt drop compensation transformers. Step up at source and the step down at the load end is wound to compensate for the volt drop so the transformers aren't identical ratios. Also at 1kV there's no need for specialised HV cabling etc. There's obviously a price point where these become viable determined by the cable length but they've bee viable for us on 500m runs before. I only have info on the locally made units we use but I'll see if I can find you a UK link for some later when I have time.

Hi Marvo,

This idea appeals greatly to them. I have found a UK supplier... waiting to hear the price...

 

[Marvo]

Glad you found a supplier and good luck, I hope it gives you a price advantage. I know it's rude to ask the price but I'd be interested to know what you get quoted in the UK for a pair.

 

[Gavin A]

Hi Marvo,

This idea appeals greatly to them. I have found a UK supplier... waiting to hear the price...

will you need to fit a G59 relay at the grid end of this arrangement?

Just trying to get my head around how it would work in terms of the solar inverters voltage, protection settings etc.

 

[Energetic]

Likewise. If the price makes it a viable option I'll speak to the DNO to see what their thoughts are, also a few inverter manufacturers. Interesting exercise if nothing else...

 

[JD6400]

Hi Energetic , would you mind posting up the contact details of the suppliers for those transformers ?
I have looked into this a couple of times but as of yet I have not found a viable UK supplier .
We seem to install more than our fair share of lengthy sub mains and I would really appreciate the contact .

Many thanks

Dave

 

[Energetic]

Hi All,

Some info on the transformers:
Carroll & Meynell are the guys to speak to based in Stockton-On-Tees:

Carroll & Meynell Transformers - Home page

They were very helpful and knowledgeable but it looks like even the 1kV system isn't going to be enough. They do a 3kV system that would get the current down to 10A.

Not sure i'm allowed to play around with MV though. Anyone know about this?

So WDP are looking into the G59 issues and now i have to find a source of 3kV cable and switchgear.

Or I need to learn how to say 'No sir it's just not possible.' But i hate saying that...

 

[Marvo]

...........Or I need to learn how to say 'No sir it's just not possible.' But i hate saying that...

We prefer to say anythings possible with the right sub-contractor working for us.

 

[Marvo]

Just wondered how you got on with this. Did you end up using a 1kV or a 3kV transformer setup and if you did has it save costs compared to the large cable size?