AC Cables for 5MWp Solar Farm

[tiennoeis]

Hello Everyone,
I just joined the forum and I have a couple of questions I would like to ask.

I will soon be involved in a very big project around 5MW and I would like to know more on the AC cable types and sizes.
I haven't seen the system layout so I don't know the exact distances, so I am looking for a very rough estimate.

As for the DC I suppose we will be using from 6mm to 10mm cables.

I am however more interested in the AC side. Are there any British Standards that have to be followed in terms of cables?
I also would like to know what kind of cables would have to be used for Low and Medium voltage? And one last question, do they ac cable runs have to be placed in pipes for a solar farm or is left to be decided by the installing company?

Any help is greatly appreciated .

 

[Gavin A]

I've not been involved in anything above 50kW myself, but presumably the cable sizing depends on the size of the inverters being used, how many inverters are being parrallelled up onto each cable, and the distances involved back to the mains connection point.

I'd assume it'll be done in sub blocks of more manageable levels, and if I were managing it I'd probably have a specialist cable pulling team doing the pulling in of the long main cable runs to the distro boards, then another team wiring the inverters from the distro boards, and running the DC cabling.

 

[tiennoeis]

I was more interested in the cables from the dist board to the g59 to the transformer and then to the point of connection to the mains(If that's the right order) . Is there a specific cable used for this purpose (SWA?).. the size of it I understand depends on the distances and for a farm like this I reckon it could go up to 300mm2 (again correct me if I'm wrong)

 

[SpitfireW'sale]

Is your enquiry out of interest or are you involved in designing the system?

 

[Worcester]

I would suggest that you get the design from the E&M and Civils designers before you start speculating, you could easily have it completely wrong. Also the project engineer with have a full ctricial path project plan already designed, so they will be dictating your work sequence. All sorts of facors come into play, panel inverters, string inverters, central inverters, how many? locations? run lengths? Presumably it's connecting to 11KV or is it a 33kV connection? Where are the voltage drop calulations done from?

As I say there are far too many variables, and you could spend weeks speculating. Get the E&M schematics and the Civils physical drawings and the BoM and you'll have all your answers in seconds.

If you are involved in the design then theses are fundamental questions that you should know like the back of your hand, there are too many environmental considerations to take into account to say which type of cable at this point. - Presumably you know where to find that information anyway....

 

[tiennoeis]

No I am not designing this one. I just want to understand a bit more about solar farms as I have only been working on commercial roofs up to 250kWp.

 

[dimcha]

Solar farm is just another electrical installation. IEE Wiring Regulations 17th Edition is the answer to your question in terms of British Standards. all AC cables must be armoured cables as long as they are buried in the ground.

DNO is responsible for the 11kV cable. I think you are not authorised to do anything on the MV side. refer to your local DNO for more info regarding MV.