Volt drop question

[oliver s]

Hi all

Just had an enquiry for 50 kw ground mounted PV system, the proposed system is to be connected to a three phase supply In an industrial unit, the ground mounted array will be approx. 200mtrs away from the unit.
The inverters and generation meters are to be mounted next to the array.(standard meters will be in the unit)
Is the usual 4% volt drop acceptable for the ac supply or would it be calculated at 1%

Thanks in advance

 

[SolarCity]

It's a judgement call, I would say.

What is the grid voltage currently? If it is low then you can maybe afford to let the 1% rule slip. You do risk the possibility of problems in the future however if the grid voltage rises.

Unfortunately, as you have probably noticed, the cable size required to achieve a <1% VD are horrific at that sort of length.

 

[oliver s]

Thanks Solar city ive not yet measured the voltage only initial enquiry but yes the cable size by a quick calc would be a 300mm!! at 1% and even at 4% a 95mm

Does that sound right?

 

[davesparks]

Try calculating for multiple cables in parallel, you should be able to get the overall size down and get a low voltage drop.

 

[Earthstore]

Or run the DC back to the building and mount the inverters there, as I understand the voltage drop for high voltage DC is lower than AC and you will not then have the problems with the inverters shutting down because they have gone over voltage.

There must be a reason why the UK buys power from France in DC and we have an inverter station in Kent, Google it, it is an interesting read.