AC Ohmic losses calculation

[AndrewChristoph]

Dear André!

We are working on some large projects (bigger than 1MW), where we need to make simulations on our solar plants. We just started using PVsyst and I think we are getting better and better at it, but there are some questions which we cannot answer after trying many scenarios.

Our biggest problem now is that we do not really know how does the software calculate the AC ohmic losses for the whole system. We need to give the total length of the wires between the transformer and the inverters, and also the total cross-section of the several AC cables. The problem is that the AC ohmic losses that are shown in the report don't match with our estimations (much bigger than the estimations). Usually between 6 and 13%.

Please let us know, if only we are overcomplicating this issue?

On the other hand, can you please tell us what is the accurate way to give the correct parameters of the AC wiring?

(For example: if we have 42 inverters each with 50mm2 cables to the transformer, then we need ~2100mm2 cross-section totally, but we need to calculate with 42*100m length?)

I am looking forward to your response.

Yours sincerely,

Andrew and Christopher