Tritec

Dears, I'm simulating a PV plant .This plant has 3 inverters, each inverter has 8 string box and each string boxs has 24 string. I wish calculate ohmic losses for the array with the Detailed computation option, in PVsyst, I need to put average lenght in meters per circuit. My question is, what I consider as a circuit? All the plant, one inversor or other? Thanks. Diego