AC ohmic losses: reference power

Basically, the AC wiring losses are calculated from the resistivity, i.e. the wire length, section and metal. During simulation, at each time step, the power loss is calculated as NWire * Rwire · I².

However in practice, as a first step of the design, people often use the relative ohmic loss. This relative loss should be referred to a specified Power.

Since the version 7.2, you have the opportunity of choosing as reference:

• either PNomPV(ac), the PV array nominal power at STC (PNomPV [kWp]), multiplied by the inverter's efficiency. This is the historical choice of PVsyst before the version 7.2. |
• or PNom(Inv), the nominal output power of the inverter(s), without temperature correction. |

This choice is done for each project, in the project's settings dialog.

In the main menu Settings > Preferences > Physical models > AC Loss references, you may define the default initial value when creating a new project.