With my installation on a terrain, I have multiple orientations

[André Mermoud]

When you follow a terrain with your tables of modules (i.e. when you incline the base of your modules), the real orientation of the plane of array changes. This is especially the case with scenes imported from CAD software like  Helios3D software, PVCase, Sketchup, etc. 

See  https://forum.pvsyst.com/topic/30-with-sheds-on-a-tilted-roof-pvsyst-changes-my-orientation/#comment-30

Average orientation

Therefore, when you distribute your tables on a hill, each table will have its own orientation depending on the slope of its basis, so that you will have a distribution of orientations.

This may result in an error "You have defined fields with XX different orientations, you cannot define more than 8".

You can analyze this distribution and modify the tables that are attributed to each orientation group in the menu of the 3D scene, "Tools > Orientations Management".

For such a situation, PVsyst will use the average orientation of the distribution in each orientation group for the transposition step in the simulation.

When importing or creating a 3D model with non-uniform table orientations, PVsyst will automatically create the orientation groups according to a limit discriminating angle. This limit is specified for your project, using the button "Project's settings" ("Albedo & Settings" in older PVsyst versions), in the tab "Other limitations". For automatically getting one only average orientation, you can increase this limit, at the price of a slight loss of accuracy in the transposition calculation. If the automatic grouping of orientations is not satisfying, you can manually adjust the attribution of tables to the groups as described above.

Several Average orientations

If you decide to group the tables in several average orientations in order to have more accuracy in the transposition calculation, you should keep in mind, that in the 'System' part of PVsyst the sub-arrays are linked to a single orientation. You therefore need to make sure, that splitting the tables into several orientation groups should stay compatible with the sub-array organization of the PV system you are designing.