Medium Voltage Line loss fraction and number of transformers

[Skyler V]

If I know the overall MV loss fraction of my MV collection system, how should I enter this into PVsyst? 

An automatic calculation in PVsyst has made me question this.

If I enter 1% loss at 1 transformer, and then adjust the number of transformers to 10, the PVsyst automatically distributes that loss equally between the new number of transformers (see screenshots).

My understanding is that if a cable is defined and total MV cable length remains constant, increasing the number of transformers effectively shortens the length of cable associated with each transformer. This suggests that if I know my total loss is 1%, I should enter: total loss / # transformers = 1%/10 = 0.1%.

Is this the correct way to think about this?

For reference, my system has multiple MV collection circuits of daisy chained transformers. I believe PVsyst refers to this as "transformer cascade"

[André Mermoud]

Yes indeed, your configuration corresponds to what is named "connexion in cascade" in the help.

This configuration is not implemented in PVsyst in the present time. PVsyst considers that each transformer is connected individually to the HV transformer input, or injection point.  

You should evaluate externally  the global loss of your configuration, and define lines at the output of each transformer in order to get the same energy loss.

The help https://www.pvsyst.com/help/project-design/array-and-system-losses/ohmic-losses/transfo-in-cascade.html?h=transf  explains how to calculate this loss in a rather general way.

Now in your simple exemple where you decide "a priori" that you want to define a loss of 1%, you can simply suppose that for each transformer, you define lines for a loss of 1%.

NB: You should not define 1%/10 transfos = 0.1%, as this percentage is referred to the power of each transformer.