loss parameters

[FOFONE]

 

Hello to all, 
I am sizing a 10MWp solar plant with PVsyst. At the level of the detailed loss parameters, more precisely the thermal losses, the software proposes me sections of cable going up to 2000m² between the connection box and the inverter. what I find too big.
Can you explain me that, why such a section?

[Lazare Fesnien]

The ohmic losses behave in a quadratic way with the array current:   Ploss = Rw · Iarray².

Now if the array is not operating at  STC, the wiring loss fraction   will become:

Ploss / Parray  =   Rw *  Iarray²  / (Varray * Iarray)   =  Rw * Iarray / Varray.

i.e. proportional to Iarray. This means that at half the irradiance (half the current), the wiring loss fraction  will be half, etc. Therefore the Wiring energy loss has to be evaluated at each hour of the simulation, and accumulated in terms of energy.

The final result of the Ohmic wiring loss (in terms of percentage) as shown on the loss diagram will be from this hourly energy balance. It is usually of the order of 60% of the Loss fraction specified a STC.

 

[FOFONE]

Thanks,

My question is more about the cable section, is it possible to have a section of 2000m² or more  between the junction box and the inverter?

[Lazare Fesnien]

Dear Fofone, 

Theoretically yes, after it will be privileged the multiplication of cable like 3 x 3G500

[Sampa98]

Dear,

According to the manual, it is necessary for the user to define the specific section. To ensure that your installation complies with safety standards, I recommend making a preliminary calculation of the allowable current, taking into account the grouping, temperature and channeling factors of your installation. As well as a calculation of the voltage drop generated by selectioned conductor. To obtain the factors mentioned above and the resistance and reactance of a conductor, you can use a cable catalog.

Once these calculations have been made, it is essential to identify the minimum stretch that meets both requirements. By assuming this section for the simulation, you can move forward with greater confidence in your simulation ohmic loss calculations.

However, it is important to note that if you go ahead with the project, it is crucial to check the maximum short circuit current to ensure that all safety standards are met.

Greetings,