Selection and calculation of photovoltaic cables

Selection and calculation of photovoltaic cables

The selection of cable cross-section should meet the requirements of allowable temperature rise, voltage loss, mechanical strength, etc. The DC system cable should be selected based on the long-term allowable current carrying capacity of the cable and verified according to the allowable voltage drop of the cable. The calculation formula is as follows:

According to the long-term allowable current carrying capacity of the cable: Ipc>=Ical

Allowable voltage drop per circuit: Scac=P ˙ 2LIca/△ Up

In the equation:

Ipc- allowable current carrying capacity of the cable, A;

Ica- calculated current, A;

Ical- Calculated current for long-term operation of the circuit, A;

Scac- Calculated cross-section of the cable, mm ²；

P- Resistance coefficient, copper conductor P=0.0184 Ω ˙ Mm ²/ m. Aluminum conductor P=0.0315 Ω ˙ Mm ²/ M;

L- Cable length, m;

△ Up- allowable voltage drop of the circuit, V.

Attention: The current carrying capacity of a cable is greatly affected by the laying method and surrounding environment, and the voltage drop of the cable is greatly affected by the length of the cable. Therefore, the current carrying capacity can be considered as a value that cannot be exceeded during long-term operation of the cable. It is best to select a cable based on 70% to 80% of the current carrying capacity to effectively ensure the temperature rise and voltage drop of the line.