Wiring Losses

1. The solar station is divided into subsystems. For the architecture of a solar station with a central inverter, where strings are connected to combiner boxes using a harness, the following subsystems are defined:

• Tracker subsystem
• Combiner box subsystem
• Inverter subsystem
• Substation subsystem

2. In each subsystem, DC losses in low-voltage wires are calculated using the following formula:

Length * Resistivity * Current * Current

Here:

* Length is the length of the conductor, including both positive and negative wires, in feet.

* Resistivity is the wire's specific resistance per linear foot, in ohm/ft. The resistivity value is taken from the NEC table for a conductor temperature of 25°C and adjusted to the operating temperature set by the user.

* Current is the current in the wires, in amps. The current in the wire is determined based on the module current under STC (Standard Test Conditions), following the rule of current addition for parallel and series connections of the current source.

3. The losses calculated in each subsystem are summed to obtain the total system losses.

4. The total system losses are divided by the DC power of the entire system, which gives the Voltage Drop for the entire system under STC conditions.