Metal resistivity

The resistivity of wiring metals is dependent on the temperature, which can widely vary due to dissipating currents. The wire temperature is also depending on the installation method (ducts, neighbours conductors, exposure to the sun, etc), which is not quite well controlled in PVsyst.

The basic value is specified for pure metal, at 20°C :


*Copper*:	Rho = 1.68 E-8 * (1 + 0.0039 * (Temp - 20) [°C] ) [Ohm·m]
Default value:	Temp = 50°C => Rho[50°C] = 1.88 E-8 [Ohm·m]
	= 18.8 [mOhm·mm²/m]


*Aluminium*:	Rho = 2.82 E-8 * (1 + 0.0039 * (Temp - 20) [°C] ) [Ohm·m]
Default value:	Temp = 50°C => Rho[50°C] = 3.15 E-8 [Ohm·m]
	= 31.5 [mOhm·mm²/m]

However the resistivity may increase when the metal is not quite pure, we don't know the real resistivity of industrial wires.

These values are evaluated at 50°C, the default in PVsyst.

You have the opportunity of modifying these values, which are specified in the advanced parameters, topic "System design parameters").. In the main menu, please use Settings > Edit Hidden parameters. In the category "System design parameters losses, shadings", you will find the items "Copper Resistivity" and "Aluminium resistivity".

Wire resistance

The resistance of one wire is calculated as:

Resistance [mOhm] = Rho [mOhm·mm²/m] * Wire length [m] / Section [mm²]

In the wiring definitions of PVsyst:

The tool for the PV array resistance (DC side) supposes defining the wire lengths as the total wire as "seen" from the input of the inverter (back-and-forth)
On the AC side, there may be 2 or 3 wires, depending on mono or tri-phased circuits. Here the considered length is the distance between concerned devices, i.e. the length of one wire.

In the AC side dialog, you can choose the metal (copper or aluminium) for each circuit.

In the DC side, this choice is available by the button Wire, where you can also define a price for the wires.