The photovoltaic cable (solar cable) is often an underestimated element of the entire installation, and yet the functionality of the photovoltaic set depends on it. This is the connection that brings the energy produced from the panels to the inverter, and although their price is only a fraction of the costs of the entire system, many investors see an opportunity to save here. Is it right? Which photovoltaic cable should I choose? What cross-section of a photovoltaic cable will be optimal?
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Characteristics of the photovoltaic cable
The importance of solar cables is proven by the fact that the problem with turning off photovoltaics at high voltage may result from the incorrect selection of the cross-sections of electrical cables. The features that a photovoltaic cable should have are described in the PN EN 50618:2015-03 standard.
A photovoltaic cable should be made of materials resistant to UV radiation, moisture, weather conditions and temperature fluctuations. In the event of a fire, the photovoltaic cable should not generate smoke or toxic gases, which could pose a threat to the health of people participating in the firefighting operation (standards including UNE-EN 60754-2 and IEC 60754-2). It should be resistant to mechanical damage. The low coefficient of electrical resistance minimizes energy loss when current flows from the panels to the inverter. It is also important that the photovoltaic cable is flexible because it is easier to shape and lay it on various surfaces;
Photovoltaic installations may be located in industrial areas where potential chemical pollution occurs. It is assumed that under normal operating conditions, PV cables should last at least 25 years. The solar cable should be equipped with appropriate markings confirming compliance with norms and standards for photovoltaic installations. Certificates such as TUV, UL, CE confirm compliance with specific quality standards.
The selection of the cross-section of a photovoltaic cable should take into account the power of the panels, the distance between the panels and the inverter and the parameters of the current that will flow through the cable. A cross-section that is too small may result in significant energy losses, while a cross-section that is too large will increase the overall cost of the installation.
When selecting a cable, you also need to remember its length. This should be selected taking into account the distance between the panels and the inverter. A cable that is too long may cause voltage drops, and a cable that is too short may prevent proper connection.
Which cable for 10 kW photovoltaics?
For installations from 10 to 15 kW, it is recommended to use a cable with a cross-section of 6 mm². This involves the need to limit the loss, which is considered acceptable for photovoltaics at 1%. Installations with a power of 10 kW or more should be made using, for example, the Lapp H1Z2Z2-K 1 × 6 WH/BK solar cable .
Which cable for 6 kW photovoltaics?
With an inverter power of up to 7.5 kW , a Lapp H1Z2Z2-K 1 × 4 WH/BK solar cable should be used, the rated conductor cross-section of which will be 4 mm². This will reduce installation costs while maintaining optimal energy production parameters.
5 kW photovoltaic cable
When determining the cable cross-section yourself, it is worth using a relatively simple formula:
Wire cross section = (I * n) / U * k * 0.01
The result is always given in mm².
Meaning of symbols:
n – total length of the circuit in meters;
I – IMpp current under NOCT conditions (ampere);
U – voltage of the UMPP circuit under NOCT conditions (volts);
k – conductivity (conductivity) of the material from which the cable is made;
0.01 – permissible losses on circuits (assumed 1%).
In the case of 5 kW photovoltaics , the Lapp H1Z2Z2-K 1 × 4 WH/BK solar cable will be perfect. with a core cross-section of 4 mm².
4 kW photovoltaic cable
Similarly to the above case, there is no point in investing in a more expensive cable with a larger cross-section. A 4 kW installation will function perfectly using a cable for photovoltaic installations Solarflex - X PV1-F 1 × 4 with a cross-section of 4 mm².
It is best to entrust the selection of a photovoltaic cable and the related calculations to a person with knowledge and competences in the field of photovoltaic installations. Otherwise, there is a risk of underestimating the system's efficiency, as well as a threat to the safety of users of the PV installation.