This article mainly introduces the cable selection and design methods in photovoltaic systems, covering factors to be considered when selecting cables in photovoltaic systems, how to select appropriate cables in different environments, and the principles that should be followed in the design of cable size and specifications.
The following factors should be considered when selecting cables in a photovoltaic system:
1. The insulation performance of the cable;
2. The heat resistance and flame retardant properties of the cable;
3. Moisture and light protection for cables;
4. Cable laying method;
5. Cable core type (copper core, aluminum core);
6. Cable size and specifications.
II. The connections between different components in a photovoltaic system require different cables due to varying environments and requirements. The technical requirements for each connection are listed below:
1) The connection between components must be UL tested, heat resistant to 90°C, acid resistant, chemical resistant, moisture resistant, and sun resistant.
2) The wiring between the battery and the inverter can use UL-tested multi-strand flexible wire or UL-tested welding machine cable.
3) Connections within and between the square formations can be exposed to the open or buried underground, requiring protection from moisture and direct sunlight. Piping installation is recommended; the conduits must be heat-resistant up to 90℃.
4) For indoor wiring (dry environment), a shorter DC cable can be used.
III. The design of cable size and specifications must follow these principles:
1) For short-distance DC connections from the battery to indoor equipment, the rated current of the cable should be 1.25 times the calculated continuous current of the cable.
2) For the connections within and between the arrays, the rated current of the selected cable is 1.56 times the calculated maximum continuous current in the cable.
3) For AC load connections, the rated current of the selected cable should be 1.25 times the maximum continuous current in the calculated cable.
4) For the inverter connection, the rated current of the selected cable is 1.25 times the maximum continuous current in the calculated cable.
5) Consider the effect of temperature on cable performance.
6) Consider that the voltage drop should not exceed 2%.
7) The appropriate cable diameter is selected based on two factors: current intensity and circuit voltage drop. The calculation formula is:
Line loss = Current × Circuit bus length × Cable voltage factor (available from the cable manufacturer)
