Wiring Skills for Photovoltaic Systems

I. General Circuit Division

• DC and AC Parts
  • The photovoltaic system circuit is clearly divided into a DC part and an AC part. The DC part is responsible for connecting the solar panels (components), where the direct current generated by the panels is collected. For example, in a rooftop solar installation, the cables from individual solar panels are first connected in series or parallel to form a DC string. The AC part, on the other hand, is connected to the power grid after the DC power is converted to alternating current by an inverter. In a small - scale residential system, the inverter output is then connected to the household electrical panel and eventually to the grid.
  • These two parts need to be wired separately to prevent electrical interference and ensure the safety and efficiency of the system.

II. DC Cable Management in Medium - and Large - Scale Power Plants

• Wire Numbering
  • In medium - and large - scale power plants, there are numerous DC cables. To simplify future maintenance and troubleshooting, it is crucial to firmly fix the wire number of each cable. For instance, a large - scale solar farm may have hundreds or even thousands of solar panels, each connected by a DC cable. By assigning a unique number to each cable and clearly marking it, technicians can quickly identify and trace a specific cable during maintenance or in case of a fault.
  • This can be achieved using cable markers or labels that are resistant to environmental factors such as sunlight, moisture, and temperature changes.

III. Separation of Strong and Weak Wires

• Avoiding Interference
  • Strong wires (such as power - carrying cables) and weak wires (such as signal wires) should be routed separately. Signal wires, like 485 communication wires used for data transmission between solar panels, inverters, and monitoring systems, are particularly sensitive to electromagnetic interference.
  • For example, if a 485 communication wire is routed close to a high - current DC cable, the electromagnetic field generated by the DC cable can induce noise in the communication wire, leading to data errors or communication failures. Therefore, separate conduits or cable trays should be used for strong and weak wires.

IV. Cable Protection

• Using Conduits and Cable Trays
  • When wiring a photovoltaic system, it is advisable to use conduits and cable trays. Conduits provide physical protection to the cables from mechanical damage, such as being crushed or cut. They also protect the cables from environmental factors like UV radiation, moisture, and chemicals.
  • Cable trays, on the other hand, offer a structured way to route multiple cables. They help in organizing the cables and making the installation neater. For example, in a large industrial photovoltaic installation, cable trays can be installed along the racks or structures supporting the solar panels to neatly route the cables from the panels to the inverters and other components.
  • Minimizing cable exposure is important as exposed cables are more vulnerable to damage and environmental degradation.

V. FAQ

• Q: Can I use the same conduit for DC and AC cables?
  • A: It is generally not recommended. DC and AC cables should be kept separate to avoid electromagnetic interference and ensure safety. However, if necessary, they can be installed in the same conduit under specific conditions and following strict electrical codes.
• Q: How often should I check the cable numbering in a large - scale power plant?
  • A: It is a good practice to check the cable numbering during regular maintenance intervals, which can be annually or semi - annually depending on the operating environment. Any damaged or faded labels should be replaced immediately.
• Q: What type of cable markers are best for outdoor photovoltaic systems?
  • A: Cable markers made of materials resistant to UV radiation, moisture, and temperature variations are ideal. For example, plastic or metal markers that are specifically designed for outdoor use are suitable.