In recent years, with the rapid development of solar power applications, the construction of photovoltaic (PV) power stations has been increasing. Besides the main equipment such as PV modules, inverters, and step-up transformers, the accompanying connecting PV cable materials are crucial to the overall profitability and operational safety of the PV power station. This article will provide a detailed introduction to the common cables and materials used in PV power stations.

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1. Cable Classification

Depending on the different systems of PV power stations, cables can be divided into direct current (DC) cables and alternating current (AC) cables.

1.1 Direct Current (DC) Cables

DC cables are primarily used for the series connection between PV modules, the parallel connection between strings, and the connection from the string to the DC distribution box (combiner box). These cables are usually laid outdoors and therefore need to have moisture resistance, sun protection, cold resistance, heat resistance, and UV resistance. In certain special environments, they also need to have resistance to acid and alkali chemical corrosion.

1.2 Alternating Current (AC) Cables

AC cables are mainly used for connections from the inverter to the step-up transformer, from the step-up transformer to the distribution device, and from the distribution device to the grid or end-users. These cables are usually laid indoors and can be selected according to the general requirements for power cables.

2. Photovoltaic Cables

A large number of DC cables in PV power stations need to be laid outdoors under harsh environmental conditions. Therefore, the material of PV cables should be selected based on resistance to UV rays, ozone, severe temperature changes, and chemical corrosion. Ordinary cable materials, under these conditions, may lead to cable sheathing becoming brittle or even decompose the cable insulation layer, thereby damaging the cable system, increasing the risk of cable short circuits, and possibly causing fires or personal injuries, severely affecting the system’s lifespan.

3. Cable Conductor Materials

The DC cables used in PV power stations usually need to work outdoors for a long time and are restricted by construction conditions, with many connections made using connectors. Therefore, the choice of cable conductor material is particularly important.

3.1 Copper Core Cables

Copper core cables have good oxidation resistance, a longer lifespan, stable performance, smaller voltage drop, and power loss. In addition, copper core cables are flexible, convenient for construction, have strong fatigue resistance, high mechanical strength, and can withstand large mechanical tension, providing conditions for mechanized construction.

3.2 Aluminum Core Cables

Aluminum core cables have a lower cost but poorer oxidation resistance, prone to oxidation, and creep, leading to a higher rate of failures.

4. Cable Insulation and Sheath Materials

In the installation and maintenance of PV power stations, cables may be laid underground in soil, among weeds and rocks, on sharp edges of roof structures, or exposed to the air, subject to external impacts. If the cable sheath strength is insufficient, the cable insulation layer will be damaged, thereby affecting the cable’s lifespan, and even causing short circuits, fires, and personal injuries.

Studies have shown that cable materials treated with radiation cross-linking have higher mechanical strength. The radiation cross-linking process changes the chemical structure of the cable insulation sheath material polymers, converting fusible thermoplastic materials into non-fusible elastomer materials, and improving the thermal, mechanical, and chemical characteristics of the cable insulation materials.

5. DC Circuit Grounding Issues

DC circuits often encounter grounding issues during operation due to various adverse factors, preventing the system from operating normally. For example, squeezing, poor cable manufacturing, substandard insulation materials, low insulation performance, aging of DC system insulation, or the presence of certain damage defects can cause grounding or become a hidden grounding hazard.

Conclusion

The selection of appropriate cables and materials is vital for the reliability, safety, and efficiency of photovoltaic power stations. It is essential to consider the environmental conditions, material properties, and potential operational issues when choosing cables for PV applications to ensure the long-term stability and profitability of solar energy projects.