Introduction to common cables and materials used in photovoltaic power stations

Introduction: In the process of the construction of photovoltaic power station, in addition to the main equipment, such as photovoltaic modules, inverters, booster transformers, supporting the connection of photovoltaic cable materials for the overall profitability of the photovoltaic power station, the safety of operation, whether efficient, also plays a crucial role.

In recent years, the application of solar energy (PV) power generation has been increasingly extensive and developed rapidly. In the process of photovoltaic power plant construction, in addition to the main equipment, such as photovoltaic modules, inverters and booster transformers, the supporting and connecting photovoltaic cable materials also play a crucial role in the overall profitability, operation safety and efficiency of the photovoltaic power station. The following is a detailed introduction to the common uses of cable solar and materials in photovoltaic power stations and the use of the environment.

According to the system of photovoltaic power station, cables can be divided into DC cables and AC cables, which are classified as follows according to the purpose and use environment:

1. Dc cable

(1) Series cables between components.

(2) Parallel cables between the groups and between the groups and the DC distribution box (confluence box).

(3) Cable between DC distribution box and inverter.

The above cables are DC cables, which are laid outdoors more, and need to be moisture-proof, sun-proof, cold-resistant, heat-resistant, and UV resistant. In some special environments, acid, alkali and other chemical substances should be prevented.

2. Ac cable

(1) Connection cable between inverter and booster transformer.

(2) Connecting cable between booster transformer and distribution device.

(3) Connecting cables between the distribution device and the power grid or users.

This part of the cable is AC load cable, the indoor environment is laid further, can be selected according to the general power cable selection requirements.

3. Photovoltaic special cable

A large number of DC cables in photovoltaic power stations need to be laid outdoors, and the environmental conditions are harsh. The cable materials should be determined according to the resistance to ultraviolet radiation, ozone, drastic temperature changes and chemical erosion. ​Long-term use of ordinary cables in this kind of environment will cause the cable sheath to be fragile and even decompose the cable insulation layer. These conditions will directly damage the cable system, but also increase the risk of cable short circuit. In the medium and long-term, the possibility of fire or personnel injury is higher, considerably affecting the service life of the system.

Therefore, it is extremely necessary to use special photovoltaic cables and components in photovoltaic power stations. With the continuous development of the photovoltaic industry, the photovoltaic supporting parts market has gradually formed. As far as cables are concerned, a variety of specifications of professional photovoltaic cable products have been developed. The recently developed electron beam cross link cable, rated at 120℃, can withstand severe weather and mechanical shock. For another example, RADOX cable is a special solar energy cable developed according to the international standard IEC216. In an outdoor environment, the service life is 8 times that of rubber cable and 32 times that of PVC cable. Special photovoltaic cables and components not only have the best weather resistance, UV resistance and ozone erosion resistance, but also can withstand a wider range of temperature changes (for example: from -40 to 125℃). In Europe, technicians have tested the temperature of the roof to be measured as high as 100 to 110℃.

4. Cable conductor material

In most cases, the DC cables used by photovoltaic power stations work outdoors for a prolonged time. Due to the restrictions of construction conditions, the cable connections are mostly connected by connectors. Cable conductor materials can be divided into copper core and aluminum core. Copper core cable has better oxidation resistance than aluminum, lengthy life, excellent stability, modest voltage drop and modest power loss characteristics; ​in the construction, because the copper core is flexible and the allowed bending radius is tiny, it is convenient to turn and easy to pass the pipe; ​and the copper core anti-fatigue, repeated bending is not easy to break, thus the wiring is convenient; ​at the same time, the mechanical strength of the copper core is strong, and it can withstand the large mechanical tension, which brings great convenience to the construction and laying, and also creates conditions for the mechanized construction. On the contrary, due to the chemical characteristics of aluminum, the installation joint is prone to oxidation (electrochemical reaction), especially the creep phenomenon, which is easy to lead to the occurrence of failure.

Therefore, copper cable has outstanding advantages in the use of photovoltaic power stations, especially in the field of directly buried cable power supply. It can reduce the accident rate, improve the reliability of power supply, and facilitate the construction, operation and maintenance. This is the reason why copper cable is mainly used in underground cable power supply in China.

5. Cable insulation sheath material

During the installation and operation and maintenance of the photovoltaic power station, the cable may be in the soil below the ground, in the overgrowth of weeds, in the sharp edge of the roof structure wiring, exposed in the air, and the cable may bear the impact of various external forces. If the strength of the cable sheath is not strong enough, the insulation layer of the cable will be damaged, which will affect the service life of the entire cable, or lead to short circuit, fire and human injury risks. Cable research and technical personnel found that the radiation cross-linked material, compared with the radiation treatment before the mechanical strength is higher. The cross-linking process changes the chemical structure of the polymer of the cable insulating sheathing material, the fusible thermoplastic material is transformed into non-fusible elastomer material, and the cross-linking radiation significantly improves the thermal, mechanical and chemical properties of the cable insulating material.

Dc circuit in operation is frequently affected by a variety of adverse factors, resulting in ground, so that the system can not run properly. Grounding can be caused by extrusion, poor cable manufacturing, unqualified insulation materials, low insulation performance, aging of DC system insulation, or certain damage defects. In addition, the intrusion or bite of tiny animals in an outdoor environment can also cause DC grounding fault. Therefore, armored cables with a rose-proof sheath are usually used in this case.

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