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Introduction of cables and materials common in photovoltaic power stations
- Jun 01, 2018 -

In recent years, the application of solar energy (PV) power generation has become increasingly widespread and has developed rapidly. In addition to major equipment, such as photovoltaic modules, inverters, and step-up transformers, PV solar power cables connected to PV power plants have been used for the overall profitability of photovoltaic power plants. The ability, safety of operation, and efficiency are also important. The following is a detailed introduction to the uses and environments of cables and materials commonly used in photovoltaic power plants.

The cables can be classified into DC cables and AC cables according to the system of the photovoltaic power station. They are classified according to their different uses and environments:

1. DC cable

(1) A series cable between components and components.

(2) Parallel cables between strings and their strings to DC distribution boxes (confluence boxes).

(3) The cable between the DC distribution box and the inverter.

The above cables are all DC cables. They are laid outdoors in large quantities and need to be protected from moisture, sunlight, cold, heat, and UV rays. In some special circumstances, they must also be protected against acids and alkalis.

2. AC cable

(1) Connecting cable from inverter to step-up transformer.

(2) Connecting cable for step-up transformer to power distribution unit.

(3) The connection cable from the power distribution unit to the grid or user.

This part of the cable is an AC load cable, and there are many indoor installations. It can be selected according to the general power cable selection requirements.

3. Photovoltaic special cable

A large number of DC cables in photovoltaic power plants need to be laid outdoors, and the environmental conditions are harsh. The cable materials should be determined according to UV resistance, ozone, severe temperature changes, and chemical erosion. The long-term use of cables with common materials in this type of environment will result in fragile cable jackets and even breakdown of cable insulation. These conditions can directly damage the cable system, and at the same time increase the risk of short-circuiting the cable. In the medium and long term, the possibility of fire or personal injury is also higher, which greatly affects the service life of the system.

Therefore, it is very necessary to use photovoltaic dedicated cables and components in photovoltaic power plants. With the continuous development of the photovoltaic industry, the market for photovoltaic accessory components has been gradually formed. In terms of cables, a variety of photovoltaic professional cable products have been developed. The recently developed electron beam cross-link cable, rated at 120°C, withstands harsh weather conditions and withstands mechanical shocks. Another example is RADOX cable is a solar energy special cable developed according to the international standard IEC216, in the outdoor environment, the service life is 8 times that of the rubber cable, 32 times that of the PVC cable. Photovoltaic-dedicated cables and components not only have the best weather resistance, UV and ozone resistance, but also withstand a wide range of temperature changes (for example, from -40 to 125°C). In Europe, technicians have tested that the temperature measured on the roof can reach 100-110°C.

4. Cable conductor material

Most of the DC cables used in photovoltaic power plants are used for long-term outdoor work. Due to the restrictions of construction conditions, the cables are often connected using connectors. Cable conductor material can be divided into copper core and aluminum core. Copper core cable has better oxidation resistance than aluminum, long service life, better stability, low pressure drop and small power loss; due to the good flexibility of the copper core in the construction, the allowable radius of curvature is small, so the turning is convenient and the pipe is worn Easy; and copper core fatigue resistance, repeated bending is not easy to break, so the wiring is convenient; at the same time the copper core of high mechanical strength, can withstand greater mechanical tension, to bring great convenience to the construction and laying, but also to create conditions for mechanized construction . On the contrary, the aluminum core cable, due to the chemical properties of the aluminum material, is prone to oxidation (electrochemical reaction) in the mounting joints, and is particularly prone to creep phenomena, which can easily lead to failures.

Therefore, copper cables have outstanding advantages in the use of photovoltaic power plants, especially in the field of direct-buried laying of cable power. It can reduce the accident rate, improve the reliability of the power supply, convenient construction and maintenance. This is the reason why the main use of copper cables in underground power supply is currently in China.

5. Cable insulation sheath material

During the installation, operation, and maintenance of photovoltaic power plants, cables may be routed in the soil below the ground, overgrown with weeds, on the sharp edges of the roof structure, and exposed to the air. The cables may be subject to various external forces. If the strength of the cable sheath is not sufficient, the cable insulation will be damaged, which will affect the service life of the entire cable or cause short circuit, fire and danger of personal injury. Cable technicians found that cross-linked materials have higher mechanical strength than radiation treatment. The cross-linking process changes the chemical structure of the cable insulation sheath material polymer, converts the meltable thermoplastic material into a non-meltable elastomer material, and cross-link radiation significantly improves the thermal, mechanical and chemical properties of the cable insulation material. characteristic.

In operation, the DC loop is often affected by various unfavorable factors and causes grounding, making the system unable to operate normally. Such as extrusion, poor cable manufacturing, insulant material failure, low insulation performance, insulation aging of the DC system, or the presence of certain damage defects can cause grounding or become a grounding hazard. In addition outdoor environment, small animals invade or bite can also cause DC ground fault. Therefore, in this case, armored, cabled with a rodent protection functional sheath is generally used.