Main content:
1. What is a photovoltaic cable
Photovoltaic cable, that is, special cable used in PV system, is also mainly used in photovoltaic power plants. It has high temperature resistance, cold resistance, oil resistance, acid and alkali resistance, ultraviolet protection, flame retardant environmental protection, long service life and other advantages. It is mainly used in harsh climatic conditions.
Photovoltaic cable is often exposed to sunlight, and solar systems are often used in harsh environments with high temperatures and ultraviolet radiation. In Europe, sunny days will cause the on-site temperatures of solar systems to reach up to 100°C. Europe uses distributed pv system to achieve maximum value. Currently, we can use a variety of materials, including PVC, rubber, TPE and high-quality cross-link materials.
But unfortunately, rubber cables rated at 90°C, and even PVC cables rated at 70°C, are often used outdoors. Although there are many contractors who do not choose special cables for solar systems in order to save costs but instead choose ordinary PVC cables instead of photovoltaic cables, this will obviously greatly affect the service life of the system.
The characteristics of photovoltaic cable is determined by their special insulation and sheath materials. We call this cross-linked polyethylene. After accelerator irradiation, the molecular structure of the cable material changes, providing various aspects of performance.
2. The difference between photovoltaic cable and ordinary cable
● Photovoltaic cable
Conductor: copper conductor or tinned copper conductor.
Insulation: irradiated cross-linked polyolefin insulation
Sheath: irradiated cross-linked polyolefin insulation
● Normal cable
Conductor: copper conductor or tinned copper conductor
Insulation: PVC or XLPE insulation
Sheath: PVC sheath
It can be seen that the conductor of ordinary cable and photovoltaic cable is the same, but the insulation and sheath are not the same, and ordinary cable is only suitable for laying and use in ordinary environments, while photovoltaic cable is mainly used in harsh climatic conditions, with high temperature resistance, cold resistance, oil resistance, acid and alkali resistance, ultraviolet protection, flame retardant environmental protection, long service life and other advantages.
In fact, during installation and maintenance, the cable is subjected to pressure, bending, tension, cross-tensile loads and strong impacts. If the cable sheath is not strong enough, cable insulation will be severely damaged, affecting the service life of the entire cable, or leading to problems such as short circuits, fire and personal injury hazards.
3. Types of photovoltaic cable
In the entire photovoltaic system, although the cost of the cable is not high, as the "blood vessel" of the photovoltaic system, it plays an important role in connecting components, inverters, distribution boxes and power grids, and has an important impact on the operational safety of the entire system, whether it is stable and efficient.
And even the overall profitability of the power station. Photovoltaic cables mainly play a connecting role in connecting the power generation area and the energy storage area, where the energy storage part is converted into electric energy and stored in the solar cells. The off grid solar batteries mainly focus on the household part in the future.
Therefore, cable selection in the photovoltaic system design process is also very critical. From the perspective of different functions, the cables in the photovoltaic system can be mainly divided into DC cables and AC cables.
① DC cable
- Cable in series between components.
- Parallel cables between strings and from strings to DC distribution boxes (combiner boxes).
- Cable between the DC distribution box and the inverter.
The above cable is DC cables, outdoor laying requires more moisture, sun exposure, cold, heat, and ultraviolet resistance. Some special environments also need to prevent acid, alkali and other chemicals.
② AC cable
- Connection cable from inverter to step-up transformer.
- Connection cable from step-up transformer to power distribution unit.
- Connection cables from power distribution units to the grid or users.
This part of the cable is an AC load cable with a more indoor environment, which can be selected according to the general power cable selection requirements.
4. Why choose a photovoltaic cable
A large number of DC cables in photovoltaic power plants need to be laid outdoors, the environmental conditions are harsh, and the cable materials should be determined according to the resistance to ultraviolet rays, ozone, severe temperature changes and chemical erosion.
Long-term use of ordinary material cables in this environment will cause the cable sheath to be broken and even the cable insulation to be disassembled. These conditions will directly damage the cable system, but also increase the risk of cable short circuits and in the medium and long term, the possibility of fire or personal injury is also higher, greatly affecting the service life of the system.
Therefore, it is very necessary to use special photovoltaic cables and components in photovoltaic power plants. PV-specific cables and components not only offer optimum weather, UV and ozone resistance, but also withstand a wider range of temperature changes.
5. The principle of cables design selection
The withstand voltage value of the cable is greater than the maximum voltage of the system. For example, for a 380V output AC cable, choose a 450 or 750V cable. For the connection between the PV square matrix and the square matrix, the rated current of the selected cable is 1.56 times the maximum continuous current in the calculated cable.
For the connection of AC loads, the selected cable rated current is 1.25 times the maximum continuous current on the calculated cable. For inverter connections, the rated current of the selected cable is 1.25 times the maximum continuous current in the calculated cable.
Consider the effect of temperature on the performance of the cable. The higher the temperature, the less ampacity of the cable, and the cable should be installed in a ventilated and dissipated place as much as possible. Consider that the voltage drop should not exceed 2%. DC circuits are often affected by a variety of unfavorable factors during operation and cause grounding, making the system unable to operate normally.
Such as extrusion, poor cable manufacturing, unqualified insulation materials, low insulation performance, aging insulation of DC system, or some damage defects, can cause ground faults or become a hidden ground hazard. In addition, the invasion or bite of small animals in outdoor environments can also cause DC ground faults. Therefore, in this case, armoured cables with a functional sheath against rats are generally used.
6. How photovoltaic cable operate at high temperatures
When sunlight hits a solar panel, the panel converts solar energy into direct current energy, which needs to be processed by a series of electrical equipment before it can be connected to the grid.
Photovoltaic cable is cables used to connect these electrical equipment, which usually need to operate in outdoor, high-temperature, humid environments. In order to meet these special requirements, photovoltaic cables need to have the following characteristics:
● Weather resistance
PV cables need to be able to withstand long-term exposure to ultraviolet rays and high temperatures, and are not easy to age and deteriorate.
● Durability
Since photovoltaic cables need to be used in outdoor environments for a long time, they need to have high durability and be able to operate stably for a long time without failure.
● Rated voltage
The voltage of the solar power generation system is high, and the cable needs to have a higher rated voltage to withstand it to ensure the safe and stable operation of the system.
● Insulation performance
Photovoltaic cables need to have good insulation performance, which can prevent faults and accidents caused by electrical breakdowns and other problems of the cable.
● Quality control
In order to ensure the safe and reliable operation of photovoltaic power generation systems, photovoltaic cables need to meet a series of international and industry standards, and quality control is required.
Photovoltaic cable is commonly used in commercial, industrial and home energy storage, as well as in large-scale solar power plants, and are an essential part of solar power generation systems. Their applications cover the connection and transmission process of the entire photovoltaic power generation system.
It should be noted that different photovoltaic cables have different rated voltages and rated temperature ranges, and choosing the right photovoltaic cable is the key to ensuring the safe and stable operation of photovoltaic power generation systems.
7. Conclusion
Photovoltaic cable is a kind of cable specially used in solar power generation systems and is one of the important electrical components used to connect solar panels, inverters, power grids and other equipment. Photovoltaic cable is generally composed of conductors, insulation materials, sheath materials, etc. made of copper or aluminum.
According to different requirements, photovoltaic cable can be divided into DC photovoltaic cable and AC photovoltaic cable, DC photovoltaic cable is mainly used for connection between solar panels and inverters, and AC photovoltaic cable is mainly used for connection between inverters and power grids.
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