Solar photovoltaic technology will be one of the green energy technologies of the future. Solar energy or photovoltaic (PV) is increasingly widely used in China. In addition to the rapid development of photovoltaic power plants supported by the government, private investors are also actively building plants to produce solar modules for global sale. But for now, many countries are still learning. There is no doubt that in order to make the best profits, companies in the industry need to learn from countries and companies that have years of experience in solar applications.
Building cost-effective and profitable photovoltaic power plants represents the most important goal and core competency of all solar manufacturers. In fact, profitability depends not only on the efficiency or high performance of the solar module itself, but also on a set of components that are not directly related to the module on the surface. However, all these components (such as photovoltaic cables, solar connectors, photovoltaic junction boxes) should be selected according to the long-term investment objectives of the tenderee. The high quality of the selected components can avoid the high repair and maintenance costs that make the solar system unprofitable.
For example, the wiring system that connects PV modules to inverters is not usually considered a critical component.
However, failure to use dedicated solar cables will affect the life of the entire system.
In fact, solar systems are often used in harsh environmental conditions, such as high temperatures and ultraviolet radiation. In Europe, sunny days will result in on-site solar system temperatures of up to 100°C. At present, the various materials available are 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, which obviously has a significant impact on the life of the system.
Environmental stress
For PV applications, the materials used outdoors should be based on UV light, ozone, severe temperature changes and chemical erosion. The use of low-grade materials under such environmental stresses will cause the cable sheath to be fragile and even break down the cable insulation layer. All of these conditions can directly increase cable system losses, as well as the risk of cable short circuits and, in the medium to long term, the likelihood of fire or human injury.
A solar cable is an electron-beam cross-link cable with a rated temperature of 120°C, which can withstand harsh climatic environments and mechanical shocks in the equipment to which it belongs. According to international standard IEC216, RADOX® solar cables has a life span of 8 times that of rubber cable and 32 times that of PVC cable in outdoor environment. These cables and components not only provide optimal resistance to weather, UV, and ozone, but can also withstand a wide range of temperature variations (e.g., from -- 40°C to 125°C).
Manufacturers tend to use double insulated rubber-sheathed cables to deal with potential hazards caused by high temperatures. However, the standard version of this type of cable is only allowed for use at a maximum operating temperature of 60°C. In Europe, temperatures measured on rooftops can be as high as 100°C.
Solar cable is rated for 120°C(20,000 hours of service). This rating corresponds to 18 years of service at a continuous temperature of 90°C; and when the temperature is lower than 90°C, its service life is longer. Typically, solar equipment is required to last more than 20 to 30 years.
For all these reasons, it is very necessary to use special solar cables and components in solar energy systems.
Resistance to mechanical load
In fact, during installation and maintenance, cables may be routed along the sharp edges of the roof structure, while cables are subject to pressure, bending, tension, cross-stretching loads and strong shocks. If the cable sheath is not strong enough, the insulation layer of the cable will be seriously damaged, which will affect the service life of the cable, or lead to problems such as short circuit, fire and human injury.
Materials that have been cross-linked by radiation have high mechanical strength. The cross-linking process changes the chemical structure of the polymer, the fusible thermoplastic material is converted to the non-fusible elastomer material, and the cross-linking radiation significantly improves the thermal, mechanical and chemical properties of the cable insulation material.
electrical
1. Dc resistance The DC resistance of the conductor core of the finished cable is not greater than 5.09ω /km at 20℃.
2. The finished cable (20m) will not break down after being immersed in water at (20±5)℃ for 1h through 5min voltage test (6.5kV AC or 15kV DC).
3. The length of the long-term DC voltage resistant sample was 5m, and the sample was put into distilled water containing 3% sodium chloride (NaCl) at (85±2)℃ for (240±2)h, and the two ends were 30cm above the water surface. 0.9kV DC voltage is added between the wire core and water (the conductive wire core is connected to the positive pole, and the water is connected to the negative pole). After taking out the sample, the immersion voltage test is carried out. The test voltage is 1kV AC, and no breakdown is required.
4. Insulation resistance The insulation resistance of the finished cable shall be no less than 1014 ω •cm at 20℃, and no less than 1011 ω •cm at 90℃.
5. Jacket surface resistance The jacket surface resistance of the finished cable should be no less than 109ω.
Application scope of photovoltaic cables
Widely used in indoor and outdoor solar equipment electrical installation lines.
Characteristics: Low smoke halogen free, excellent cold resistance, ultraviolet resistance, ozone resistance and climate resistance. Flame retardant, cut mark resistance, penetration resistance. Cable protection level ⅱ.
Ambient temperature: -40℃ ~ +90℃;
conductor maximum temperature: 120℃(allow short circuit temperature 200℃ within 5s);
rated voltage: AC0.6/1kV DC1.8kV
Design life: 25 years