In the era of low-cost Internet access, the cost of the control system is critical. In the past ten years, the prices of modules and inverters have fallen by 90%, which has contributed greatly to the overall cost reduction of photovoltaic systems, but the cost of cables has not been reduced. In large-scale projects, cables account for 10% of the system, which is even higher than that of inverters. In fact, as long as the design and installation are proper, under the premise of ensuring the normal operation and safety of the system, some AC cables are made of aluminum alloy cables, which can reduce part of the cost.
Rare earth aluminum alloy cable uses high elongation aluminum alloy material. By adding boron and other rare earth trace element materials to pure aluminum, and processed by rolling technology and special annealing process, the cable has good flexibility. When the surface is in contact with air, a thin and strong oxide layer can be formed, which can withstand various corrosions. Even when overloaded or overheated for a long time, the stability of the connection can be guaranteed, and the cost is slightly higher than that of ordinary aluminum alloy cables by about 10%.
The application range of aluminum cables: long-distance overhead lines, underground cable trenches with a relatively large space, and places with reliable fixed bridges, aluminum cables may be considered.
Precautions for the use of aluminum cables:
The melting point of copper is 1080°C, while the melting point of aluminum and aluminum alloy is 660°C, so copper conductors are a better choice for fire-resistant cables. Now some aluminum alloy cable manufacturers claim that they can produce fire-resistant aluminum alloy cables and have passed the relevant national standard tests, but there is no difference between aluminum alloy cables and aluminum cables in this respect. No matter what kind of heat insulation measures the cable adopts, the cable will melt in a short time and lose its conductive function. Therefore, aluminum alloy is not suitable for fire-resistant cable conductors, nor is it suitable for use in densely populated urban distribution networks, buildings, factories and mines.
Compared with the aluminum core cable, the copper core is flexible, the allowable bend radius is small, and it is not easy to break after repeated bending. Therefore, the aluminum cable is not suitable for the occasions with many turns, more pipes, or complicated lines.
Since the terminals of the electrical switch equipment are all made of copper, the copper and aluminum are directly connected, and the chemical reaction of the galvanic battery will occur after power on: the more active aluminum will accelerate the oxidation, resulting in higher resistance at the joints and current carrying capacity. Therefore, some measures need to be taken when the copper and aluminum are connected, such as the use of copper-aluminum transition terminals or copper-aluminum transition terminals to eliminate electrochemical reactions.