1. There are two main types of partial corrosion of AAC conductors: chemical corrosion and electrochemical corrosion
◆Chemical corrosion: refers to the corrosion of metals in the atmosphere with oxygen, chlorine, sulfur dioxide, hydrogen sulfide and other gases.
After the metal surface interacts with oxygen, different metal oxides are formed.
Aluminum oxide can form a dense surface protective film with a certain hardness.
The iron oxide structure is loose, easy to fall off, and continue to infiltrate and diffuse into the metal, destroying the material.
Copper oxide, commonly known as patina, is between the above two and is a toxic substance.
◆Electrochemical corrosion: refers to the formation of metal corrosion process after the galvanic cell is composed of metal and medium. When two metals with different electrode potentials are connected and there is water or other electrolytes in between, there will be formation between the two metals The current forms a galvanic cell, in which one metal is at a positive potential and the other is at a negative potential. The metal at the negative potential is continuously accumulated in the ion state through the electrolyte to the metal at the positive potential. The metal at the negative potential is gradually lost and destroyed, forming electrochemical corrosion. The greater the difference between the electrode potentials of the two metals, the stronger the electrochemical corrosion. The higher the temperature, the more serious the corrosion of the metal.
Different metals have different electrode potentials. The electrode potential sequence of several commonly used metals is: metal Ag (silver) Cu (copper) Pb (lead) Sn (tin) Fe (iron) Zn (zinc) A1 (aluminum). Potential +0.8+0.334-0.122-0.16-0.44-0.76-1.33 The greater the negative value of the electrode potential, the stronger the tendency to become ions in the electrolyte, that is, the more likely it is to be corroded. The negative value of the electrode potential of aluminum is relatively large, but because its surface often has a protective layer of oxide film, it can improve its corrosion resistance.
Rare earth aluminum alloy materials add rare earth elements to aluminum, which can purify, improve purity, fill surface defects, and refine grains. It reduces segregation and eliminates the effect of microscopic unevenness that leads to local corrosion. It also brings about the negative shift of the electrode potential of aluminum, which has the anodic effect and excellent electrical conductivity, thereby greatly improving the corrosion resistance of aluminum. This material has a unique anti-corrosion mechanism for the corrosion problems of C1- and petroleum in the marine environment and S, H2S+C02 in the chemical environment. The strong reducing properties of rare earth metals can effectively combine with the strong oxidizing properties of S, H2S, and C1-, and interact to form stable compounds (C1- and rare earth aluminum alloys form stable coordination compounds), which will oxidize and reduce chemical reactions. The process is organically unified and interacts. It fundamentally cuts off the corrosion damage caused by the oxidation activities of corrosive media such as S, H2S, and C1-, thus thoroughly solving the problems that have not been well resolved in developed countries including the United States. , According to the test and engineering case data analysis of Beijing Nonferrous Metals Research Institute and other national testing departments, it is shown that in chloride ion, seawater, marine atmosphere, salt spray environment (dry and wet alternate), saturated HzS, sulfur, and high temperature and high pressure environmental conditions Below, the annual corrosion rate of rare earth aluminum alloy is zero or almost zero.
2. Insulation part
◆The current carrying capacity of a power cable refers to the maximum current allowed by the cable conductor under the maximum allowable temperature. When designing and selecting cables, the heat generated by the loss of each part of the cable should not exceed the maximum allowable temperature of the cable. In most cases, the transmission capacity of the cable is determined by the maximum temperature of the cable. The maximum allowable temperature of the cable depends mainly on the maximum temperature of the cable. Due to the thermal aging performance of the insulating materials used, because the operating temperature of the cable is too high, the aging of the insulating material will accelerate and the cable life will be greatly shortened. If the cable runs above the maximum allowable temperature, the cable will work safely for 30 years.
◆XLPE is the abbreviation of the English name of cross-linked polyethylene. Polyethylene is a linear molecular structure, which is easily deformed under high temperature. The process of cross-linking polyethylene turns it into a network structure. This structure has strong resistance to deformation even at high temperatures.
◆The excellent anti-aging properties and super heat-resistant deformation of cross-linked polyethylene determine that high current can be allowed to pass under the conditions of normal operating temperature (90C), short-term failure (130C) and short circuit (250C). Because its operating temperature is 20C higher than that of polyvinyl chloride, it has excellent thermal resistance, increases the anti-aging performance of the insulation, and greatly increases the lifespan.