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The Hazards of Moisture to Power Cable

April 16, 2022

The rapid development of electric power industry has promoted the development of the electrical industry supporting the electric power industry, especially the wire and cable industry. The variety development of wire and cable shows a diversified trend. Wires and cables have developed from simple power transmission to multi-function, that is, some new characteristics have been added according to different uses, such as the water resistance requirements of power cables. With the deepening of the research and understanding of insulation water absorption and water tree, people are more and more aware of the importance of waterproof performance for medium and high voltage power cables. In areas with high groundwater level or perennial rainfall. More and more users require waterproof performance for cables.

After water is immersed in the cable, the main influence is on the conductor and insulation of the cable. As far as the conductor is concerned, the cable is in a thermal stable state during normal operation, and the conductor temperature is generally above 60. If there is water immersion, it will lead to conductor oxidation and increase the energy loss resistance between conductor single wires, which increases the conductor resistance and the energy loss of transmission line,
In terms of insulation, although polyethylene is a non-polar hydrophobic material that is very difficult to dissolve in water, polyethylene is a semi crystalline polymer composed of crystalline phase and amorphous phase. The phase structure of polyethylene is compact, but there are defects at the grain boundary; The molecular arrangement in the amorphous phase is loose. There is a large gap between molecules. Water molecules are polar. Under the combined action of diffusion force and electric field force under alternating electric field, water molecules can easily penetrate into the capacity gap of amorphous phase and grain boundary defects of crystalline phase of polyethylene. The above problems also exist in the molecular structure of cross-linked polyethylene. At the same time, there are many cross-linked by-products in cross-linked polyethylene as impurities, so cross-linked polyethylene also has large water absorption under alternating electric field. Cross linked polyethylene and polyethylene insulation will produce water tree after absorbing water, which will cause breakdown and damage to the running cable.

Zhenglan Cable Technology Co., can do radinal water prevention structure by adding water prevention tape into different layer of the MV cable. If you are looking for such performance for MV cable, please come to us.