The successful operation of offshore wind power projects is inseparable from reliable submarine cable systems. As a key transmission channel between offshore wind farms and land, submarine cables undertake the important tasks of transmitting power and transmitting communication signals. In the production process of submarine cables, the quality of each link needs to be strictly controlled to ensure the reliability and stability of the submarine cable. This article mainly introduces the basic structure and commonly used materials of submarine cables, as well as the key factors affecting quality that need to be paid attention to during the production process of submarine cables.
Submarine cables play the role of both "blood vessels" and "nerves" in the entire wind farm operating structure. In addition to collecting and transmitting electrical energy, the optical cables inside them are also the channels for wind farm communication signals. Due to long-term operation in complex submarine environments, submarine cables have higher requirements than land cables in terms of anti-interference and corrosion resistance. They need water-blocking conductors and buffering water-blocking layers to meet the water-blocking performance. Asphalt is needed for anti-corrosion and waterproofing. The overall technical and performance requirements are higher.
Common submarine cables include extruded-insulated cross-linked polyethylene (XLPE) submarine cables, wrapped-insulated oil-filled submarine cables, and sticky impregnated paper insulated (MI) submarine cables. In recent years, extruded-insulated cross-linked polyethylene (XLPE) submarine cables are commonly used in domestic offshore wind power.
The key factors affecting the quality of submarine cables mainly include: conductor, insulation layer, and shielding layer.
(1) Conductor
Submarine cables generally use copper wire as the conductor. During the production process, we must first ensure the quality of copper wire, and secondly ensure the conductor processing technology to avoid burrs and mechanical damage. Inferior metal copper or recycled copper with more impurities will increase resistance, increase loss, reduce current carrying capacity, cause conductor overheating, and accelerate insulation aging, thus affecting the life of the cable. During the conductor production process, defects such as burrs and mechanical damage may occur due to damage to the drawing die and other external forces, which may easily lead to discharge breakdown and affect the normal use of submarine cables.
Therefore, manufacturing supervisors should strictly control the raw materials of conductors and strengthen the detection of DC resistance of conductors during the production process to avoid the occurrence of hidden risks.
(2) Insulation layer
The insulation layer of submarine cables is generally made of cross-linked polyethylene (XLPE), which is processed and formed by an extruder to reduce the risk of current leakage and electric shock. If the process control is not in place, the insulation thickness does not meet the standard, the eccentricity of the submarine cable insulation exceeds the standard, or the insulation layer contains impurities, the thickness of the submarine cable insulation will become thinner, the ability to resist discharge will decrease, and the phenomenon of breakdown of the insulation layer will easily occur, affecting The service life of the cable.
Manufacturing supervisors should strengthen the intensity and frequency of online inspections during the production process to prevent such quality hazards in advance and discover them in a timely manner.
(3) Shielding layer
The shielding layer of a submarine cable is divided into an inner shielding layer and an outer shielding layer. It is generally made of semi-conductive PE compound and processed and formed by an extruder to exert a uniform electric field on the submarine cable. If due to factors such as extrusion equipment, process control, and saving of raw materials, the shielding thickness is lower than the national standard value or the shielding is not smooth and round enough, the uniform electric field effect will be weakened. If the electric field is strong or abnormal discharge occurs, the insulation layer will easily break down. Breakdown affects the service life of submarine cables.
Manufacturing supervisors should strengthen the review of process documents, strengthen online testing and random inspections, and urge manufacturers to do a good job in equipment maintenance before production.
During the production process of submarine cables, key quality factors such as conductors, insulation layers and shielding layers require special attention. During the manufacturing supervision process, staff must strengthen the quality control of raw materials, as well as strict control of production processes and finished products, to ensure that each submarine cable is of high quality and reliable, and to ensure the stable operation of offshore wind farms.