Technical Difficulties in Submarine Cable
Submarine cables are cables laid at the bottom of rivers, lakes and sea. They have a history of more than one hundred years. They were originally used for power supply to offshore lighthouses and other equipment. Now submarine cables are mainly used for connecting islands to the mainland or islands, Offshore wind farms, grid connections between offshore rigs, communications links, short-range rivers and more. Its function has changed from the simple power cable, communication cable to the transmit of power and communication optoelectronic composite cable.
Submarine cables have the main types of insulation cross-linked polyethylene insulated cables, polyethylene insulated cables, EPR insulated submarine cables. XLPE insulated submarine cable has the following advantages: XLPE cable is solid insulation, low operating costs; XLPE Submarine cable without lead sheath, bending radius, light weight, can be produced, laid longer, and in laying installation and transportation than the charge Oil and Cable Simple PE and EPR Insulation: Cables EPR cables have a large dielectric constant compared to XLPE cables, but they are much better than polyethylene cables in protecting against twigs and Partial discharge, generally only for medium voltage submarine cable.
Submarine cable’s demand is increasing, which provides a broad market prospects of the cable manufacturing industry . but the ocean condition is complex, the technical difficulties are
1.Waterproof points of submarine cable
When the mechanical stress or external are damage that caused by cable sheathing and insulation, joint damage, moisture or moisture along the cable longitudinal and radial gap immersion, they will reduce the electrical insulation strength, so most high-pressure submarine cables have to prevent moisture invasion of the longitudinal, Radial waterproofing measures. Radial measures are mainly in the insulation shield and metal shielding around the outer semi-conductive water blocking tape expansion, the metal shield to add a metal waterproof layer that is metal sheath, medium voltage cable electric field strength is relatively low, the general use of aluminum-plastic composite Jacket, high-voltage cable is used lead, aluminum, stainless steel metal gland. Polymer jacket waterproof, but there is a certain degree of water absorption, the jacket to add a water-blocking agent to absorb water.
2. Metal sheath and armored anti-corrosion, anti-corrosion design
Submarine cable life to some extent depends on the corrosion resistance of steel wire armor life, it requires the use of a special wire --- zinc-aluminum-magnesium alloy coated steel wire armor. The outer jacket made of medium and high density polyethylene can overcome the shortcoming of asphalt being easy to wear and falling off, and can form better protection for the steel wire armor. Steel wire armor plus polypropylene rope outer layer, can improve the cable resistance to sea water erosion and construction wear and tear.
3. Submarine cable monitoring and safety early warning and temperature control
Submarine geological environment is complex, earthquakes, seabed collapse, landslides, ocean currents, marine life and the breakdown of ships, are likely to cause cable rupture, damage,affecting the safe operation of the cable. Submarine cable monitoring can be used insulation resistance method and resistance fault range finder, can quickly detect the cable is damaged and the location of the point of failure.