Introduction to Marine Cables

Marine cables are wires and cables used for power, lighting, and control of various ships and offshore oil platforms in rivers and seas. Marine cables are different from ordinary cables because they require higher technical and material requirements than ordinary cables when used in special working conditions.

Marine cables, including marine power cables, marine control cables, marine communication cables, etc. Usually, the laying space of marine cables is limited, so the armor structure adopts metal wire weaving method, which is the biggest difference between the structure and ordinary power, control, and communication cables used on land.

Similar to the main classification of wire and cable, marine cables can be divided into marine power cables (including low-voltage power cables with rated voltage and power frequency AC 1kV and below, and medium voltage power cables with rated voltage and power frequency AC 3-15kV), marine control cables, marine communication cables, marine signal cables, and marine radio frequency cables according to their scope of use.

As a commonly used series of standards for marine cables, the IEC 60092-3 standard mainly includes IEC 60092-350 "Electrical Installations in Ships - Part 350: Power, Control, and Instrumentation Cables for Ships and Offshore Installations, General Structures and Test Methods", IEC 60092-360 "Electrical Installations in Ships - Part 360: Insulation and Sheathing Materials for Power, Control, Instrumentation, and Communication Cables for Ships and Offshore Installations" IEC 60092-353 "Electrical installations in ships - Part 353: Power cables with rated voltages of 1kV and 3kV", IEC 60092-354 "Electrical installations in ships - Part 354: Single core and multi-core extruded solid insulated power cables with rated voltages of 6kV (Um=7.2kV) to 30kV (Um=36kV)", and IEC 60092-376 "Marine electrical and pneumatic installations - Part 376: Control and instrument loop 150/250V (300V) cables".

characteristic

Marine cables are safe and reliable, have a long lifespan, small size, light weight, and have excellent requirements for temperature resistance, fire resistance, flame retardancy, oil resistance, moisture resistance, seawater resistance, and excellent electrical and mechanical properties.

Classification and Function

1. According to the attributes of the ship, it can be divided into: civilian cables and military cables

① The variety and specifications of civil cables are more diverse.

② Military cables require higher safety and reliability. Compared to civilian cables, military cables are related to national defense security and are protected by law. They are more focused on safety in use, convenient operation and maintenance than functional richness, and therefore have a more singular variety and specification.

2. According to general purposes, it can be divided into: power cables, control cables, and communication cables

① Marine power cables are used for power transmission in various ships and offshore oil platforms on rivers and seas, as well as in water buildings.

② Marine control cables are used for the transmission of control signals for various ships in rivers and seas, as well as for water buildings such as offshore oil platforms.

③ Marine communication cables are used for signal transmission in various communication, electronic computers, and information processing equipment.

3. According to insulation materials, it can be divided into rubber insulated cable, polyvinyl chloride insulated cable, and cross-linked polyethylene insulated cable

① Rubber has excellent elasticity, tensile strength, elongation, wear resistance, tear resistance, and compression permanent deformation properties. It has good electrical insulation, but poor oil resistance, weather resistance, ozone resistance, and low resistance to acid and alkali corrosion; Low heat resistance, not suitable for work above 100 ℃.

② Polyvinyl chloride is the most widely used, but it contains halogens. When wires and cables are burned in accidents, toxic gases are released, seriously polluting the environment and affecting rescue efforts.

③ Crosslinked polyethylene is the best alternative material for polyvinyl chloride, known as the "green" insulation material. It does not produce harmful substances during combustion, flame retardants do not contain halogens, and toxic gases are not emitted during daily operation.

It s functions are as follows: marine power cables: used for power, lighting, and general control of various ships and offshore oil platforms in rivers and seas; Marine control cable: used for general control of various ships in rivers and seas, as well as offshore oil platforms and other water buildings; Marine communication cable: A signal transmission and control system used in various communication, electronic computers, and information processing equipment.

Selection principle

Steps and principles for selecting cables in ship power systems

1. Choose the appropriate cable model based on the purpose, laying location, and working conditions of the cable.

2. Choose an appropriate cable cross-section based on the working system of the electrical equipment, type of power supply, cable core, and load current.

3. Based on the calculation results of the system short-circuit current, whether the short-circuit capacity of the fragmented cable meets the requirements.

4. Correct the rated current carrying capacity of the cable based on the ambient temperature, and then determine whether the allowable current of the cable is greater than the load current.

5. According to the bundle laying correction coefficient, the rated current carrying capacity of the cable is corrected, and then the allowable current of the cable is judged to be greater than the load current.

6. Check the voltage drop of the line and determine if the voltage drop is less than the specified value.

7. Determine whether the cable and protection device are coordinated based on the setting value of the protection device; If there is no coordination, determine whether it is possible to change the appropriate protective device or setting value, otherwise a suitable cable carrying surface should be selected again.