Experiments performed by scientists like Benjamin Franklin and Alessandro Volta in the 17th and 18th centuries laid the foundation for understanding electrical conduction.
Samuel Morse invented the telegraph in the 1830s and 1840s revolutionizing communication in which the copper wires for telegraphy enabled long-distance communication for the first time.
The first successful transatlantic telegraph cable was laid in 1866, connecting Europe and America and significantly improving international communication. Thomas Edison and Nikola Tesla’s innovations in the late 19th century led to the development of the electric power system. Both the AC and DC systems required robust cabling for power transmission.
In 1876, Alexander Graham Bell invented the telephone, which initiated the development of an extensive telephone network, requiring significant cabling infrastructure. The widespread adaptation of electricity in homes and industries in the early 20th century demanded the development of safe and efficient electrical wiring systems.
In the Mid-20th century, there were significant developments in the Fiber optics cable that revolutionized data transmission with high-speed, high-capacity communication. The introduction of plastic insulation improved electrical cables’ durability and safety, reducing the risk of short circuits and fires.
In the Late 20th century, the advancement of computers and the internet, Ethernet cables and other networking solutions helped grow digital communication. The large network of submarine Fiber optic cables enabled global internet connectivity, making high-speed international data transfer easy and possible. The modernization of power grids included the development of high-voltage transmission lines and improved insulation technologies.
In the 21st century, modern innovations like integrating renewable energy sources like solar and wind power into the grid required advancement in power cables to handle varying loads and conditions. The rise of the smart grid and IoT demands advanced cabling solutions to connect the network of devices and sensors.
Types of Cables and Wires
Cables are majorly divided into three types according to their use cases:
- Electrical Cables
- Communication Cables
- Special Cables
Electrical Cable
An electrical cable is an assembly consisting of one or more wires running side by side or bundled with their insulation, individual coverings, and protective covering, which is used as an electrical conductor to carry electrical current efficiently and safely. Electrical cables connect a source to a device or connect two or more devices, enabling the transfer of electrical power and signal from one device to another.
The electrical cable is again divided into three types:
- Power Cables
- Control Cables
- Instrumentation Cables
Power Cable: It is an electrical assembly consisting of one or more insulated conductors. These conductors are generally bundled together and enclosed within a protective sheath used for transmitting and distributing electrical power. Electrical power can be transmitted through overhead cables or underground cables and they are designed according to their specific requirements. They are designed according to different voltage ratings, current ratings, and maximum operating temperatures according to the specific requirements.
There are different types of power cables present according to their requirements:
- Low voltage Cables: These cables are used for different household wiring applications or residential and commercial building wiring applications. These are designed for suitable applications up to several thousand volts.
- Examples: Non-Metallic (NM) Cables, Thermoplastic High Heat-Resistance Nylon-Coated (THHN) Cables
- Medium voltage Cables: These cables are used for distributing electricity in industries and between substations. These are designed for suitable applications up to several 1,000 volts to 35,000 volts.
- Examples: MV Cables, XLPE Cables
- High voltage Cables: These cables are used for long-distance power transmission to connect powering stations to cities. These are designed for suitable applications above 35,000 volts.
- Examples: HV Cables, EHV Cables
- Flexible Cables: These cables are often used for portable devices, mobile tools, and such machinery.
- Examples: Charging Cables
- Control cable: It is designed to transmit and receive the control signals and is used for automation processes, and interconnection of different electrical circuits. These cables are used in industries where precise control over the machines and its processes is required. Generally, they are made up of stranded copper due to its flexibility, durability, and great conducting capacity. They may have a shielding to prevent electromagnetic interference and ensure signal integrity.
Different types of control cables are Shielded Control Cables, Flexible Control Cables, PVC control Cables, Rubber Control Cables.
- Instrumentation cable: It is designed to transmit and receive low-energy and precise electrical signals that are used for monitoring and controlling different electrical systems and processes. These cables are required for accurate data transmission from sensors and instruments to different control units and data acquisition systems. These cables generally have multiple pairs of conductors, every pair is twisted with each other to reduce or minimize the electromagnetic interference. Shielding is a significant feature of these, cables it provides a high level of protection against EMI and RFI. These cables are generally designed for low-voltage-level applications.
Different types of instrumentation cables are Paired Instrumentation Cables, Multiple-pair Instrumentation Cables, Triad Instrumentation Cables, Coaxial Instrumentation Cables, Armoured Instrumentation Cables.
Communication Cable
These cables are designed to transmit data, voice, and video signals between different devices and systems. These are essential for various applications like telecommunications, networking, broadcasting, and data centers. Communication cables are important in ensuring reliable and efficient data transfer across various applications from simple household networks to complex industrial telecommunication networks.
There are different types of communication cables:
- Coaxial Cables
- Fiber Optics Cables
- Ethernet Cables
- Coaxial Cables: These have concentric layers of electrical conductors and insulating material. This construction ensures signals are enclosed within the cable and prevents electrical noise from interfering with the signal. The centre conductor layer is a thin conducting wire, either solid or braided copper. Coaxial cables are familiar to many of us because they connect TVs to cables or set-up boxes.
Different types of coaxial cables are Hard-line coaxial cables, Triaxial Cable, Rigid-line coaxial cables, Radiating cable.
Different types of coaxial type connectors include Bayonet Neill-Concelman (BNC), Threaded Neill-Concelman (TNC), Subminiature Version A (SMA), Subminiature Version B (SMB), QMA, Radio Corporation of America (RCA), F connectors.
- Fiber Optics Cables: These are modern cables that transmit data or information as a light pulse along a glass or plastic strand Fiber. Fiber optics cables are used for long-distance and high-performance data networking. They are critical components in modern telecommunications, the internet, and computer networking as they are capable of transmitting data over longer distances and at higher bandwidths.
Different types of Fiber Optics Cables based on the number of modes are Single-mode Fiber and Multi-mode Fiber.
Different types of Fiber Optics Cables based on the refractive index are Step-index Optical Fiber and Grade index Optical Fiber.
Different types of Fiber optics Cables based on the material used are Plastic Optical Fiber and Glass Fiber.
- Ethernet Cables: These allow the user to connect their devices such as computers, phones, routers, etc., to a LAN Local Area Network that will allow users to have internet access, and able to communicate with each other through a wired connection.
Special Cables
These cables are designed according to their unique use cases and their environments where normal standard cables can’t adequately serve. These cables have specific properties to handle extreme conditions, specialized tasks, or specific requirements.
Different types of special cables are:
- Solar Cables
- Fire Resistance Cables
- Marine Cables
- Solar Cables: Solar cables are an essential component in photovoltaic (PV) systems, connecting solar panels to inverters and other electrical components. These connections ensure that electrical power generated by solar panels is efficiently and safely transferred to the grid or storage systems. Solar cables are exposed to sunlight for lengthy periods, so they must be UV-resistant to avoid damage. These cables are designed to survive a variety of weather conditions, including high heat, cold, wetness, and mechanical stress.
- Fire Resistance Cables: Fire resistance cables, also known as fire-rated or fire-survival cables, are designed to keep the circuit intact and operational during and after fire exposure. These cables are vital for assuring the operation of critical systems in an emergency, such as fire alarms, emergency lighting, and evacuation systems.
- Marine Cables: Marine cables are specifically intended to withstand the harsh conditions of marine settings, offering power, control, and communication capabilities for a variety of nautical applications. These cables are critical to the proper operation of ships, offshore platforms, and other marine equipment. Marine cables are designed to withstand water entry, ensuring long-term functioning in damp situations. They are built of materials that are resistant to corrosion from saltwater and other marine factors.
Key Materials in Cable Construction
Conductors, Insulators, and Jackets are the three parts of a cable.
- Conductors: Those substances through which electricity can flow are called conductors.
Copper and aluminium are the most common metals used in electrical cables as electrical conductors as they have excellent conductivity and low resistance. Both these metals have high ductility and resistivity to corrosion – thus they are used for making electrical conductors. Copper is the most conductive of these two metals, also it is more conductive than all the commonly found pure metals except silver that is considerably more expensive and not as strong as copper.
Copper is considered the standard for electrical conductivity- The International Annealed Copper Standard (IACS) with a copper resistivity of 1.724µΩcm at 20°C is assigned the 100% value. The addition of impurities or work hardening of copper through drawing down will reduce its conductivity. Copper alloys are made to improve the hardness of the copper where ductility is not needed or to increase the temperature resistance, tensile strength, or flexibility which results in a decrease in conductivity. Whereas aluminium is widely available and a less expensive alternative to copper for conductors.
An aluminium conductor is only 61% as conductive as a copper conductor of the same size. Because of the difference in conductivity a much larger aluminium conductor is required to match the conductivity of an equivalent copper wire. Using a larger size conductor requires a large number of insulating materials to adequately cover the conductor and as the cross-sectional area is increased the cable may not be used in some applications. But it is lighter than copper in weight which makes it much easier to handle. As a result, aluminium is preferred in large-size cables like overhead power distribution cables.
To be continued…
Diptiman Mohanta is a Student at the Dept. of Electrical Engineering of Parala Maharaja Engineering College in Berhampur, Odisha, India.
Dr. Sarat Kumar Sahoo is a Professor at the Dept. of Electrical Engineering of Parala Maharaja Engineering College in Berhampur, Odisha, India.
