Cables are essential components in modern electrical and electronic systems, but have you ever wondered what lies beneath their protective outer layers? In this article, we will dissect the parts of a cable and explore their functions.

cable

The Conductor

The conductor is the core of any cable, serving as the pathway through which electrical current flows. The most common conductor materials include:

  • Copper: Copper is the most widely used conductor material due to its excellent electrical conductivity, second only to silver, but more abundant and cost-effective. Its inherent ductility and durability further contribute to its widespread use in power and communication cables. Bare copper is often preferred for applications involving pressure terminations. Copper conductors can be solid or stranded, with stranded conductors consisting of multiple thin wires twisted together, providing excellent flexibility and durability.
  • Aluminum: Despite its lower electrical conductivity compared to copper, aluminum is a lighter and more economical alternative, especially in transmission lines and overhead cables. While aluminum is approximately 70% lighter than copper, its conductivity is about 60% lower for the same cross-sectional area. One potential issue with using aluminum conductors is galvanic corrosion, which can occur when aluminum comes in contact with brass or copper fittings in a humid environment.
  • Steel: Steel is not as conductive as copper or aluminum but offers distinct advantages in applications that require high tensile strength, such as the construction industry and cables that demand excellent mechanical resilience. Silver, while having the highest conductivity of all metals, is often used as a coating on copper to enhance conductivity and corrosion resistance.

Insulation

The insulation wraps around the conductor, acting as a barrier to prevent current leakage from the conductor. There are two main types of insulation materials:

Thermoplastics

Thermoplastic insulation softens when heated and solidifies when cooled without undergoing permanent chemical changes. Common thermoplastic insulation materials include:

  • Polyvinyl Chloride (PVC)
  • Polyethylene (PE)
  • Polypropylene (PP)
  • Thermoplastic Elastomer (TPE)

Thermosets

Thermosets undergo chemical changes during the manufacturing process (extrusion) to form more stable compounds that can withstand higher operating temperatures. Examples of thermoset insulation materials include:

  • Cross-linked Polyethylene (XLPE)
  • Ethylene Propylene Rubber (EPR)
  • Silicone Rubber (SiR)

Shielding

The primary purpose of shielding is to protect the integrity of the transmitted signal by preventing external noise from coupling into the cable and controlling the electromagnetic energy radiated by the cable itself. This helps prevent interference with nearby sensitive electronic equipment. In some cases, the shield can also act as a Faraday cage, further isolating the internal conductor from external electromagnetic fields. Common types of shielding include:

  • Foil Shield: A thin layer of aluminum or copper foil wrapped around the insulated conductor, providing excellent high-frequency shielding.
  • Braid Shield: A woven mesh of bare or tinned copper wires, offering good low-frequency shielding and mechanical strength.
  • Spiral/Serve Shield: A spiral-wrapped bare or tinned copper wire, providing moderate shielding effectiveness and flexibility.
  • Tape Shield: A non-woven tape with a metallic backing, often used in conjunction with other shielding methods.
  • Combination Shield: A mix of different shielding types, such as foil-braid or braid-braid, to achieve optimal shielding performance.
  • Conductive Polymers: A polymer matrix filled with conductive particles, offering lightweight and flexible shielding solutions.

The Outer Jacket or Sheath

The outermost layer of the cable is the jacket, which serves as the primary line of defense for the internal components, including the insulation and conductor core. This outer covering provides critical mechanical protection against abrasion, crushing forces, and impact damage during installation, handling, and use. Additionally, the jacket offers important environmental resistance to moisture, chemicals, ultraviolet (UV) radiation, and ozone, safeguarding the internal components from degradation and corrosion.

Common jacket materials include:

  • Polyvinyl Chloride (PVC)
  • Polyethylene (PE)
  • Thermoplastic Elastomer (TPE)
  • Thermoplastic Polyurethane (TPU)
  • Polyamide (Nylon)
  • Fluoropolymers (e.g., PTFE, FEP)

Additional Components in Specialized Cables

Some specialized cables may include additional components to enhance their performance or meet specific application requirements:

  • Fillers: Non-conductive materials used to maintain the cable’s shape and provide mechanical stability.
  • Tapes: Thin layers of material wrapped around the conductor or insulation for added protection or identification.
  • Strength Members: Fiberglass, aramid, or steel elements incorporated to provide tensile strength and limit cable elongation.
  • Rip Cords: Strings or cords placed beneath the jacket to facilitate easy removal for termination or splicing.
  • Armor: Metallic or non-metallic layers applied to the cable exterior for extra mechanical protection and durability.