Wires and cables are the fundamental pathways through which electrical energy is transmitted and distributed. Their proper selection and installation are paramount for system efficiency, safety, and long-term reliability.

Types of Wires:

• Wire: Generally refers to a single metallic conductor. It can be solid or stranded. When insulated, the insulation is typically thin.
• Single Core Wire (Solid Conductor):
• Construction: Composed of a single, solid strand of conducting material (e.g., copper). It is usually covered with an insulating layer.
• Characteristics: Relatively stiff and rigid, which makes it suitable for fixed wiring installations where the wire is not frequently bent or moved. It offers excellent mechanical strength.
• Application: Primarily used for internal wiring in conduits within walls, earthing conductors (due to its rigidity), and in applications where low resistance and good mechanical stability are needed for fixed connections.
• Multi Core Wire (Stranded Conductor):
• Construction: Made up of multiple thinner strands of conducting material twisted together to form a single larger conductor. This composite conductor is then insulated.
• Characteristics: Significantly more flexible than single-core wire of the same overall cross-sectional area. It is less prone to breaking when subjected to repeated bending or vibration.
• Application: Ideal for flexible cables, appliance cords, internal wiring of electronic equipment, and any application where bending or movement is anticipated (e.g., wiring in motor control panels, portable equipment).

Types of Cables:

• Cable: A complete assembly consisting of one or more insulated conductors, often twisted together, and encased within an overall protective outer sheath. Cables can also include fillers, binders, and shielding layers.
• PVC (Polyvinyl Chloride) Cables:
• Insulation Material: Polyvinyl chloride, a thermoplastic polymer widely used due to its versatility.
• Characteristics:
  • Good Electrical Insulator: Effectively prevents current leakage.
  • Flame Retardant: Self-extinguishing properties, making it safer in case of fire.
  • Chemical and Abrasion Resistance: Resists many chemicals and offers decent protection against mechanical wear.
  • Flexibility: Generally flexible and easy to handle and install.
  • Cost-Effective: Economical to produce, making it a popular choice.
  • Temperature Limitations: Can become brittle at very low temperatures and soften at higher temperatures (typically rated up to 70°C continuous operation), which limits its current carrying capacity in warmer environments.
  • Applications: Dominant for general-purpose wiring in residential buildings (lighting, socket circuits), commercial installations, and low-voltage control circuits.
• XLPE (Cross-Linked Polyethylene) Cables:
• Insulation Material: Polyethylene that has undergone a chemical cross-linking process. This converts the linear polyethylene chains into a three-dimensional network, creating a thermosetting material.
• Characteristics:
  • Superior Thermal Properties: Higher continuous operating temperature (typically up to 90°C) and much higher short-circuit temperature (up to 250°C) compared to PVC.
  • Excellent Electrical Properties: Low dielectric loss, suitable for higher voltage applications.
  • Better Mechanical Strength: More resistant to deformation under heat and pressure.
  • Good Chemical and Moisture Resistance: Superior to PVC in many harsh environments.
  • Lower Weight: Generally lighter than PVC cables for comparable ratings.
• Applications: Preferred for power distribution in industrial plants, underground and overhead power lines, high-voltage applications, and situations demanding higher current ratings, better thermal performance, and improved reliability.
• Armored Cables:
• Construction: Features an additional layer of mechanical protection, typically a spiral winding of galvanized steel wires (SWA - Steel Wire Armored) or steel tapes (STA - Steel Tape Armored), placed beneath the outer sheath.
• Function: The armor provides robust protection against external mechanical stresses such as crushing, impact, and even rodent damage. This significantly enhances the cable's durability in harsh environments. The armor can also serve as an additional protective earth conductor in some systems.
• Applications: Primarily used for direct burial in the ground (e.g., garden lighting, outdoor power feeds), industrial installations where cables are exposed to potential mechanical damage, and in areas requiring enhanced physical protection.

Conductor Materials:

• Copper:
• Properties: Possesses exceptional electrical conductivity, second only to silver. It exhibits high tensile strength, excellent ductility (can be easily drawn into fine wires), and malleability (can be shaped without breaking). It forms a relatively non-conductive and stable oxide layer, which does not significantly impede electrical connections.
• Advantages: Superior conductivity leads to lower resistive losses and smaller conductor sizes for a given current. High mechanical strength and excellent resistance to corrosion make connections reliable and durable.
• Limitations: More expensive and denser (heavier) than aluminum.
• Applications: The preferred material for most electrical wiring in buildings, appliance cords, motor windings, transformers, and electronic circuits due to its reliability and efficiency.
• Aluminum:
• Properties: Offers significantly lower density (lighter) and is more abundant (cheaper) than copper. However, its electrical conductivity is only about 60% of copper's for the same cross-sectional area. Aluminum is prone to forming a resistive oxide layer on its surface when exposed to air, which can lead to poor connections if not properly handled. It also exhibits "creep" or cold flow under sustained pressure, meaning it can slowly deform away from screw terminals, leading to loose connections and potential overheating.
• Advantages: Cost-effective for larger cross-sectional areas, significantly lighter weight (advantageous for overhead transmission lines).
• Limitations: Lower conductivity necessitates larger conductor sizes for the same current rating, susceptible to oxidation at connection points, lower mechanical strength, and issues with creep at terminals. Special connectors and installation techniques are required for aluminum wiring to mitigate these issues.
• Applications: Widely used for overhead power transmission and distribution lines (where weight is a critical factor), larger feeder cables in industrial and commercial buildings, and sometimes for service entry cables to residential properties. Less common and generally discouraged for interior branch circuit wiring in homes due to connection issues.

Wire Gauges (AWG/SWG) and Current Carrying Capacity (Ampacity):

• Wire Gauge Systems: Standardized methods to classify the cross-sectional area (and thus diameter) of electrical conductors.
• AWG (American Wire Gauge): Predominantly used in North America. Counter-intuitively, a smaller AWG number indicates a larger wire diameter and thus a greater current carrying capacity. For example, 10 AWG is thicker than 14 AWG.
• SWG (Standard Wire Gauge): Primarily used in the United Kingdom and some Commonwealth countries. In contrast to AWG, a larger SWG number indicates a larger wire diameter. For example, 10 SWG is thicker than 14 SWG.
• Current Carrying Capacity (Ampacity): This is the most crucial rating for a conductor. It defines the maximum continuous electrical current (in Amperes) that an insulated conductor or cable can safely carry under specified conditions without exceeding its maximum permissible operating temperature. Exceeding this limit causes overheating, which can degrade insulation, lead to short circuits, and pose a fire hazard.
• Factors Affecting Ampacity:
• Conductor Material: Copper generally has a higher ampacity than aluminum for the same cross-sectional area due to its superior conductivity.
• Cross-sectional Area: Larger conductor cross-sectional area means lower electrical resistance, allowing higher current to flow without excessive heating. Ampacity increases with conductor size.
• Insulation Type/Temperature Rating: Different insulation materials have different maximum operating temperatures (e.g., PVC 70°C, XLPE 90°C). A cable with higher temperature-rated insulation can carry more current for the same conductor size before its insulation integrity is compromised.
• Ambient Temperature: Higher surrounding air temperatures reduce the cable's ability to dissipate heat, thereby reducing its ampacity.
• Installation Method/Grouping:
  • Conduit/Ducts: Cables run in enclosed conduits or ducts dissipate heat less efficiently than those in free air.
  • Direct Burial: Buried cables are affected by soil thermal resistivity.
  • Bundling/Grouping: When multiple current-carrying cables are run together in a bundle or conduit, their individual ampacities must be de-rated (reduced) because each cable contributes to the heating of the others, hindering heat dissipation.
• Voltage Drop: While not directly affecting ampacity, for long runs, the voltage drop along the conductor must also be considered to ensure the load receives adequate voltage.
• Importance: Strict adherence to established electrical codes and standards (which provide detailed ampacity tables based on these factors) is absolutely essential when selecting wire and cable sizes to ensure the safety and longevity of an electrical installation.