What factors determine the construction of different electrical cable types, and what are some examples of how application influences cable design?

Q: What factors determine the construction of different electrical cable types, and what are some examples of how application influences cable design?   A: The construction of electrical cable types is determined by multiple factors. Voltage rating is a key factor, with categories like Extra Low Voltage (below 70V), Low Voltage (up to 1000V), Medium Voltage (1000V to 35kV), High Voltage (35kV to 230kV), and Extra High Voltage (above 230kV). The insulation layer’s material type and thickness vary to meet electrical performance demands, and higher voltages may require additional layers per standards. Material properties such as conductivity, insulation resistance, and how they affect reactance, impedance, capacitance, and inductance also matter.   Application heavily influences design:   Overhead line wires need strength (to support weight between pylons/posts) and corrosion resistance but no material insulation (if contact/grounding risk is low).   Underground cables require insulation (against water ingress and mechanical damage) and often have metallic armour for direct burial protection.   Instrumentation cables (for data-sensitive areas) need metallic tape screening to protect against electromagnetic interference.   Fire performance cables (for fire safety systems like alarms/emergency lighting) must withstand fire and maintain functionality.   Cables for industries like mining (with harsh environments) use rubber insulation for flexibility and enhanced robustness against chemicals, along with protection like wire braiding/armouring.   Outdoor-used cables must be weather-resistant and handle sunlight/ozone. Additionally, cost and appearance (e.g., colour coding) have a secondary impact, with safe application being the primary concern.