What is the Cable Selection methods ?

Cables should be selected and used such that the product does not present an unacceptable risk or danger to life or property when used in its intended manner.
Cables should also be selected so that they are suitable for the operating environment conditions e.g. use in petrochemical works, need for fire performance, the need for protection
against attack by rodents, termites, etc, equipment classification and any other external influences which may exist. They should also be selected according to the appropriate
rated voltage and the cross-sectional area of every conductor such that its current carrying capacity is not less than the maximum sustained current which would normally flow
through it, and the short circuit current rating of conductor and screen is adequate for the prospective short circuit and time for which it persists. In addition, consideration should be given to other relevant factors, such as:

• voltage drop requirements
• operating characteristics of connected equipment
• economics

source : prysmian

Principles of Cable Sizing Calculations
1. Introduction

Cable (or conductor) sizing is the process of selecting appropriate sizes for electrical power cable conductors. Cable sizes are typically decribed in terms of cross-sectional area, American Wire Gauge (AWG) or kcmil, depending on geographic region.

The proper sizing of cables is important to ensure that the cable can:

    Operate continuously under full load without being damaged
    Provide the load with a suitable voltage (and avoid excessive voltage drops)
    Withstand the worst short circuits currents flowing through the cable

Cable sizing methods do differ across international standards (e.g. IEC, NEC, BS, etc) and some standards emphasise certain things over others. However the general principles that underpin all cable sizing calculation do not change. When sizing a cable, the following general process is typically followed:

    Gather data about the cable, its installation conditions, the load that it will carry, etc
    Determine the minimum cable size based on ampacity (continuous current carrying capacity)
    Determine the minimum cable size based on voltage drop considerations
    Determine the minimum cable size based on short circuit temperature rise
    Select the cable based on the highest of the sizes calculated in the steps above