• Electrical Installation Guide
• Automation Solution Guide
• Technical publications (Cahiers Techniques)

Sizing and protection of conductors

Component parts of an electric circuit and its protection are determined such that all normal and abnormal operating conditions are satisfied. Each circuit is then studied in detail.
From the rated currents of the loads, the level of short-circuit current, and the type of protective device, the cross-sectional area of circuit conductors can be determined, taking into account the nature of the cableways and their influence on the current rating of conductors.
Before adopting the conductor size indicated above, the following requirements must be satisfied:
The voltage drop complies with the relevant standard
Motor starting is satisfactory
Protection against electric shock is assured

The short-circuit current Isc is then determined, and the thermal and electrodynamic withstand capability of the circuit is checked. These calculations may indicate that it is necessary to use a conductor size larger than the size originally chosen.

EIG-G-sizing-protection-conductors.pdf

Prewiew two pages of this chapter here: voltage drop.