Chapter G

Sizing and protection of conductors

Determination of voltage drop

From Electrical Installation Guide
HomeSizing and protection of conductorsDetermination of voltage drop

The impedance of circuit conductors is low but not negligible: when carrying load current there is a voltage drop between the origin of the circuit and the load terminals. The correct operation of a load (a motor, lighting circuit, etc.) depends on the voltage at its terminals being maintained at a value close to its rated value. It is necessary therefore to determine the circuit conductors such that at full-load current, the load terminal voltage is maintained within the limits required for correct performance.

This section deals with methods of determining voltage drops, in order to check that:

  • They comply with the particular standards and regulations in force
  • They can be tolerated by the load
  • They satisfy the essential operational requirements