prHD 50480

Determination of cross-sectional area of conductors and selection of protective devices

Scope

This Technical Report provides methods and guidance to determine parameters of low-voltage electrical installations necessary for the proper selection of conductors and protective devices in compliance with HD 60364.
It applies to 50Hz AC LV electrical installations.
Methods and guidance are provided for:
— current-carrying capacities of the conductors;
NOTE 1 Effects of harmonics currents are not covered by this document.
— characteristics of protective devices in regard to protection against overcurrent;
— verification of thermal stress in conductors due to short-circuit current or earth fault current;
NOTE 2 Mechanical stress during short-circuit is covered by IEC 60865.
— fault protection (protection against indirect contact) in TN systems and IT systems;
— limitation of voltage drop;
— verification of mechanical stresses during short-circuit in busbar trunking systems (BTS) according to EN 61439-6 or powertrack systems (PTS) according to EN 61534 series.
— verification of thermal and mechanical stresses of switching devices (e.g switch-disconnector, contactor)
The calculations provided in this Technical Report are only applicable where the characteristics of the circuits are known.
This Technical Report is also applicable for checking the compliance of the results of calculations performed by software programs for calculation of cross-sectional area of insulated conductors, cross-sectional area of cables and characteristics for selection of busbar trunking systems with HD 60364.