This Technical Report applies to low-voltage installations with a nominal system frequency of 50 Hz in which the circuits consist of insulated conductors@ cables or busbar trunking systems. It defines the different parameters used for the calculation of the characteristics of electrical wiring systems in order to comply with rules of HD 384/HD 60364. These rules are mainly the following: -current-carrying capacities of the conductors; -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; -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 60439-2 or powertrack systems according to EN 61534 series. The calculations provided in this Technical Report are only applicable where the characteristics of the circuits are known. For the purpose of this document@ when referring to Busbar Trunking Systems@ Powertrack Systems are also considered. NOTE 1 Mechanical stress during short-circuit is covered by IEC 60865. NOTE 2 In general these calculations concern supply by HV/LV transformer@ but they are also applicable to supply by LV/LV transformer and LV back-up generators. NOTE 3 Effects of harmonics currents are not covered by this document. 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@ crosssectional area of cables and characteristics for selection of busbar trunking systems with HD 384/HD 60364.