The Institute for Standardization of Bosnia and Herzegovina, through its Technical Committee BAS/TC 8, Insulation coordination, high voltage testing and instrument transformers, has adopted, by translation method, the third edition of BAS EN 60909-0:2026 Short-circuit currents in three-phase a.c systems - Part 0: Calculation of currents, which is a translation of the English version of EN 60909-0:2016.

BAS EN 60909-0:2026 is applicable to the calculation of short-circuit currents

-        in low-voltage three-phase AC systems and

-        in high-voltage three-phase AC systems,

operating at a nominal frequency of 50 Hz or 60 Hz. Systems with highest voltages of 550 kV and above that feature long transmission lines, are not within the scope of this standard.

This part of IEC 60909 establishes a general, practical and concise procedure leading to results which are generally of acceptable accuracy. For this calculation method, an equivalent voltage source at the short-circuit location is introduced. This does not include the use of special methods, for example the superposition method, ajusted to the particular circumstances, if they give at least the same precision. The superposition method gives the short-circuit current related to the one load flow presupposed. This method, therefore, does not necessarily lead to the maximum short-circuit current.

This part of IEC 60909 deals with the calculation of short-circuit currents in the case of balanced or unbalanced short circuits. A single line-to-earth fault is beyond the scope of this part of IEC 60909.

In general, two types short-circuit currents, which differ in their magnitude are considered:

-        the maximum short-circuit current, which determines the capacity or rating of electrical equipment; and

-        the minimum short-circuit current, which can be a basis, for example, for the selection of fuses, for the setting of protective devices and for checking the run-up of motors.

This part of IEC 60909 does not cover short-circuit currents deliberately created under controlled conditions (short-circuit testing stations).

The original texts of the standard were prepared by the International Technical Committee IEC/TC 73, Short-circuit currents.