scope:

Scope and object

This part of IEC 60909 is a technical report intended to give help for the application of IEC 60909-0 for the calculation of short-circuit currents in 50 Hz or 60 Hz three-phase a.c. systems.

This technical report does not include additional requirements but gives support for the modelling of electrical equipment in the positive-sequence, the negative-sequence and the zerosequence system (clause 2) and the practical execution of calculations in a low-voltage system (clause 3), a medium-voltage system with asynchronous motors (clause 4) and a power-station unit with its auxiliary network feeding a large number of medium-voltage asynchronous motors and low-voltage motor groups (clause 5).

The three examples given in clauses 3, 4 and 5 are similar to those given in IEC 60909 (1988) but they are revised in accordance with IEC 60909-0, which replaces it.

A subclause is added to the example in clause 3 to give a comparison between the results found with the application of the equivalent voltage source at the short-circuit location following the procedure given in IEC 60909-0 on the one hand, and results found with the superposition method on the other hand, taking into account different load-flow conditions before the short circuit.

Clause 6 of this technical report gives the circuit diagram and the data of a test network and the results for a calculation carried out in accordance with IEC 60909-0, to offer the possibility for a comparison between the results found with a digital program for the calculation of short-circuit currents and the given results for I"_k, i_p, I_b, I_k, I"_k1 and i_p1 in a high-voltage network with power-station units, generators, asynchronous motors and lines in four different voltage levels 380 kV, 110 kV, 30 kV and 10 kV.