PD IEC/TR 60909-4:2021

Short-circuit currents in three-phase AC systems. Examples for the calculation of short-circuit currents | Status: Current

1 Scope This part of IEC 60909, which is a Technical Report, is 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 AC systems. This document does not include additional requirements but gives support for the modelling of electrical equipment in the positive-sequence, the negative-sequence and the zero-sequence system (Clause 4), the practical execution of calculations in a low-voltage system (Clause 5), a medium-voltage system with asynchronous motors (Clause 6) and a power station unit with its auxiliary network feeding a large number of medium-voltage asynchronous motors and low-voltage motor groups (Clause 7). The three examples given in Clauses 5, 6 and 7 are similar to those given in IEC TR 60909‑4:2000 but they are revised in accordance with IEC 60909‑0, which replaces it. The example given in Clause 8 is new and mirrors the introduction of the new 6.8 of IEC 60909‑0:2016. Clause 9 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 " , ip, Ib, Ik , I k 1 " and ip1 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.