Buy IEC/TR Ed. Short-circuit currents in three-phase a.c. systems Part 4: Examples for the calculation of short-circuit currents from SAI Global. The results meet requirements of IEC and match the example provided in IEC TR section 6. The IEC standard terminology is used in the user. The International Electrotechnical Commission (IEC) is the leading global IEC TR , Short-circuit currents in three-phase a.c. systems – Part 4.

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Remote Currents and Voltages Currents flowing through sources, cables, lines, transformers and other equipment are also calculated.

IEC-60909 Short-Circuit in EasyPower

Impedance correction factors are applied for network or utility K Qgenerators K Gpower stations units with on-load tap changer K Spower stations units without on-load tap changer K SOand two- and three-winding transformers K T. I quality of writing IEC TR2- lire: For the short-circuit impedance of synchronous generators in the zero-sequence system, the following applies with KG from equation 1 8: The upstream circuit breakers do not trip instantaneously whereas the most 660909-4 circuit breaker trips fast, enabling selective coordination.

In the case of high-voltage feeders with nominal voltages above 35 kV fed by overhead lines, the equivalent impedance 2, may in many cases be considered as a reactance, i. For simplification, it is permitted to use the same value of Kas for the three-phase short circuit.

Ik Steady-state short-circuit current r. Transformers having different winding configurations, such as a delta connection on one side and a star wye 600909-4 on the other side, have a designated shift in the phase angles of currents and voltages.


Currents during two separate simultaneous single phase line-to-earth short circuits and partial short-circuit currentsflowing through earth IEC ,- Short-circuit current calculation in three-phase a. In a system of low voltage breakers with ZSI, when the current through any circuit breaker exceeds the short time pickup its restraining signal is sent to upstream circuit breakers.

Voltages and currents are to be converted by the rated transformation ratio t.

IEC Short-Circuit in EasyPower

Shift in current angle across delta-wye transformer Integration with Protective Device Coordination The IEC short-circuit results are integrated with the protective device coordination tools in 60990-4. NOTE The current in a three-phase short circuit is assumed to be made simultaneously in all poles.

Factors ;Iminand il,,for salient-pole generators Zero-sequence impedance arrangements for the calculation of unbalanced short-circuit currents are given in IEC Currents iiec two separate simultaneous single-phase line-to-earth short circuits and partial short-circuit currents following through earth IEC TR In this standard it is calculated using a factor m for the time- dependent heat effect of the d. The impedances and z o L of low-voltage and high-voltage cables depend isc national techniques and standards and may be taken from IEC or from textbooks or manufacturer’s data.

In special cases the zero-sequence equivalent short-circuit impedance of network feeders may need to be considered, depending on the winding configuration and the starpoint earthing of the transformer.


When calculating unbalanced short-circuit currents in medium- or high-voltage systems and applying an ice voltage source at the short-circuit location, the zero-sequence capacitances of lines and the zero-sequence shunt admittances are to be considered for isolated. Symmetrical locked-rotor current of an asynchronous motor Rated current of electrical equipment Thermal equivalent short-circuit current d.

This procedure is not allowed when calculating the peak short-circuit current i. For breaking current you can choose from 0. Remember me on 69009-4 computer. This will display the curve only up to the maximum current the device will see. Depending on the application of the results, it is of interest to know the r. I is not at all ci The following methods are supported for meshed networks as per section 4. For increased accuracy, equations 79, 76and 77 can be used.

They do not contribute to the symmetrical short-circuit breaking current I, and the steady-state short-circuit current I k.

IEC TR | IEC Webstore

Switches use the peak current to compare with making capacity. For other ,values of minimum time delay, linear interpolation between curves is acceptable. For the purpose of this standard, one has to make a distinction between short-circuit impedances at the ied location F and the short-circuit impedances of individual electrical equipment.