IEC 60909-4 PDF

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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Short-circuit on any bus results in voltage drop in other near buses in the system.

IEC Short-Circuit in EasyPower

Sequential short circuits are not considered. The factors m and n first appeared as Figures 12a and 12b of IEC and are identical to them.

Q5 This standard meets my needs: Zero-sequence impedance arrangements for 660909-4 calculation of unbalanced short-circuit currents are given in IEC They do not contribute to the symmetrical short-circuit breaking current I, and the steady-state short-circuit current I k. For phase currents, the maximum current of the three phases is used. Line-to-earth short-circuit currents for Initial symmetrical rms and peak Short-Circuit Duty Calculations EasyPower compares the short circuit results with protective device short-circuit ratings and displays the results in the text report and in the single line diagram.

It is assumed that the operating voltage at the terminals of the generator is equal to UrG. Shunt admittances for example, line capacitances and passive loads are not to be considered when calculating short-circuit currents in accordance with figure 4b.

I education ci military ci I other If not, they are subject to additional considerations. You can enter equipment data and parameters via user friendly interface. EasyPower applies impedance correction factors in short circuit calculation based on IEC standard. That is why it is not possible to give an easy method of calculating i, and id. For the short-circuit impedance of synchronous generators in the zero-sequence system, the following applies with KG from equation 1 8: You can set a voltage sensitivity threshold in the options eic that any bus with voltage below this 6090-94 will be highlighted red in the single line view and shown in the voltage sensitivity report.


The resistive component uRrcan be calculated from the total losses PkiTin the windings at the rated current IrT, both referred to the same transformer side see equation 8. IEC TR2- lire: The need for the calculation of minimum short-circuit currents may arise because of underexcited operation of generators low-load condition in cable systems or in systems including long overhead lines, hydro pumping stations.

The following 6099-4 are lec. Calculation of currents 1 60909- 1. I k autre s These have, 90, and ice degrees phase shift respectively based on the high voltage side taken as the reference. Thus the network feeder in figure 4a is represented by its internal impedance Zot, transferred to the LV-side of the transformer see 3. However, parties to agreements based on this part of IEC are encouraged to investigate the possibility of applying the most recent editions of 60990-4 normative documents indicated below.

The program is designed to address short-circuits in meshed networks.

Factor p for calculation of short-circuit breaking current 1, The equations 46 and 47 are given for the calculation of and in figure 3c: Special methods to calculate i, with sufficient accuracy iecc given in 4.


The EasyPower library is populated with data for circuit breakers, fuses and switches.

For undated references, the kec edition of the normative document referred to applies. With respect to equation 99 in table 3 the steady-state short-circuit current of asynchronous motors is zero in the case of a three-phase short circuit at the terminals figure 12 and equation This part of IEC deals with the calculation of short-circuit currents in the case of balanced or unbalanced short circuits.

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For remote buses and branches across transformers, a phase angle shift is applied accordingly isc the short circuit calculations. The decaying aperiodic component id. In the case of figure 4, for instance, to the LV side.

For TCC clipping you can choose one from initial, breaking and steady state currents. You can also view the remote branch currents and remote bus voltages. IEC Short-circuit currents in three-phase a c.

IEC-60909 Short-Circuit in EasyPower

For high voltage circuit breakers, the peak current is compared with the making capacity and the breaking current is 60099-4 with the rated breaking capacity. Currents during two separate simultaneous single-phase line-to-earth short circuits and partial short-circuit currents following through earth IEC TR Special considerations are necessary in this case, for instance with the superposition method.

Depending on the application of the results, it is of interest to know the r.