This calculation is based on IEC (, c), “Short-circuit currents in three-phase a.c. systems – Part 0: Calculation of currents” and. EasyPower offers a complete and accurate solution to short-circuit calculations in three-phase AC systems using the IEC standard. You can enter. IEC Edition INTERNATIONAL. STANDARD. NORME. INTERNATIONALE. Short-circuit currents in three-phase a.c. systems –.

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EasyPower uses the following c factors as the default for maximum and minimum short-circuit conditions. As a result, reversible static converter-fed drives are treated for the calculation of short-circuit currents in a similar way as asynchronous motors. Factor q for the calculation of the symmetrical short-circuit breaking current of asynchronous motors The generator impedance shall be transferred to the high-voltage side using the rated transformation ratio t.

Transformer Impedance Correction Factors The transformer correction factor K T for two winding units with or without on-load tap changer LTC is calculated as follows per section 3.

You are currently using the site but have requested a page in the site. This figure is useful for information but should not be used instead of I calculation. Short Circuits in Power Systems: It is not necessary for the product 1, Short-circuit duty results displayed in the single line drawing Table 5: Synchronous Generator Impedance Correction Factor The synchronous generator impedance correction factor K G for generators without unit transformers is calculated as follows per section 3.

Calculation of a Cable 8.

This first edition cancels and replaces IEC published in and constitutes a technical revision. The short-circuit impedances for electrical equipment are modified using impedance corrections factors that are calculated based on section 3.

In the case of a near-to-generator short circuit, the short-circuit current can be considered as the sum of the following two components: Enter the exact the reason is: Figure 2 – Short-circuit current of a near-to-generator short circuit with decaying a. The initial symmetrical short-circuit currents riQ,, and riQm, on the high-voltage side of the trans- former shall be given by the supply company or by an adequate calculation according to this standard.

### IEC Short-Circuit in EasyPower

For TCC clipping you can choose one from initial, breaking and steady state currents. View of the single line diagram in the time current characteristics TCC plot for protective devices. Voltages at remote buses are also provided. Factor q may also be obtained from figure All other active voltages in the system are assumed to be zero.

## Short Circuits in Power Systems: A Practical Guide to IEC 60909-0, 2nd Edition

The zero-sequence system impedance Z,, of the motor shall be given by the manufacturer, if needed see 4. For the purpose of this standard, one has to make a distinction between short-circuit impedances at the short-circuit location F and the short-circuit impedances of individual electrical equipment.

For undated references, the latest edition of the normative document referred to applies. Examples f o r the calculation of short-circuit currentsi The committee has decided that the contents of this publication will remain unchanged until If the highest partial short-circuit current of the power station unit at the high-voltage side of the unit transformer with ieec taps is searched for, choose l-pT.

### IEC | IEC Webstore

For the calculation of the initial short-circuit currents according to 4. 6090 values of positive-sequence and negative-sequence impedances can differ from each other only in the case of rotating machines.

With these impedances the corrected equivalent impedances LK, z B K and ZCKshall be calculated using the procedure given in equation i i. Transformer secondary short 660909. This is admissible, because the impedance correction factor KTfor network transformers is introduced. For the short-circuit impedances of synchronous generators in the negative-sequence system, the following applies with KG from equation 1 8: The correction factor Kso shall also be applied to the zero-sequence system impedance of the power station unit excepting, if present, iiec impedance component between the star point of the transformer and earth.

You can modify these values as needed in the short circuit options.

Calculation of an LV motor 8. Calculations are simplest for balanced short circuits on radial systems, as the individual contributions to a balanced short circuit can be evaluated separately for each source figures 12 or The zero-sequence short-circuit impedance at the short-circuit location F is obtained according to figure 5c, if an a. Neglecting the -zero-sequence capacitances of lines in earthed neutral systems leads to results which are slightly higher than the real values of the short-circuit currents.

Calculated Values You can obtain the following values of short-circuit currents at the fault location for both maximum and minimum short circuit currents: Short-circuit current of a far-from-generator short circuit with constant a.

## IEC-60909 Short-Circuit in EasyPower

The capacitances of lines overhead lines and cables of low-voltage networks may be neglected in the positive- negative- and zero-sequence system.

If the Joule integral or the thermal equivalent short-circuit current shall be calculated for unbalanced short circuits, replace I: Switches use the peak current to compare with making capacity. NOTE Equivalent circuits of the positive-sequence and the zero-sequence system are given in IECtable Iitem 4 to 7 for different cases of starpoint earthing.