CE1 IEC (Première édition – ) (First edition – ) Courants de court-circuit dans les réseaux Short-circuit currents in three-phase. IEC Edition INTERNATIONAL. STANDARD. NORME. INTERNATIONALE. Short-circuit currents in three-phase a.c. systems –. Buy IEC SHORT-CIRCUIT CURRENTS IN THREE-PHASE A.C. SYSTEMS – PART 0: CALCULATION OF CURRENTS from SAI Global.
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Calculation for a Load Circuit From the calculated initial symmetrical short-circuit current and characteristic curves of the fuses or current-limiting circuit- breakers, the cut-off current is determined, which ie the peak short-circuit current of the 600909-0 substation. If there are several transformers with slightly differing rated transformation ratios trT1trT Characterization of short circuits and their currents Figure 3 – Characterization of short irc and their currents Figure 4 shows an example of the equivalent voltage source at the short-circuit location F as the only active voltage of the system fed by a transformer without or with on-load tap-changer.
Thus the network feeder in figure 4a is represented by its internal impedance Zot, transferred to the LV-side of the transformer see 3. For the short-circuit impedance of synchronous generators in the zero-sequence system, the following applies with KG from equation 1 8: The impedances and z o L of low-voltage and high-voltage cables depend on national techniques and standards and ieec be taken from IEC or from textbooks or manufacturer’s data. This standard does not cover short-circuit currents deliberately created under controlled conditions short-circuit testing stations.
Additional information may be found in IEC IEC Short-circuit currents in three-phase a c.
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Examples f o r the calculation of short-circuit currentsi The committee has decided that the contents of this publication will remain unchanged until This correction factor shall not be introduced for unit transformers of power station units see 3.
Any divergence between the IEC Standard and the corresponding national or regional standard shall be 6099-0 indicated in the latter.
If the Joule integral or the thermal equivalent short-circuit current shall be calculated for unbalanced short circuits, replace I: The effect of series capacitors can be neglected in the calculation of short-circuit currents, if they are equipped with voltage-limiting devices in parallel, acting if a short circuit occurs.
For the calculation of the partial short-circuit current I L 2 feeding into the short-circuit location F2, for example at the connection to the high-voltage side of the auxiliary transformer AT in figure 13, it is sufficient to take: For dated references, subsequent amendments to, or revisions of, any of these publications do not apply.
Example of a meshed network fed from several sources The impedance correction factor shall be applied also to the negative-sequence and the zero- sequence impedance of the transformer when calculating unbalanced short-circuit currents. I tables, charts, graphs, figures Figure 20 describes this situation with balanced and unbalanced short circuits with earth connection at the short-circuit location F.
CE1- Instead of: Remember me on this computer. In this case, the symmetrical short- circuit breaking current Ib is smaller than the initial symmetrical short-circuit current I,”. CE1 TR–I read: They do not contribute to the symmetrical short-circuit breaking current I, and the steady-state short-circuit current I k. Short-circuit current-limiting reactors shall be treated as a part of the short-circuit impedance. The calculation of low-voltage breaking currents after a time deiay tmingreater than 0,1 s is not included in this standard; generator manufacturers may be able to provide information.
Single-fed short circuits supplied by a transformer according to figure 4, may a priori be regarded as far- from-generator short circuits if X, 2 Ur, with XQ, calculated in accordance with 3. The factors m and n first appeared as Figures 12a and 12b of IEC and are identical to them.
For other ,values of minimum time delay, linear interpolation between curves is acceptable. In all cases I L is equal to Ikv,because the short circuits are far-from-generator short circuits see 1.
In meshed networks there are several direct-current time constants. As long as RIX remains smaller than 0,3 in all branches, it is not necessary to use the factor 1, Factors for the calculation of short-circuit currents in three-phase a.
For a synchronous generator use Rm see 3. It is assumed that the operating voltage at the terminals of the generator is equal to UrG.
Example for the estimation of the contribution from the asynchronous motors in relation to the total short-circuit current For large transformers the resistance is so small that the impedance may be assumed to consist only of reactance when calculating short-circuit currents. ILR highest symmetrical r. This occurs in the case of a far-from-generator short circuit. Depending on the product f.
When calculating the partial short-circuit current I: For simplification of the calculation, groups of motors including their connection cables may be combined to a single equivalent motor see motor M4 in figure 9. Calculation of an LV motor 8.
Short Circuits in Power Systems: A Practical Guide to IEC 60909-0, 2nd Edition
Factor p for calculation of short-circuit 6099-0 current 1, The equations 46 and 47 are given for the calculation of and in figure 3c: Automatic Disconnection for a TN System 56 6. Factor m for the heat effect of the d.
Depending on the application of the results, it is of interest to know the r. Using this method, the currents in each line conductor are found by superposing the currents of the three symmetrical component systems: The impedances of the equipment in superimposed or subordinated networks are to be divided or multiplied by the square of the rated transformation ratio t.