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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Figure 21 – Factor m for the heat effect of the d. The estimation according to equation 28 is not allowed in the case of three-winding transformers.

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Calculation of a Generator 8. Definitions,principles and rules IEC 1: Factor p for calculation of short-circuit breaking current 1, Nominal system voltage, line-to-line r. Methods of Calculations 1 1.

In this standard it is calculated using a factor m for the time- dependent heat effect of the d. Factors ;Iminand il,,for salient-pole generators The 60099-0 are given in table 1 NOTE The introduction of a voltage factor c is necessary for various reasons.

Calcul des courants Part O: Investigations of non-simultaneous short circuits, which may lead uec higher aperiodic components of short-circuit current, are beyond the scope of this standard. Rated voltage, line-to-line r.

The values of positive-sequence and negative-sequence impedances can differ from each other only in the case iev rotating machines. Factors for the calculation of short-circuit currents in three-phase a.

For the short-circuit impedances of synchronous generators in the negative-sequence system, the following applies with KG from equation 1 8: 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 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. In general, two short-circuit currents, which differ in their magnitude, are to be calculated: System diagram and equivalent circuit diagram for network feeders While using fuses or current-limiting circuit-breakers to protect substations, the initial symmetrical short- circuit current is first calculated as if these devices were not available.

For grounded systems the influence of 609909-0 on the line-to-earth short-circuit current cannot be neglected. For the effective reactance of the generators, introduce: In this case the Joule integral is determined from the characteristic of the current-limiting device. Calculation for an Industrial System The impedance correction factor shall be applied also to the negative-sequence and the iecc sequence impedance of the transformer when calculating unbalanced short-circuit currents.

The decaying aperiodic component id.

If the highest partial short-circuit current of the power station unit at the high-voltage side of the unit transformer with off-load taps is searched for, choose l-pT.

For higher temperatures than 20 OC, see equation 3. 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.

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

A,,, may be obtained from figures 18 or 19 for cylindrical rotor generators or salient-pole generators. Example for the estimation of the contribution from the asynchronous motors in relation to the total short-circuit current When calculating the partial short-circuit current I: The values of p in equation 70 apply if synchronous machines are excited by rotating exciters or by static converter exciters provided, for static exciters, the minimum time delay tminis less than 0,25 s and the maximum excitation voltage is less than 1,6 times rated load excitation-voltage.

Enter the exact the reason is: Any divergence between the IEC Standard and the corresponding national or regional standard shall be clearly indicated in the latter.

This postulates that the electrical equipment has a balanced structure, for example in the case of transposed overhead lines. The impedances of the equipment in superimposed or ief networks are to be divided or multiplied by the square of the rated transformation ratio t.