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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This first edition cancels and replaces IEC published in and constitutes a technical revision. If the Joule integral or the thermal equivalent short-circuit current shall be calculated for unbalanced short circuits, replace I: The deviation depends on the configuration of the network. For grounded systems the influence of motors on the line-to-earth short-circuit current cannot be neglected.
The following types of unbalanced short circuits are treated in this standard: ILR highest symmetrical r. The influence of various winding-temperatures on RGf is not considered.
An example for the introduction of the correction factors of equation 13 to the positive-sequence and the zero-sequence system impedances of the equivalent circuits is given in 2. In all cases it is possible to determine the short-circuit current at the short-circuit location F with the help of an equivalent voltage source. Currents during two separate simultaneous single-phase line-to-earth short circuits and partial short-circuit currents following through earth IEC TR If the long-term operating conditions of network transformers before the short circuit are known for sure, then the following equation 12b may be used instead of equation 12a.
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Calculation with Impedance Corrections 609090- For two-winding transformers with and without on-load tap-changer, an impedance correction factor KT is to be introduced in addition to the impedance evaluated according to equations 7 to 9: The type of short circuit which leads to the highest short-circuit current depends on the values of the positive-sequence, negative-sequence, and zero-sequence short-circuit impedances of the system.
T k i and the factor K derived in 4. In this standard it is calculated using a factor m for the time- dependent heat effect of the d. Example for the estimation of the contribution from the asynchronous motors in relation to the total short-circuit current I quality of writing A,,, may be iex from figures 18 or 19 for cylindrical rotor generators or salient-pole generators.
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. Factors ;Iminand il,,for salient-pole generators Any divergence between the IEC Standard and the corresponding national or regional standard shall be clearly indicated in the latter.
E” Subtransient voltage of a synchronous machine f Frequency 50 Hz or 60 Hz Ib Symmetrical short-circuit breaking current r. Linand il,, factors for cylindrical rotor generators Calculation of a Generator 8. The estimation according to equation 28 is not allowed in the case of three-winding transformers.
Depending on the product f. Short-circuit current of a far-from-generator short circuit with constant a. Annex A forms an integral part of this standard. This part of IEC establishes a general, practicable and concise procedure leading to results, which are generally of acceptable accuracy.
Figure 2 – Short-circuit current of a near-to-generator short circuit with decaying a. For undated references, the latest edition of the normative document referred to applies. For a short circuit at the busbar B in figure 9, the partial short-circuit current of the low-voltage motor group M4 may be neglected, if the condition I,, I 0,Ol ICT3 holds.
Examples f o r the calculation of short-circuit currents’ IEC Connection Box to Service Panel The impedances and z o L of low-voltage and high-voltage cables depend on national techniques and standards and may be taken from IEC or from textbooks or manufacturer’s data. Electric and magnetic circuits IEC 15 1: He has more than 18 years of professional experience in planning and design of electrical power systems. This part of IEC does not deal with the calculation of short-circuit currents in installations on board ships and aeroplanes.
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. For balanced and unbalanced short circuits as shown in figure 3, it is useful to calculate the short-circuit currents by application of symmetrical components see 2.
The total short-circuit current in F1 or F2 figure 13 is found by adding the partial short-circuit current IL,, caused by the medium- and low-voltage auxiliary motors of the power station unit. I 1 unacceptable, marketing specialist other The peak short-circuit current i, at a short-circuit location F, fed from sources which are not meshed with one another, in accordance with figure 12, is the sum of the partial short-circuit currents: Electric and magnetic devices IEC It is assumed that the operating voltage at the terminals of the 6099-0 is equal to UrG.
Short Circuits in Power Systems: A Practical Guide to IEC 60909-0, 2nd Edition
Medium-voltage motors have to be considered in the calculation of maximum short-circuit current see 2. The equivalent voltage source is the only idc voltage of the system.
The factor K shall, be calculated according to 4. Method c is recommended in meshed networks see IEC