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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Short Circuits in Power Systems: A Practical Guide to IEC 60909-0, 2nd Edition
When calculating short-circuit currents in systems with different voltage levels, it is necessary to transfer impedance values from one voltage level to another, usually to that voltage level at which the short-circuit current is to be calculated.
In general, two short-circuit currents, which differ in their magnitude, are to be calculated: In the case of high-voltage direct-current transmission systems, the capacitor banks and filters need special considerations, when calculating a.
The positive-sequence short-circuit impedance zat the short circuit location F is obtained according to figure 5a, when a symmetrical system of voltages of positive-sequence phase order is applied to the short-circuit location F, and all synchronous and asynchronous machines are replaced by their internal impedances.
CE1 TR–l read: I k autre s For dated references, subsequent amendments to, or revisions of, any of these publications do not apply.
Short-circuit current of a near-to-generator short circuit with decaying a. The symbols represent physical quantities possessing both numerical values and dimensions that are independent of units, provided a consistent unit system is chosen, for example the international system of units SI. The impedance of the network feeder and the transformer are related to the LV-side and the last one is also corrected with KT see 3. Currents calculated with equation 74 are larger than the real symmetrical short-circuit breaking.
For simplification, it is permitted to use the same value for IC as for the three- phase short circuit.
Special methods to calculate i, with sufficient accuracy are given in 4. The following values for the fictitious resistances RGfmay be used for the calculation of the peak short- circuit current with sufficient accuracy. This can lead to a situation where the partial short-circuit currents are too small to operate any further protection device, particularly in the case of minimum short-circuit currents.
The factor K shall, be calculated according to 4.
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The impedances in systems connected through transformers to the system, in ied the short circuit occurs, have to be 69009-0 by the square of the rated transformation ratio. Despite these assumptions being not strictly true for the power systems considered, the result of the calculation does fulfil the objective to give results which are generally of acceptable accuracy. Operational data and the load of consumers, tap- changer position of transformers, excitation of generators, and so on, are dispensable; additional calculations about all the different possible load flows at kec moment of short circuit are superfluous.
Calculation for a Load Circuit Thus the network feeder in figure 4a is represented by its internal impedance Zot, transferred to the LV-side of the transformer see 3. Short-circuit current of a far-from-generator short circuit with constant a.
These values cannot be used when calculating the aperiodic component id. Figure 2 – Short-circuit current of a near-to-generator short circuit with decaying a.
For the short-circuit impedance of synchronous generators in the zero-sequence system, the following applies with KG from equation 1 8: The initial symmetrical short-circuit currents riQ,, and riQm, on the high-voltage side of 69009-0 trans- former shall be given by the supply company or by an adequate calculation according to this standard.
Electrical equipment may be overstressed due to the short-circuit duration. For simplification, it is permitted to use the same value of Kas for the three-phase short circuit.
In existing low-voltage systems it is possible to determine the short-circuit impedance on the basis of measurements at the location of the prospective short circuit considered.
60990-0 For grounded systems the influence of motors on the line-to-earth short-circuit current cannot be neglected. The values are given in table 1 NOTE The introduction of a voltage factor c is necessary for various reasons.
Factor n for the heat effect of the a. Shunt admittances for example, line capacitances and passive loads are not to be considered when calculating short-circuit currents in accordance with figure 4b. Currents during two separate simultaneous single phase line-to-earth short circuits and partial short-circuit currentsflowing through earth IEC ,- Short-circuit current calculation in three-phase a.
IkP Steady-state short-circuit current at the terminals poles of a generator with compound excitation Initial symmetrical short-circuit current r. This first edition cancels and replaces IEC published in and constitutes a technical revision. Figure 3 – Characterization of short circuits 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.
Additional information may be found in IEC All network feeders, synchronous and asynchronous machines are replaced by their internal impedances see clause 3.