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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The equations 46 and 47 are given for the calculation of and in figure 3c: This correction factor shall not be introduced for unit transformers of power station units see 3.
Within the accuracy of this standard, it is often sufficient to determine the short-circuit current at the short-circuit location F idc being the sum of the absolute values of the individual partial short- circuit currents. Ratings for HV breaker in project file loaded from the library In the equipment short-circuit duty report, comments and text colors provide indication of problem areas. Asymmetrical currents are calculated as the root mean square of the symmetrical and dc components.
A,,, may be obtained from figures 18 or 19 for cylindrical rotor generators or salient-pole generators. Calcul des courants Short-circuit currents in three-phase a.
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. I education ci military ci I other The IEC short-circuit results are integrated with the protective device coordination tools in EasyPower. U nQ is the nominal system voltage at the feeder connection point Q of the power station unit. 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.
The text of this standard is based on the following documents: The deviation depends on the configuration of the network. Proof of Protective Measures Annex A forms an integral part of this standard.
The equivalent voltage source is the only active voltage of the system. In the case of figure 4, for instance, to the LV side. The IEC shall not be held responsible for identifying any or all such patent rights.
Calculation of an LV motor 8. Automatic Disconnection for a TN System 56 6.
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The short-circuit current through any protective device can be used to clip the TCC curve of the device. Line-to-earth short-circuit currents for Initial symmetrical rms and peak Short-Circuit Duty Calculations EasyPower compares the short circuit results with protective device short-circuit ratings and displays the results in the text report and in the single iwc diagram.
Enter the email address you signed up with and we’ll email you a reset link. T JSrT ; t, is the rated transformation ratio of the unit transformer: Any divergence between the IEC Standard and the corresponding national or regional standard shall be clearly indicated in the latter. For simplification, it is permitted to use the same value for IC as for the three- phase short circuit. While using fuses or current-limiting circuit-breakers to protect substations, the initial symmetrical short- circuit current 60990 first calculated as if these devices were not available.
If the long-term 6909 conditions of network transformers before the short circuit are known for sure, then the following equation 12b may be used instead of equation 12a.
Ikpis the steady-state short-circuit current of a generator at a three-phase terminal short-circuit. Examples f o r the calculation of short-circuit currentsi The committee has decided that the contents of this publication will remain unchanged until For large transformers the resistance is so small that the impedance may be assumed to consist only of reactance when calculating short-circuit currents.
The voltage factor c is used to scale the equivalent voltage source in the calculations to account for variations in the system voltage. EasyPower supports the following four types of short-circuit conditions as per IEC Description Reflecting the changes to the all-important short circuit calculations in three-phase power systems according to IEC standard, this new edition of the practical guide retains its proven and unique concept of explanations, calculations and real-life examples of short circuits in electrical networks.
EasyPower provides the necessary phase angle shift of remote voltages and currents for IEC rated transformers in the IEC short circuit analysis. The method described above is for 3-phase short circuit. Rated short-circuit voltage of a transformer in per cent Short-circuit voltage of a short-circuit limiting reactor in per cent Rated resistive component of the short-circuit voltage of a transformer in per cent Rated reactive component of the short-circuit voltage of a transformer in per cent Positive- negative- zero-sequence voltage Reactance, absolute respectively relative value Synchronous reactance, direct axis respectively quadrature axis Fictitious reactance iecc a generator with compound excitation in the case of steady-state short circuit at the terminals poles Xd resp.
If the Joule integral or the thermal equivalent short-circuit current shall be calculated for unbalanced 660909 circuits, replace I: The EasyPower library is populated with data for circuit breakers, fuses and switches. NOTE For some near-to-generator short circuits the value of id. Calculation of Short-Circuit Currents IkP Steady-state short-circuit current at the terminals poles of a generator with compound excitation Initial symmetrical short-circuit current r.
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. The short-circuit impedances for ie equipment are modified using impedance corrections factors that are calculated based on section 3.
IEC standard specifies clock number notation and their respective phase angle shift for transformers. For the examples in figures 1Ib and 1 IC, the initial symmetrical short-circuit current is calculated with the corrected impedances of the generator and the power station unit see 3.
IEC-60909 Short-Circuit in EasyPower
The initial symmetrical current is calculated 06909 on section 4. I tables, charts, graphs, figures The impedances in systems connected through transformers to the system, in which the short circuit occurs, have to be transferred by the square of the rated transformation ratio. 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.