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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NOTE Equivalent circuits of the positive-sequence and the zero-sequence system are given in IECtable Iitem 4 to 7 60990 different cases of starpoint earthing.
The value should be obtained from the manufacturer. Xk may be neglected. Steady-state short-circuit current I k is calculated based on section 4.
For simplification, it is permitted to 6099 the same value for IC as for the three- phase short circuit. For phase TCC clipping and tick marks, EasyPower automatically selects the asymmetrical currents for low voltage circuit breakers, fuses and electromechanical relays. Proof of the Stability of Low-Voltage Systems Remote Currents and Voltages Currents flowing through sources, cables, lines, transformers and other equipment are also calculated.
Skip to main content. The IEC standard terminology is used in the user interface and reports. ief
IEC Short-Circuit in EasyPower
During the initial stage of the short circuit, the negative impedance is approximately equal to the positive-sequence impedance, independent of whether the short circuit is a near-to-generator or a far-from-generator short circuit. For a synchronous generator use Rm see 3.
Proof of Protective Measures Definitions,principles and rules IEC 1: The three impedance correction factors given in equation 13 shall be introduced also to the negative-sequence and to the zero-sequence systems of the three-winding transformer.
IEC TR2- lire: Calculation of short-circuit currents of asynchronous motors in the case of a short circuit at the terminals see 4.
O 1 marks the positive-sequence neutral reference. This is the first step to obtaining most values. The resistive component uRrcan be calculated from the iwc losses PkiTin the windings at the rated current IrT, both referred to the same transformer side see equation 8.
Voltages at remote buses are also provided.
Characterization of short circuits and their currents Normally, the steady-state short-circuit current Ik is smaller than the symmetrical short-circuit breaking current 1. In this case, the iex short- circuit breaking current Ib is smaller than the initial symmetrical short-circuit current I,”.
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The factors m and n first appeared as Figures 12a and 12b of IEC and are identical to them. A contribution is also given if, in case of a power station unit, the short-circuit occurs on the high-voltage side of the unit transformer see figure 1lc.
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I In the case of minimum steady-state short circuits introduce c see 2. If only overexcited operation is expected, then 609909 the calculation of unbalanced short-circuit currents the correction factor Ks from equation 22 shall be used for both the positive-sequence and the negative-sequence system impedances of the power station unit. This is possible if the d.
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.
Automatic Disconnection for a TN System 56 6. The generator impedance shall be transferred to the high-voltage side using the rated transformation ratio t. This is the only active voltage of the network 1.
IEC-60909 Short-Circuit in EasyPower
This method applies the 1. U, is the nominal voltage of the system; isc, is the rated voltage of the generator; ZGK is the corrected subtransient impedance of the generator; 2, is the subtransient impedance of the generator in the positive-sequence system: Calculations are simplest for balanced short circuits on radial systems, as the individual contributions to a balanced short circuit can be evaluated separately for each source figures 12 or Calculation for an Industrial System In some special cases, it could happen that the decaying short-circuit current reaches zero for the first time, some cycles after the short circuit took place.
Short-circuit current-limiting reactors shall be treated as a part of the short-circuit impedance.
Kec figure is useful for information but should not be used instead of I calculation. Factors for the calculation of short-circuit currents in three-phase a. 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 is the peak short-circuit current of the downstream substation.
Systems at highest voltages of kV iev above with long transmission lines need special consideration. The impedance of the auxiliary transformer AT in figure 13 is to be corrected with KT from 3.