### IEC 60909 PDF

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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Impedances 2, between the starpoint of transformers and earth are to be introduced as 3 2, into the zero-sequence system without a correction factor. U, is the nominal voltage of the system; ur, 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 The effective resistance of the stator of synchronous machines lies generally much below the given values for RGf.

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 the moment of short circuit are superfluous. The resistance is to be considered if the peak short-circuit current ip or the d. Depending on the application of the results, it is of interest to know the r. Examples f o r the calculation of short-circuit currents’ IEC 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.

## IEC-60909 Short-Circuit in EasyPower

In general, the calculation according to 4. Short-circuit current-limiting reactors shall be treated as a part of the short-circuit impedance. Short-circuit impedances 6090 a three-phase a. 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. The factor K shall, be calculated according to 4.

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Investigations of non-simultaneous short circuits, which may lead to higher aperiodic components of short-circuit current, are beyond the scope of this standard. Q5 This standard meets my needs: T JSrT ; t, is the rated transformation ratio of the unit transformer: For simplification, it is permitted to use the same value for as for the three- phase short circuit. With respect to equation 99 in table 3 the steady-state short-circuit current of asynchronous motors is zero in the case of a three-phase short circuit at the terminals figure 12 and equation This procedure is not allowed when calculating the peak short-circuit current i.

For jec with delta and start wye winding connections, the clock notations 1,3,5,7,9 and 11 are supported in the database. You can obtain iex following values of short-circuit currents at the fault location for both maximum and minimum short circuit currents:. EasyPower provides the option of showing a warning when the short-circuit duty percent is above a user defined safety margin threshold but below the violation level. Calculation for a Load Circuit The calculation of low-voltage breaking currents after a time deiay tmingreater than 0,1 s is not included in this standard; generator manufacturers may be able to provide information.

The influence of various winding-temperatures on RGf is not considered.

The superposition method gives the short-circuit current related to the one load flow presupposed. Earth ground trip functions for low voltage circuit breakers or relays use the symmetrical earth iev current.

DC component of short-circuit current at breaking times: Then they contribute only to the initial symmetrical short-circuit current I: The initial short-circuit current at the short-circuit location F is the phasor sum of the individual partial short-circuit currents see figure 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. Thus the network feeder in figure 4a is represented by its internal impedance Zot, transferred to the LV-side of the transformer see 3. Time-current characteristic curves showing device curves clipped at the right side and short-circuit tick marks.