Download Citation on ResearchGate | Applying IEC , Fault Current Calculations | Rather than the short-circuit current that would occur in a specific. Applying IEC , short-circuit current calculations. Abstract: Rather than the short-circuit current that would occur in a specific instance, IEC derives. The initial short circuit current for a is as per IEC Equation

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Calculation of short-circuit currents of asynchronous motors in the case of a short circuit at the terminals see 4.

The impedance correction factor shall be applied also to the negative-sequence and the zero- sequence impedance of the transformer when calculating unbalanced short-circuit currents. The object of the IEC is to promote international co-operation on all questions concerning standardization in the electrical and electronic fields. For these equivalent asynchronous motors, including their connection cables, the following may be used: IEC section 6 provides a sample calculation as a benchmark test for software programs to compare.

That is why it is not possible to give an easy method of calculating i, and id. This first edition cancels and replaces IEC published in and constitutes a technical revision.

Low-voltage motors are to be taken into account in auxiliaries of power stations and in industrial and similar installations, for example in networks of chemical and steel industries and pump- stations. Linand il,, factors for cylindrical rotor generators 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.

As a falculation, reversible static converter-fed drives are treated for the calculation of short-circuit currents in a similar way as asynchronous motors. The resistance is to be considered if the peak short-circuit current ip or the d.

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For simplification, it is permitted to use the same value for as for the three- phase short circuit. I cochez tout ce qui convient Je suis lehn: These values cannot be used when calculating the aperiodic component id.

The short-circuit impedances for electrical equipment are modified using circyit corrections factors that are calculated based on section 3. Breaking currents are calculated at 0.

### IEC Short-Circuit in EasyPower

This correction factor shall not be introduced for unit transformers of power station units see 3. ILR highest symmetrical r. I In the case of minimum steady-state calculatkon circuits introduce c see 2.

Figure 21 – Factor m for the heat effect of the d. It is assumed that the operating voltage at the terminals of the generator is equal to UrG. Asymmetrical ie for the initial and the four breaking time intervals are also calculated for use in protective device coordination.

In this case, the symmetrical short- circuit breaking current Ib is smaller than the initial symmetrical short-circuit current I,”. Switches use the peak current to compare with making capacity. Rated short-circuit voltage calculatioh 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 snort respectively quadrature axis Fictitious reactance of a generator with compound excitation in the case of steady-state short circuit at the terminals poles Xd resp.

Circuiy f o r the calculation of short-circuit currents’ IEC Ikpis the steady-state short-circuit current of a generator at a three-phase terminal short-circuit.

## IEC-60909 Short-Circuit in EasyPower

Calcul des courants Part O: 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. Phasor diagram of a synchronous generator at rated conditions Each branch short- circuit current can be calculated as an independent single-source three-phase short-circuit current in accordance with equation 29 and the information given in 4. In this case, it is necessary to distinguish between networks with and without parallel branches see 4.

Ik Steady-state short-circuit current r.

The initial short-circuit current at the short-circuit location F is the phasor sum of the individual partial short-circuit currents see figure They do not contribute to the symmetrical short-circuit breaking current I, and the steady-state short-circuit current I k.

Thus the network feeder in figure 4a is represented by its internal impedance Zot, transferred to the LV-side of the transformer see 3. When using this method in meshed networks with transformers, generators and power station units, the impedance correction factors KT,KG and Ks, respectively Kso, shall be introduced with the same values as for the 50 Hz or 60 Hz calculations.

The IEC standard terminology is used in the user interface and reports.

Electrical equipment may be overstressed due to the short-circuit duration. 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.

CE1 TR2– Instead of: For rotating machines the current contributions to short-circuit decays over time. Short-circuit duty results calculagion in the single line drawing Table 5: For the calculatiob 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. For phase TCC clipping and tick marks, EasyPower automatically selects the asymmetrical currents for low voltage circuit breakers, fuses and electromechanical relays.