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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You can view the currents in various formats such as phase currents for A, B and C phases or in symmetrical components: Factor p for calculation of short-circuit breaking current 1, The text of this standard is based on the following documents: This fault is beyond the scope of, and is therefore not dealt with in, 60099 standard.

## Short Circuits in Power Systems: A Practical Guide to IEC 60909-0, 2nd Edition

Calculated Values You can obtain the following values of short-circuit currents at the fault location for both maximum and minimum short circuit currents: 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.

Calculation of a Cable 8. If there are several transformers with slightly differing rated transformation ratios trT1trT For the purpose of this standard, one has to make a distinction between short-circuit impedances at the short-circuit location F and the short-circuit impedances of individual electrical equipment. 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 following features are supported: Transformers having different winding configurations, such as a delta connection on one side and a star wye connection on the other side, have a designated shift in the phase angles of currents and voltages.

Regardless of the time of short-circuit occurrence, the discharge current of the shunt capacitors may be neglected for the calculation of the peak short-circuit current. The resistance is to be considered if the peak short-circuit current ip or the d.

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 609909 to the short-circuit location F, and all synchronous and asynchronous machines are replaced by their internal impedances.

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The short circuit rating is part of the data library. Fuses and low voltage circuit breakers ratings are compared with initial currents.

## IEC-60909 Short-Circuit in EasyPower

These values cannot be used when calculating the aperiodic component id. Neglecting the -zero-sequence capacitances of lines in earthed neutral systems leads to results which are slightly higher than the real values of the short-circuit currents.

In general, the calculation according to 4. Additional information 60099 be found in IEC Asymmetrical Currents Asymmetrical currents for the initial and the four breaking time intervals are also calculated for use in protective device coordination. For currents during two separate simultaneous single-phase line-to-earth short circuits in an isolated neutral system or a resonance earthed neutral system, see IEC I librarian iiec I design engineer safety engineer ci Q7 Please assess the standard in the I following categories, using testing engineer ci the numbers: Voltages at remote buses are also provided.

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. If only overexcited operation is expected, then for 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.

Voltage Factors c The voltage factor c is used to scale the equivalent voltage source in the calculations to account for variations in the system voltage. That is why it is not possible to give an easy method of calculating i, and id.

The effect of series capacitors can be neglected in the calculation of short-circuit currents, if they are equipped with voltage-limiting devices in parallel, acting if a short circuit occurs.

For simplification, it is permitted to use the same value for IC as for the three- phase short circuit. Iex system voltage, line-to-line r.

### IEC Short-Circuit in EasyPower

Three-phase short-circuit currents for breaking I b at0. As a result, reversible static converter-fed drives are treated for the calculation of short-circuit currents in a similar way as asynchronous motors.

I,, is the rated current of the generator transferred to the high-voltage side see 4. The impedance of the auxiliary transformer AT in figure 13 is 6909 be corrected with KT from 3.

This method, therefore, does not necessarily lead to the maximum short-circuit current. Linand il,, factors for cylindrical rotor generators Impedances between a starpoint and earth shall be introduced without correction factor. Any branch may be a series combination of several impedances. For balanced and unbalanced short circuits as shown in figure 3, it is useful to calculate the short-circuit currents by application of symmetrical components see 2.

The type of short circuit which leads to the highest short-circuit current depends on the values of the positive-sequence, negative-sequence, and zero-sequence short-circuit impedances of the system. For a short circuit at the busbar B in figure 9, the ied short-circuit current of the low-voltage motor group M4 may be neglected, if the condition I,, I 0,Ol ICT3 holds.