Buy IEC/TR Ed. Short-circuit currents in three-phase a.c. systems Part 4: Examples for the calculation of short-circuit currents from SAI Global. The results meet requirements of IEC and match the example provided in IEC TR section 6. The IEC standard terminology is used in the user. The International Electrotechnical Commission (IEC) is the leading global IEC TR , Short-circuit currents in three-phase a.c. systems – Part 4.

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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 line diagram.

## IEC TR 60909-4:2000

O 1 marks the positive-sequence neutral reference. Example HV breaker ratings in the device library Figure 4: Figure 21 – Factor m for the heat effect 69009-4 the d. For three-winding transformers with and without on-load tap-changer, three impedance correction factors can be found using the relative values of the reactances of the transformer see 3.

Ik Steady-state short-circuit current r. IEC TR2 609094- – lire: The following features are supported:. Depending on the 6009-4 of the results, it is of interest to know the r. As a result, reversible static converter-fed drives are treated for the calculation of short-circuit currents in a similar way as asynchronous motors.

The total short-circuit in F1 or F2 figure 13 is found by adding the partial short-circuit current ILrnv, caused by the medium- and low-voltage auxiliary motors of the power station unit.

The synchronous generator impedance correction factor K G for generators without unit transformers is calculated as follows per section 3. In this case special considerations beyond the scope and procedure given in this 609094 have to be taken into account see for instance 2.

If Si is used in spite of this in connection with short-circuit calculations, for instance to calculate the internal impedance of a network feeder at the connection point Q, then the definition given should be used in the following form: The capacitances of lines overhead lines and cables of low-voltage networks may be neglected in the positive- negative- and zero-sequence system.

The following features are supported: Breaking currents are calculated at 0. Annex A forms an integral part of this standard.

This standard does not cover short-circuit currents deliberately created under controlled conditions short-circuit testing stations. These values cannot be used when calculating the aperiodic component id. In a near-to-generator short circuit, the short-circuit current behaves generally as shown in figure 2. If synchronous motors have a voltage regulation, they are treated like synchronous generators. They may be neglected. Figure 1 – Isc current of a far-from-generator short circuit with constant a.

A,,, may be obtained from figures 18 or 19 for cylindrical rotor generators or salient-pole generators.

When using this method in meshed networks with transformers, generators and iiec 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. Log In Sign Up. Symmetrical currents are applied for relays with DC offset filter.

### IEC TR | IEC Webstore

Xk may be neglected. You can also view the remote branch currents and remote bus voltages. Iecc admittances for example, line capacitances and passive loads are not to be considered when calculating short-circuit currents in accordance with figure 4b.

In the case of high-voltage direct-current transmission systems, the capacitor banks and filters need special considerations, when calculating a. For two-winding transformers with and without on-load tap-changer, an impedance correction factor KT is to be introduced in addition to the impedance evaluated according to equations 7 to 9: If the long-term operating conditions of network transformers before the short circuit are known for sure, then the following equation 12b may be used instead of equation 12a.

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.

Then they contribute only to the initial symmetrical short-circuit current I: I,, is the rated current of the generator transferred to the high-voltage side see 4. Peak current based on method c: Calculated Values You can obtain the following values of short-circuit currents at the fault location for both maximum and minimum short circuit currents: Electrical equipment may be overstressed due to the short-circuit duration.

## IEC-60909 Short-Circuit in EasyPower

The comparison of ied is summarized below. The zero-sequence system impedance Z,, of the motor shall be given by the manufacturer, if needed see 4. In this case the Joule integral is determined from the characteristic of the current-limiting 60909. For simplification of the calculation, groups of motors including their connection cables may be combined to a single equivalent motor see motor M4 in figure 9. For simplification, it is permitted to use the same value for as for the three- phase short circuit.

An example for the introduction of the correction factors of equation 13 to the positive-sequence and the zero-sequence system impedances of the 600909-4 circuits is given in 2.

When a number of short circuits occur with a short time interval in between them, the resulting Joule integral is the sum of the Joule integrals of the individual short-circuit currents, as given in equation 1 Special methods to calculate i, with sufficient accuracy are given in 4.

All other static converters are disregarded for the short-circuit current calculation according to this standard.