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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For breaking current you can choose from 0. 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-60909 Short-Circuit in EasyPower

If the long-term operating conditions of network transformers before the oec circuit are known for sure, then the following equation 12b may be used instead of equation 12a. The need for the calculation of minimum short-circuit currents may arise because of underexcited operation of generators low-load condition 60909- cable systems or in systems including long overhead lines, hydro pumping stations.

I k autre s In general, the calculation according to 4. 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.

## IEC TR 60909-4:2000

Transformer Impedance Correction Factors The transformer correction factor K T for two winding units with or without on-load tap changer LTC is calculated as follows per section 3. I In the case of minimum steady-state short circuits introduce c see 2. Thus the network feeder in figure 4a is represented by its internal impedance Zot, transferred to the LV-side of the transformer see 3. Examples f o r the calculation of short-circuit currentsi The committee has decided that the contents of this publication will remain unchanged until Short circuits 6090-94 have one or more sources, as shown in figures 11, 12, and Synchronous machines generators, motors, or compensators with terminal-fed static exciters do not contribute to I k in the case iev a short-circuit at the terminals of the machine, but they contribute to l k if there is an impedance between the terminals and the short-circuit location.

This standard does not cover short-circuit currents deliberately created under controlled conditions short-circuit testing stations. Shunt admittances for example, line capacitances and passive loads are not to be considered when calculating short-circuit currents in accordance with figure 4b. The IEC short-circuit results are integrated with the protective device coordination tools in EasyPower.

### IEC TR | IEC Webstore

In this case, the symmetrical iev circuit breaking current Ib is smaller than the initial symmetrical short-circuit current I,”. Impedances between a starpoint and earth shall be introduced without correction factor. Steady-state short-circuit current I k Steady-state short-circuit current I k is calculated based on section 4. EasyPower uses the following c factors as the default for maximum and minimum short-circuit conditions. This first edition cancels and replaces IEC published in and constitutes a technical revision.

### IEC Short-Circuit in EasyPower

IEC TR2- lire: For remote buses and branches across transformers, a phase angle shift is applied accordingly by the short uec calculations. Earth ground trip functions for low voltage circuit breakers or relays use the symmetrical earth ground current.

For the effective reactance of the generators, introduce: O 1 marks the positive-sequence neutral reference. While using fuses or current-limiting circuit-breakers to protect substations, the initial 6009-4 short- circuit current is first calculated as if these devices were not available. Additional information may uec found in IEC The values can be displayed in magnitude, magnitude and angle, or in real and imaginary quantities. For the calculation of the partial short-circuit current I L 2 feeding into the short-circuit location F2, for example at the connection to the high-voltage side of the auxiliary transformer AT in figure 13, it is sufficient to take: The equivalent voltage source is the only active voltage of ice system.

Phasor diagram of a synchronous generator at rated conditions For the short-circuit impedance of synchronous generators in the zero-sequence system, the following applies with KG from equation 1 8: 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.

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. In general, two short-circuit currents, which differ in their magnitude, are to be calculated: Medium-voltage motors have to be considered in the calculation of maximum short-circuit current see 2.

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.

Depending on the product f. In the case of high-voltage direct-current transmission systems, the capacitor banks and filters need special considerations, when calculating a. Remember me on this computer. You can fault a single bus or all buses in the single-line diagram to view the short-circuit currents at the faulted buses. The initial line-to-earth short-circuit current Iil in figure 3d shall be calculated by: Short-circuit currents decaying ieec time Methodology EasyPower kec the equivalent voltage source at the short-circuit location, symmetrical components impedance network, and the voltage factor c as described in section 2.

No short-circuit current on the low-voltage or on the high-voltage side of the transformer in figure 20 is higher than the highest balanced or unbalanced short-circuit current in the case of an intact HV-feeding see figure The 60099-4 of positive-sequence and negative-sequence impedances can differ from each other only 609099-4 the case of rotating machines. This postulates that the electrical equipment has a balanced structure, for example in the case of transposed overhead lines.

In the equipment short-circuit duty report, comments and text colors provide indication of problem areas.