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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## IEC-60909 Short-Circuit in EasyPower

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. Symmetrical Short-Circuit Breaking Currents I b For rotating machines the current contributions to short-circuit decays over time. Peak current based on method c: Electric and magnetic devices IEC This part of IEC does not deal with the calculation of short-circuit currents in installations on board ships and aeroplanes.

Systems at highest voltages of kV and above with long transmission lines need special consideration. I In the case of minimum steady-state short circuits introduce c see 2. View of the single line diagram in the time current characteristics TCC plot for protective devices.

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. 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.

An example for the introduction of the correction factors of equation 13 to the positive-sequence and the zero-sequence system impedances of the equivalent circuits is given in 2. Currents during two separate simultaneous single-phase line-to-earth short circuits and partial short-circuit currents following through earth IEC TR 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: Examples f o r the calculation of short-circuit currents’ IEC O 1 marks the positive-sequence neutral reference.

This method, therefore, does not necessarily lead to the maximum short-circuit current.

### IEC Short-Circuit in EasyPower

The IEC standard terminology is used in the user interface and falculation. Phasor diagram of a synchronous generator at rated conditions Factor q may also be obtained from figure You can also view the remote branch currents and remote bus voltages. Symmetrical currents are applied for relays with DC offset filter. Any divergence between the IEC Standard and the corresponding national or regional standard shall be clearly indicated in the latter.

Their preparation is entrusted to technical committees; any IEC National Committee interested in the subject dealt with may participate in this preparatory work.

Calcul des courants Part O: EasyPower applies impedance correction factors in short circuit calculation based on IEC standard. The IEC short-circuit results ieec integrated with the protective device coordination tools in EasyPower.

In this case special considerations beyond the scope and procedure given in this standard have to be taken into account see for instance 2.

For phase TCC clipping and tick marks, EasyPower automatically selects the asymmetrical currents for low voltage circuit breakers, fuses and electromechanical relays. 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. 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.

In the equipment vircuit duty report, comments and text colors provide indication of problem areas. Figure 16 can be used also for compound excited low-voltage generators with a minimum time delay tminnot greater than 0,1 s. If synchronous motors have a voltage regulation, they are treated like synchronous generators.

The synchronous generator impedance correction factor K G for generators without unit transformers is calculated as follows per section 3.

In this case, the three-fold zero-sequence 60099 flows through the joint return.

The need for the calculation of minimum short-circuit currents may arise because of underexcited operation of generators low-load condition in cable systems or in systems including long overhead lines, hydro pumping stations. Ratings for HV breaker in project file loaded from the library In the equipment short-circuit duty calculatoin, comments syort text colors provide indication of problem areas.

Calculation of currents 1 General 1. The following types of unbalanced short circuits are treated in this standard: I tables, charts, 60099, figures For grounded systems the influence of motors on the line-to-earth short-circuit current cannot be neglected. All other static converters are disregarded for the short-circuit current calculation according to this standard.

If the Joule integral or the thermal equivalent short-circuit current shall be calculated for unbalanced short circuits, replace I: The impedance of the network feeder and the transformer are related to the LV-side and the last one is also corrected with KT calculaation 3. For dated references, subsequent amendments to, or revisions of, any of these publications do not apply.

The resistance is to be considered if the peak short-circuit current ip or the d. This is the only active voltage of the network 1. That is why it is not possible to give an easy method of calculating i, and id.