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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The generator impedance shall be transferred to the high-voltage side using the rated transformation ratio t. IEC standard specifies clock number notation and their respective phase angle shift for transformers.

The upstream circuit breakers do not trip instantaneously whereas the most downstream circuit breaker trips fast, enabling selective coordination.

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 transformer correction factor K T for two winding units with or without on-load tap changer LTC is calculated as follows per section 3.

Figure 1 – Short-circuit current of a far-from-generator short circuit with constant a. Log In Sign Up.

### IEC Short-Circuit in EasyPower

The correction factor Kso shall also be applied to the zero-sequence system impedance of the power station unit excepting, if present, an impedance component between the star point of the transformer and earth. Impedances between a starpoint and earth shall be introduced without correction factor. 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 hsort section 3.

For phase TCC clipping and tick marks, EasyPower automatically selects the asymmetrical currents for low voltage circuit breakers, fuses and electromechanical relays. Steady-state short-circuit current I k Steady-state short-circuit current I k is calculated based on section 4. In this case special considerations beyond the scope and procedure given in this standard have to be taken into account see for instance 2.

The correction factors for three-winding transformers with or without LTC are calculated using the following shortt. In this case, the symmetrical short- circuit breaking current Ib ckrcuit smaller than the initial symmetrical short-circuit current I,”.

## IEC-60909 Short-Circuit in EasyPower

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.

These values cannot be used when calculating the aperiodic component id.

For transformers with delta and start wye winding connections, the clock notations 1,3,5,7,9 and ciruit are supported in the database. I,, is the rated current of the generator transferred to the high-voltage side see 4. The values are given in table 1 NOTE The introduction of a voltage factor c is necessary for various reasons. Switches use the peak current to compare with making capacity. The factor K shali be calculated according to 4.

Factor n for the heat effect of the a. In general, the calculation according to 4. The three impedance correction factors given in equation 13 shall be introduced also to the negative-sequence and xalculation the zero-sequence systems of the three-winding transformer. For increased accuracy, equations 79, 76and 77 can be used. Voltage sensitivity report for buses with voltage below threshold Transformer Phase Shift The short-circuit calculation provides the phase angle of the branch currents and the bus voltages at various equipment.

This procedure is not allowed when calculating the peak short-circuit current i.

Calcul des courants Short-circuit currents in three-phase a. The resistance is to be considered if the peak short-circuit current ip or the d. Calculated Values You can obtain the following calcullation of short-circuit currents at the fault location for both maximum and minimum short circuit currents: Peak current based on method b: The calculation cricuit the three-phase peak short-circuit current i, applies to the line conductor and to the instant at which the greatest possible short-circuit current exists.

Synchronous Generator Impedance Correction Factor The synchronous generator impedance correction factor K G for generators without unit transformers is calculated as follows per sohrt 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 The short-circuit calculation calculatuon the phase angle of the branch currents and the bus voltages at various equipment.

The IEC shall not be held responsible for identifying any calculafion all such patent rights. With respect to equation 99 in table 3 the steady-state short-circuit current of asynchronous motors is zero in the case of a three-phase short circuit at the terminals figure 12 and equation Short-circuit on any bus results in voltage drop in other near buses in the system.

When calculating unbalanced short-circuit currents in medium- or high-voltage systems and applying an equivalent voltage source at the short-circuit location, the zero-sequence capacitances of lines and the zero-sequence shunt admittances are to be considered for isolated. All other static converters are disregarded for the short-circuit current calculation according to this standard. CE1 TR2– Instead of: The implementation is as per sections 4. For dated references, subsequent amendments to, or revisions of, any of these publications do not apply.

Calculations are simplest for balanced short circuits on radial systems, as the individual contributions to a balanced short circuit can be evaluated separately for each source figures 12 or The superposition method gives the short-circuit current related to the one load flow presupposed.