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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 effective resistance per unit length RL of overhead lines at the conductor temperature 20 “C may be calculated from the nominal cross-section qn and the resistivity p: The synchronous generator impedance correction factor K G for generators without unit transformers is calculated as follows per section 3.

The short circuit rating is part of the data library. The value should be obtained from the manufacturer.

Systems at highest voltages of kV and above with long transmission lines need special consideration. Shunt admittances for example, line capacitances and passive loads are not to be considered when calculating short-circuit currents in accordance with figure 4b. T JSrT ; t, is the rated transformation ratio of the unit transformer: Factors ;Iminand il,,for salient-pole circcuit 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 The upstream circuit breakers do not trip instantaneously whereas the most downstream circuit breaker trips fast, enabling shor coordination.


Symmetrical Short-Circuit Breaking Currents I b For rotating machines the current contributions to short-circuit decays over time.

For a short circuit at the busbar B in figure 9, the partial short-circuit current of the low-voltage motor group M4 may be neglected, if the condition I,, I 0,Ol ICT3 holds.

06909 For high voltage circuit breakers, the peak current is compared with the making capacity and the breaking current is compared with the rated breaking capacity.

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.

IEC- lire: Three-phase short-circuit currents for breaking I b at0. The calculation of the minimum steady-state short-circuit current in the case of a near-to- generator short circuit, fed by one or’ several similar and parallel working generators with compound excitation, is made as follows: For the short-circuit impedance of synchronous generators in the zero-sequence system, the following applies with KG from equation 1 8: CE1 TR2– Instead of: In the case of unbalanced short circuits, the impedance correction factor KSOfrom equation 24 shall be applied to circuiit the positive-sequence and the negative-sequence system impedances of the power station unit.

Calcul des courants Part O: Example for the estimation of the contribution from the asynchronous motors in relation to the total short-circuit calculagion Short circuits may have one or more sources, as shown in figures 11, 12, and The influence of various winding-temperatures on RGf is not considered.

IEC Short-Circuit in EasyPower

Factor p for calculation of short-circuit breaking current 1, Xq Subtransient reactance of a synchronous machine saturated valuedirect axis respectively quadrature axis xd Unsaturated synchronous reactance, relative value xd sat Saturated synchronous reactance, relative value, reciprocal calculatin the saturated no-load short-circuit ratio Impedance, absolute respectively relative value Short-circuit impedance of a three-phase a.


Factor m for the heat effect of the d.

This is admissible, because the impedance correction factor KTfor network transformers is introduced. Short-circuit equipment duty report Voltage Sensitivity Analysis Short-circuit on any bus results in voltage drop in other near buses in the system.

IEC-60909 Short-Circuit in EasyPower

Then they contribute only to the initial symmetrical short-circuit current I: The factors m and n first appeared as Figures 12a and 12b of IEC and are identical to them. 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 For minimum short-circuit calculations the motor contribution is excluded.

The IEC standard terminology is used in the user interface and reports. Switches use the peak current to compare with making capacity. Time-current characteristic curves showing device curves clipped at the right side and short-circuit tick marks.

Short-circuit duty results displayed in the single line drawing Table 5: The short-circuit calculation provides the phase angle of the branch currents and the bus voltages at various equipment.