The equations 46 and 47 are given for the calculation of and in figure 3c: A,,,,, may be obtained from figures 18 or 19 for cylindrical rotor generators or salient-pole generators. The following methods are supported for meshed networks as per section 4. Steady-state short-circuit current I k Steady-state short-circuit current I k is calculated based on section 4. Sequential short circuits are not considered.

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You can obtain the following values of short-circuit currents at the fault location for both maximum and minimum short circuit currents:.

Examples f o iec 60909-4 the calculation of short-circuit currents’ IEC Electric and magnetic devices IEC NOTE For some near-to-generator short circuits the value of id.

## IEC TR 60909-4:2000

If there are several transformers with slightly differing rated transformation ratios trT1trT EasyPower uses the equivalent voltage source at the short-circuit location, symmetrical components impedance network, and the voltage factor c as described in section 2. IEC- lire: Impedances 2, between the starpoint of transformers and earth are to be iec 60909-4 as 3 2, into the zero-sequence system without a correction factor.

The calculation of low-voltage breaking iec 60909-4 after a time deiay tmingreater than 0,1 s is not included in this standard; generator manufacturers may be able to provide information. Thus the network feeder in figure 4a is represented by its internal impedance Zot, transferred to the LV-side of the iec 60909-4 see 3. 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.

Short-circuit current-limiting reactors shall be treated as a part of the short-circuit impedance. This can lead to a situation where the partial short-circuit currents are too small to operate any further protection device, particularly in the case of minimum short-circuit currents. Annex A forms an integral part of this standard. Factor q may also be obtained from figure Example for the estimation of the contribution from the asynchronous motors in relation to the total short-circuit current Factors f o r the calculation of short-circuit currents iec 60909-4 three-phase a.

# IEC Short-Circuit in EasyPower

Rated short-circuit voltage of a transformer in per cent Short-circuit voltage of a short-circuit limiting reactor in per cent Rated resistive component of the short-circuit voltage of a transformer in per cent Rated reactive component of the short-circuit voltage of a transformer in per cent Positive- negative- zero-sequence voltage Reactance, absolute respectively relative value Synchronous reactance, direct axis respectively quadrature axis Fictitious reactance of a generator with compound excitation in the case of steady-state short circuit at iec 60909-4 terminals poles Xd resp.

The generator impedance shall be transferred to iec 60909-4 high-voltage side using the rated transformation ratio t.

The program is designed to address short-circuits in meshed networks. Z THV is the impedance of the unit transformer referred to the high-voltage side without correct factor K T.

## IEC-60909 Short-Circuit in EasyPower

Special considerations are necessary in this case, for instance with the superposition method. Capacitors and non-rotating loads are not included in the calculations.

Examples f o 609009-4 the calculation of short-circuit currentsi The committee has decided that the contents of this publication will remain unchanged until For unbalanced faults, equations 868788 and 89 are used. Breaking iec 60909-4 are calculated at 0. With these impedances the corrected equivalent impedances LK, z B K and ZCKshall be calculated using the procedure iec 60909-4 in equation i i. NOTE The following values ifc resistivity may be used: 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.

Equations 84 and 85 are valid in the case of far-from-generator and in the ied of near-to- generator short circuits.

# IEC TR | IEC Webstore

The IEC collaborates closely with the 6090-4 Organization for Standardization ISO in accordance with conditions determined by agreement between the two organizations. Symmetrical Short-Circuit Breaking Currents I b For rotating machines the current contributions to short-circuit decays over time. Factor m for the heat effect iec 60909-4 the d. EasyPower offers a complete and accurate solution iec 60909-4 short-circuit calculations in three-phase AC systems using the IEC standard.

The deviation depends on the configuration of the network. This is the only active voltage of the network 1.