IEC Short-Circuit Current Calculation in Three-Phase A.C. Systems Part 1: Factors for the Calculation of Short-Circuit Currents in Three-Phase A.C. Part 1: Factors for the calculation of short-circuit currents according to IEC 0. Numéro de référence. Reference number. CEI/IEC/TR The International Electrotechnical Commission (IEC) is the leading global IEC TR , Short-circuit currents in three-phase a.c. systems – Part 1: .

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A,,, may be obtained from figures jec or 19 for cylindrical rotor generators or salient-pole generators. The influence of various winding-temperatures on RGf is not considered.

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The factor p may also be obtained from figure In a near-to-generator short circuit, the short-circuit current behaves generally as shown in figure 2. The impedance of the auxiliary transformer AT in figure 13 is to be corrected with KT from 3. 609009 IEC collaborates closely with the International Organization for Standardization ISO in accordance with conditions determined by agreement between the two organizations.

This part of IEC establishes a general, practicable and concise 6099 leading to results, which are generally of acceptable accuracy. IEC TR2- lire: RL is the line resistance for a conductor temperature of 20 OC, when calculating the maximum short-circuit currents.

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Q5 This standard meets my needs: Except for special cases, the zero-sequence short-circuit impedances at the short-circuit location differ from the positive-sequence and negative-sequence short-circuit impedances. The value should be obtained from the manufacturer.

Figure 16 can be used also for compound excited low-voltage generators with a minimum time delay tminnot greater than 0,1 s. The deviation depends on the configuration of the network. For dated references, subsequent amendments to, or revisions of, any of these publications do not apply.

Electrical equipment may be overstressed due to the short-circuit duration.

The peak short-circuit current i, at a short-circuit location F, fed from sources which are not meshed with one another, in accordance with figure 12, is the sum of the partial short-circuit currents: In general, the calculation according to 4.

I quality of writing Transformer secondary short circuits. NOTE The current in a three-phase short circuit is assumed to be made simultaneously in all poles. isc

The values are given in table 1 NOTE The introduction of a voltage factor c is necessary ic various reasons. IkP Steady-state short-circuit current at the terminals poles of a generator with compound excitation Initial symmetrical short-circuit current r.

Special considerations are necessary in this case, for instance with the superposition method.

Factor p for calculation of short-circuit breaking current 1, This part of IEC does not deal with the calculation of short-circuit currents in installations on board ships and aeroplanes. If only overexcited operation is expected, then for the calculation of unbalanced short-circuit currents the correction factor Ks from equation 22 shall be used for both the positive-sequence and the negative-sequence system impedances of the power station unit.

As a result, reversible static converter-fed drives are treated for the calculation of short-circuit currents in a similar way as asynchronous motors. Impedances 2, between the starpoint of transformers and earth are to be introduced as 3 iex, into the zero-sequence system without a correction factor.

iex

In this case, the three-fold zero-sequence current flows through the joint return. Examples f o r the calculation of short-circuit currents’ IEC Sequential short circuits are not considered.

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Characterization of short circuits and their currents The three impedance correction factors given in equation 13 shall be introduced also to the negative-sequence and to the zero-sequence systems of the three-winding transformer.

Additional information may be found in IEC The effective resistance of the stator of synchronous machines lies generally much below the given values for RGf.

The initial symmetrical short-circuit currents riQ,, and riQm, on the high-voltage side of the trans- former shall be given by the supply company or by an adequate calculation according iex this standard. Linand il,, factors for cylindrical rotor generators When calculating the partial short-circuit current I: NOTE For some near-to-generator short circuits the ieec of id.

In all cases I L is equal to Ikv,because the short circuits are far-from-generator short circuits see 1.

This is possible if the d. At this date, the publication will be 0 reconfirmed; 0 withdrawn; 0 replaced by a revised edition, or 0 ice. For two-winding transformers with and without on-load tap-changer, an impedance correction factor KT is to be introduced in addition to the impedance evaluated according to equations 7 to 9: