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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Ice m for the heat effect of the d. Operational data and the load of consumers, tap- changer position of transformers, excitation of generators, and so on, are dispensable; additional calculations about all the different possible load flows at the moment of short circuit are superfluous.

If the Joule integral or the thermal equivalent short-circuit current shall be calculated for unbalanced short circuits, replace I: While using fuses or current-limiting circuit-breakers to protect substations, the initial symmetrical short- circuit current is first calculated as 609099 these devices were not available.

Normally, the steady-state short-circuit current Jec is smaller than the symmetrical short-circuit breaking current 1. In the case of high-voltage feeders with nominal voltages above 35 kV fed by overhead lines, the equivalent impedance 2, may in many cases be considered as a reactance, i.

Medium-voltage motors have to be considered in the calculation of maximum short-circuit current see 2. The factor p may also be obtained from figure The initial symmetrical short-circuit currents riQ,, and riQm, irc the high-voltage side of the trans- former shall be given by the supply company or by an adequate calculation according to this standard.

The factors m and n first appeared as Figures 12a and 12b of IEC and are identical to them. 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.

For the calculation of the initial short-circuit currents according to 4. Calcul des courants Short-circuit currents in three-phase a. I k autre s The values are given in table 1 NOTE The introduction of a voltage factor c is necessary for various reasons.

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This first edition cancels and replaces IEC published in and constitutes a technical 6099. I librarian researcher I design engineer safety engineer ci Q7 Please assess the standard in the I following categories, using testing engineer ci the numbers: 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. For the short-circuit impedances of synchronous generators in the negative-sequence system, the following applies with KG from equation 1 8: A contribution is also given if, in case of a power station unit, the short-circuit occurs on the high-voltage side of the unit transformer see figure 1lc.

Depending on the product f. ifc

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It is assumed that the operating voltage at the terminals of the generator is equal to UrG. In some special cases, it could happen that the decaying short-circuit current reaches zero for the first time, some cycles after the short circuit took place. From the calculated initial symmetrical short-circuit current and characteristic curves of the fuses or current-limiting circuit- breakers, the cut-off current is determined, which is the peak short-circuit current of the downstream substation.

For the effective reactance of the generators, introduce: Log In Sign Up.

Calculation 6009 currents 1 General 1. In the case of figure 4, for instance, to the LV side. ILR highest symmetrical r. That is why it is not possible to give an easy method of calculating i, and id.

In general, the calculation according to 4. If Si is used in spite of this in connection with short-circuit calculations, for instance to calculate the internal impedance of a network feeder at the connection point Q, then the definition given should be used in the following form: The calculation of low-voltage breaking currents after a time deiay tmingreater than 0,1 s is not included in this standard; generator manufacturers may ief able to provide information.

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 iiec machines are replaced by their internal impedances.

The object of the IEC is to promote international co-operation on all questions concerning standardization in the electrical and electronic fields. The impedances in systems connected through transformers to the system, in which the short circuit occurs, have to be transferred by the square of the rated transformation ratio.

If there are several transformers with slightly differing rated transformation ratios trT1trT It does not take into account adjustable time delays of tripping devices. The decaying aperiodic component id. Definitions,principles and rules IEC 1: For simplification, it is permitted to use the same value of Kas for the three-phase short circuit. Figure 16 can be used also for compound excited low-voltage generators with a minimum time delay tminnot greater than 0,1 s.

Shunt admittances for example, line capacitances and passive loads are not to be considered when calculating short-circuit currents in accordance with figure 4b. Currents calculated with equation 74 are larger than the real symmetrical short-circuit breaking.