IEC 60909 1 PDF

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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Voltages and currents are to be converted by the rated transformation ratio t. 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. If underexcited operation of the power station unit is expected at some time for instance to a large extent especially in pumped storage plantsthen only when calculating unbalanced short- circuit currents with earth connection see figures 3c and 3d the application of Ks according to equation 22 may lead to results at the non-conservative side.

If synchronous motors have a voltage regulation, they are treated like synchronous generators. With these impedances 609909 corrected equivalent impedances LK, z B K and ZCKshall be calculated using the procedure given in equation i i.

For a synchronous generator use Rm see 3. Calculation of currents 1 General 1. I tables, charts, graphs, figures This part of IEC establishes a general, practicable and concise procedure leading to results, which are generally of acceptable accuracy. 609009 is not at all ci 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 impedances for the examples in figures 1l b and 1I C are given by the following equations: 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 6099 I,, I 0,Ol ICT3 holds.

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The 6090 of the short-circuit current calculation have an 11 accuracy also in the case of untransposed overhead lines. The object of the IEC is to promote international co-operation on all questions concerning standardization in the electrical and electronic fields.

For undated references, the latest edition of the normative document referred to applies.

Equations 84 and 85 are valid in the case of far-from-generator and in the case of near-to- generator short circuits. Within the accuracy of this standard, it is often sufficient to determine the short-circuit current at the short-circuit location F as being the sum of the absolute values of the individual partial short- circuit currents. When calculating unbalanced short-circuit currents in medium- or high-voltage systems and applying an 609909 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.

If not, they are subject to additional considerations. If only overexcited ifc is expected, then for the calculation of unbalanced short-circuit currents kec 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.

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Rated voltage, line-to-line r. If there are several transformers with slightly differing rated ifc ratios trT1trT The values of positive-sequence and negative-sequence impedances can differ from each other only in the case of rotating machines.

T k i and the factor K derived in 4. The need for the calculation of minimum short-circuit currents may arise because 69009 underexcited operation of generators low-load condition in cable systems or in systems including long overhead lines, hydro pumping stations.

Click here to sign up. Currents 06909 with equation 74 are larger than the real symmetrical short-circuit breaking. For three-winding transformers with and without on-load tap-changer, three impedance correction factors can be found using the relative values of the reactances of the transformer see 3.

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Systems at highest voltages of kV and above with long transmission lines need special consideration. The value should be obtained from the manufacturer. I In the case of minimum steady-state short circuits introduce c see 2. Calcul des courants Part O: I made the ieec choice ci I purchasing agent other This procedure is not allowed when calculating the peak short-circuit current i.