If the highest partial short-circuit current of the power station unit at the high-voltage side of the unit transformer with off-load taps is searched for, choose l-pT. For this calculation method, an equivalent voltage source at the short-circuit location is introduced. For dated references, subsequent amendments to, or revisions of, any of these publications do not apply.įor 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. Steady-state short-circuit current I k Steady-state short-circuit current I k is calculated based on section 4. I k autre s You can enter equipment data and parameters via user friendly interface.
When an impedance is present between the starpoint of the generator and earth, the correction factor KG shall not be applied to this impedance.
Transformer Impedance Correction Factors The transformer correction factor K T for two winding units with or without on-load tap changer LTC is calculated as follows per section 3.ĬE1 TR2– Instead of: In existing low-voltage systems it is possible to determine the short-circuit impedance on the basis of measurements at the location of the prospective short circuit considered. IEC Short-Circuit in EasyPowerįor 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. Special considerations are necessary in this case, for instance with the superposition method.
The calculation of low-voltage breaking currents after a time deiay tmingreater than 0,1 s is not included in this standard generator manufacturers iev be able to provide information.ĭIETA MICHEL MONTIGNAC ESPECIAL MUJER PDF This book is a practitioner’s guide intended for students, electrical engineers, engineers in power technology, the electrotechnical industry, engineering consultants, energy suppliers, chemical engineers and physicists in industry. Asymmetrical currents are calculated as the root mean square of the symmetrical and dc components. Examples f o r the calculation of short-circuit currentsi The committee has decided that the contents of this publication will remain unchanged until Subtransient impedances are used for rotating machines with the impedance correction factors.Įarth 60099 trip functions for low voltage circuit breakers or relays use the symmetrical earth ground current. IEC-60909 Short-Circuit in EasyPowerĪutomatic Disconnection for eic TN System 56 6. The values of p in equation 70 apply if synchronous machines are excited by rotating exciters or by static converter exciters provided, for static exciters, the minimum time delay tminis less than 0,25 s and the maximum excitation voltage is less than 1,6 times rated load excitation-voltage. Switches use the peak current to compare with making capacity. Connection Box to Service Panel The type of short circuit which leads to the highest short-circuit current depends on the values of the positive-sequence, negative-sequence, and zero-sequence short-circuit impedances of the system. With 6009 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 For two-winding transformers with and without 609099 tap-changer, an impedance correction factor KT is to be introduced in addition to the impedance evaluated according to equations 7 to 9: I In jec case of minimum steady-state short circuits introduce c see 2.įor minimum short-circuit calculations the motor contribution is excluded. The calculation of the three-phase peak short-circuit current i, applies to the line conductor and to the instant at which the greatest possible short-circuit current exists. Short-circuit currents in three-phase a.c.
EasyPower offers a complete and accurate solution to short-circuit calculations in three-phase AC systems using the IEC standard.
systems – Part 0: Calculation of currents” and. This calculation is based on IEC (, c), “Short-circuit currents in three-phase a.c.