IEC 60909 PDF
This calculation is based on IEC (, c), “Short-circuit currents in three-phase a.c. systems – Part 0: Calculation of currents” and. EasyPower offers a complete and accurate solution to short-circuit calculations in three-phase AC systems using the IEC standard. You can enter. IEC Edition INTERNATIONAL. STANDARD. NORME. INTERNATIONALE. Short-circuit currents in three-phase a.c. systems –.
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Short-circuit currents and short-circuit impedances may also be determined by system tests, by measurement on a network analyzer, or with a digital 6099.
This standard does not cover short-circuit currents deliberately created under controlled conditions short-circuit testing stations. The text of this standard is based on the following documents: The IEC collaborates closely with the International Organization for Standardization ISO in accordance with conditions determined by agreement between the two organizations.
As a result, reversible static converter-fed drives are treated for the calculation of short-circuit currents in a similar way as asynchronous motors. For the calculation of the partial short-circuit current I L 2 feeding into the short-circuit location F2, for example at the connection to the high-voltage side of the auxiliary transformer AT in figure 13, it 60099 sufficient to ie For phase currents, the maximum current of the three phases is used.
Figure 20 describes this situation with balanced and unbalanced short circuits with earth connection at the short-circuit location F.
Short Circuits in Power Systems: A Practical Guide to IEC 60909-0, 2nd Edition
If not, they are subject to additional considerations. At this date, the publication will be 0 reconfirmed; 0 withdrawn; 0 replaced by a revised edition, or 0 amended. This phenomenon is not dealt with in this standard.
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. Voltage sensitivity report for buses with voltage below threshold Transformer Phase Shift The short-circuit calculation provides the phase angle of the branch currents eic the bus voltages at various equipment.
The effective resistance per unit length RL of overhead lines at the conductor temperature 20 “C may be calculated from the nominal cross-section qn and the resistivity p: The short circuit rating is part of the data library. Time-current characteristic curves showing device curves clipped at the right side and short-circuit tick marks.
IEC-60909 Short-Circuit in EasyPower
For minimum short-circuit currents, the resistances are based on the estimated temperature at the end of the short-circuit condition. This figure is useful for information but should not be used instead of I isc.
The initial symmetrical current is calculated based on section 4. The following features are supported:. Using this method, the currents in each line conductor are found by superposing the currents of the three symmetrical component systems: You can view the currents in various formats such as phase currents for A, B and C phases or in symmetrical components: The equations 46 and 47 are given for the calculation of and in figure 3c: Short circuits may have one or more sources, as shown in figures 11, 12, and 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.
This postulates that the electrical equipment has a balanced structure, for example in the case of transposed overhead lines. This is the only active voltage of the network 1. These values cannot be used when calculating the aperiodic component id.
IEC Short-Circuit in EasyPower
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. Depending on the product f. Synchronous machines generators, motors, or compensators with terminal-fed static exciters do not contribute to I k in the case of a short-circuit at the terminals of the machine, but they contribute to l k if there is an impedance between the terminals and the short-circuit location.
EasyPower uses the following c factors as the default for maximum and minimum short-circuit conditions. For three-winding transformers with and without on-load iwc, three impedance correction factors can be found using the relative values of the reactances of the transformer see 3.
Calcul des courants Part O: For high voltage circuit breakers, the peak current is compared with the making capacity and the breaking current is compared with the rated breaking capacity.
Z S is the corrected impedance of a power station unit with LTC to the high-voltage side. No short-circuit current on the low-voltage or on the high-voltage side of the transformer in figure 20 is higher than the highest balanced or unbalanced short-circuit current in the case of an intact HV-feeding see figure The short-circuit impedances for electrical equipment are modified using impedance corrections factors that are calculated based on section 3.
Line-to-earth short-circuit currents for Initial symmetrical rms and peak Short-Circuit Duty Calculations EasyPower compares the short circuit results with protective device short-circuit ratings and displays the results in the text report and in the single line diagram.
Shift in current angle across delta-wye transformer Integration with Protective Device Coordination The IEC short-circuit results are integrated with the protective device coordination tools in EasyPower. For higher temperatures than 20 OC, see equation 3. Radial Network I tables, charts, graphs, figures For grounded systems the influence of motors on the line-to-earth short-circuit current cannot be neglected.
EasyPower calculates the Peak currents i p based on section 4.