IEC 60909-4 PDF
May 29, 2020 | by admin
Buy IEC/TR Ed. Short-circuit currents in three-phase a.c. systems Part 4: Examples for the calculation of short-circuit currents from SAI Global. The results meet requirements of IEC and match the example provided in IEC TR section 6. The IEC standard terminology is used in the user. The International Electrotechnical Commission (IEC) is the leading global IEC TR , Short-circuit currents in three-phase a.c. systems – Part 4.
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This postulates that the electrical equipment has a balanced structure, for example in the case of transposed overhead lines.
IEC TR 60909-4:2000
Log In Sign Up. In this standard it is calculated using a factor m for the time- dependent heat effect of the d. The text of this standard is based on the following documents: Figure 21 – Factor m for the heat effect of iwc d. Examples f o r the calculation of short-circuit currentsi The committee has decided that the contents of this publication will remain unchanged until Currents during two separate simultaneous single-phase line-to-earth short circuits and partial short-circuit currents following through earth IEC TR Xq Subtransient reactance of a synchronous machine saturated valuedirect axis respectively quadrature axis xd Unsaturated synchronous reactance, relative value xd sat Saturated synchronous reactance, relative value, reciprocal 660909-4 the saturated no-load short-circuit ratio Impedance, uec respectively relative value Short-circuit impedance of a three-phase a.
For the purpose of this standard, one has to make a distinction between short-circuit impedances at the short-circuit location F and the short-circuit impedances of individual electrical equipment.
Short-circuit duty results displayed in the single line drawing Table 5: The IEC short-circuit results are integrated with the protective device coordination tools in EasyPower. Electrical equipment may be overstressed due to the short-circuit duration.
IEC-60909 Short-Circuit in EasyPower
The initial symmetrical current is calculated based on section 4. They may be neglected. Short-circuit current of a near-to-generator short circuit with decaying a.
The impedances of the equipment in superimposed or subordinated networks are to be divided or multiplied by the square of the rated transformation ratio t.
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I tables, charts, graphs, figures You can view the currents in various formats such as phase currents for A, B and C phases or in symmetrical components: Highlighting of buses when voltage is below threshold Figure 7: NOTE The following values for resistivity may be used: Figure 2 – Short-circuit current of a near-to-generator short circuit with decaying a.
Figure 1 gives schematically the general course of the short-circuit current in the case of a far-fiom- generator short circuit. Skip to main content. 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. The effective resistance per 609909-4 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 values can be displayed in magnitude, magnitude and 60909- or in real and imaginary quantities.
Ikpis the steady-state short-circuit current of a generator at a three-phase terminal short-circuit. I 1 unacceptable, marketing specialist other This figure is useful iiec information but should not be used instead of I calculation. The zero-sequence short-circuit impedance at the short-circuit location F is obtained according to figure 5c, if an a. For the calculation of the initial short-circuit currents according to 4.
Symmetrical locked-rotor current of an asynchronous motor Rated current of electrical equipment Thermal equivalent short-circuit current d.
EasyPower provides the option of showing a warning when the short-circuit duty percent is above a user defined safety margin threshold but below the violation level.
Regardless of the time of short-circuit occurrence, the discharge current of the shunt capacitors may be neglected for the calculation of the peak short-circuit current. 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.
The impedance correction factor shall be applied also to the negative-sequence and the zero- sequence impedance of the transformer when calculating unbalanced short-circuit currents. This does not exclude the use of special methods, for example the superposition method, adjusted to particular circumstances, if they give at least the same precision.
EasyPower uses the following c factors as the default for maximum and minimum short-circuit conditions. Annex A forms an integral part of this standard.
The impedances and z o L of low-voltage and high-voltage cables depend on national techniques and standards and may be taken from IEC or from textbooks or manufacturer’s data. 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 initial short-circuit current at the short-circuit location F is the phasor sum of the individual partial short-circuit currents see figure Figure 16 can be used also for compound excited low-voltage generators with a minimum time delay tminnot greater than 0,1 s.
This fault is beyond the scope of, and is therefore not dealt with in, this standard. EasyPower calculates the Peak currents i p based on section 4.
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.
For remote buses and branches across transformers, a phase angle shift is applied accordingly by the short circuit calculations. Asymmetrical currents are calculated as the root mean square of the symmetrical and dc components. Then they contribute only to the initial symmetrical short-circuit current I: These remote currents and voltages are useful for relay setting. Definitions,principles and rules IEC 1: Three-phase short-circuit currents for breaking I b at0.