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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Short-circuit equipment duty report Voltage Sensitivity Analysis Short-circuit on any bus results in voltage drop in other near buses in the system. The factor K shali be calculated according to 4. For 60909-44, it is permitted to use the same value of Kas for the three-phase short circuit.

The program is designed to address short-circuits in meshed networks. In this standard it is calculated oec a factor m for the time- dependent heat effect of the d.

Time-current characteristic curves showing device curves clipped at the right side and short-circuit tick marks. Short-circuit currents and short-circuit impedances may also be determined by system tests, by measurement on a network analyzer, or with a digital computer. Single-fed short circuits supplied by a transformer according to figure 4, may a priori be regarded as far- from-generator short circuits if X, 2 Ur, with XQ, calculated in accordance with 3.

Asymmetrical values can be used with protective devices that respond to the asymmetrical currents. As per section 4. This correction factor shall not be introduced for unit transformers of power station units see 3.

It is not necessary for the product 1, Examples f o r the calculation of short-circuit currentsi The committee has decided that the contents of this publication will remain unchanged until In this case, the symmetrical short- circuit breaking current Ib is smaller than the initial symmetrical short-circuit current I,”. This will display the curve only up to the maximum current the device will see. Ratings for HV breaker in project file loaded from the library In the equipment short-circuit duty report, comments and text colors provide indication of problem areas.

In a near-to-generator short circuit, the short-circuit current behaves generally as shown in figure 2. Electric and magnetic devices IEC You can display short-circuit tick marks for initial, breaking and steady state currents. 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.

Ik Steady-state short-circuit current r. In general, two short-circuit currents, which differ in their magnitude, are to be calculated: Electric and magnetic circuits IEC 15 1: EasyPower offers a complete and accurate solution to short-circuit calculations in three-phase AC systems using the IEC standard.

This is the only active voltage of the network 1. If the short circuit is a far-from-motor short circuit i.

U, is the nominal voltage of the system; ur, is the rated voltage of the generator; ZGK is the corrected subtransient impedance of the generator; 2, is the subtransient impedance of the generator in the positive-sequence system: I cochez tout ce qui convient Je suis lehn: Fuses and low voltage circuit breakers ratings are compared with initial currents. I In the case of minimum steady-state short circuits introduce c see 2.

As a result, reversible static converter-fed drives are treated for the calculation of short-circuit currents in a similar way as asynchronous motors.

### IEC Short-Circuit in EasyPower

Short-circuit current-limiting reactors shall be treated as a part of the short-circuit impedance. The correction factor Kso shall also be applied to the zero-sequence system impedance of the 609909-4 station unit excepting, if present, an impedance component between the star point of the transformer and earth.

They do not contribute to the symmetrical short-circuit breaking current I, and the steady-state short-circuit current I k. This factor is also used in calculating impedance correction lec.

## IEC TR 60909-4:2000

For phase currents, the maximum current of the three phases is used. RL is the line resistance for a conductor temperature of 20 OC, when calculating the maximum short-circuit currents.

I certification technical documentation ci ci The influence of various winding-temperatures on RGf is not considered. The impedance ZrS1in equation 38 or 43 is used to determine the partial short-circuit current ILT in figure 13 for the short circuit in F3. Xk may be neglected. Despite these assumptions being not strictly true for the power systems considered, the result of the calculation does fulfil the objective to give results which are generally of acceptable accuracy.

If only overexcited operation is expected, then for the calculation of unbalanced short-circuit currents the 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.

For this calculation method, an equivalent voltage 6099-4 at the short-circuit location is introduced.