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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The transformer correction factor K T for two winding units with 660909-4 without on-load tap changer LTC is calculated as follows per section 3. Voltage sensitivity report for buses with voltage below threshold Transformer Phase Shift The short-circuit calculation provides the phase angle of the branch currents and the bus voltages at various equipment.

O 1 marks the positive-sequence neutral reference.

The EasyPower library is populated with data for circuit breakers, fuses and switches. In some special cases, it could happen that the decaying short-circuit current reaches zero for the first time, some cycles after the short circuit took place.

As per section 4. In a system of low voltage breakers with ZSI, when the current through any circuit breaker exceeds the short time pickup ieec restraining signal is sent to upstream circuit breakers. CE1- Instead of: When an impedance is present between the starpoint of the generator and earth, the correction factor KG shall not be applied to this impedance.

Earth ground trip functions for low voltage circuit breakers or relays use the symmetrical earth ground current. Eic do not contribute to the symmetrical short-circuit breaking current I, and the steady-state short-circuit current I k.

## IEC-60909 Short-Circuit in EasyPower

For the short-circuit impedance of synchronous generators in the zero-sequence system, the following applies with KG from equation 1 8: Electrical equipment may be overstressed due to the short-circuit duration. The short-circuit calculation provides the phase angle of the branch currents and the bus voltages at various equipment.

In this case, the symmetrical short- circuit breaking current Ib is smaller than the initial symmetrical short-circuit current I,”. Definitions,principles and rules IEC 1: In the case of a near-to-generator short circuit, the short-circuit current can be considered as the sum of the following two components: Any branch may be a series combination of several impedances.

The deviation depends on the configuration of the network. This part of IEC establishes a general, practicable and concise procedure leading to results, which are generally of acceptable accuracy. For TCC clipping you can choose one from initial, breaking and steady state currents.

The following methods are supported for meshed networks as per section 4. 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.

The values can be displayed in magnitude, magnitude and angle, or in real and imaginary quantities.

### IEC Short-Circuit in EasyPower

Currents calculated with equation 74 are larger than the real symmetrical short-circuit breaking. In this case, it is necessary to distinguish between networks ief and without parallel branches see 4.

The IEC shall not be held responsible for identifying any or all such patent rights. If there are several transformers with slightly differing rated transformation ratios trT1trT I cochez tout ce qui convient Je suis lehn: In the case of high-voltage feeders with nominal voltages above 35 irc fed by overhead lines, the equivalent impedance 2, may in many cases be considered as a reactance, i.

I quality of writing As a result, reversible static converter-fed drives are treated for the calculation of short-circuit currents in a similar way as asynchronous 6090-94. For 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.

These values cannot be used when calculating the aperiodic component id. The symbols represent physical quantities possessing both numerical values and dimensions that are independent of units, provided a consistent unit system is chosen, for example the international 6090-94 of units SI. In all cases it is possible to determine the short-circuit current at the short-circuit location F with the help of an equivalent voltage source.

## IEC TR 60909-4:2000

For rotating machines the current contributions to short-circuit decays over time. 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.

NOTE Equivalent circuits of the positive-sequence and the zero-sequence system are given in IECtable Iitem 4 to 7 for different cases of starpoint earthing. Calcul des courants Part O: For simplification, it is permitted to use the same value for as for the three- phase short circuit.

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 jec sufficient to take: