Download Citation on ResearchGate | Applying IEC , Fault Current Calculations | Rather than the short-circuit current that would occur in a specific. Applying IEC , short-circuit current calculations. Abstract: Rather than the short-circuit current that would occur in a specific instance, IEC derives. The initial short circuit current for a is as per IEC Equation

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The upstream circuit breakers do not trip instantaneously whereas the most downstream circuit breaker trips fast, enabling selective coordination.

In special cases the zero-sequence equivalent short-circuit impedance of network feeders may need to be considered, depending on the winding configuration and the starpoint earthing of the transformer.

Steady-state short-circuit current I k Steady-state short-circuit current I k is calculated based on section 4. The three impedance correction factors given in equation 13 shall be introduced also to the negative-sequence and to the zero-sequence systems of the three-winding transformer.

Z S is the corrected impedance of a power station unit with LTC to the high-voltage side. For higher temperatures than 20 OC, see equation 3. Electric and magnetic devices IEC Each branch short- circuit current can be calculated as an independent single-source three-phase short-circuit current in accordance with equation 29 and the information given in 4.

The voltage factor c is used to scale the equivalent voltage source in the calculations to account for variations in the system voltage. Click here to sign up. I cochez tout ce qui convient Je suis lehn: As described in the methodology the solution is obtained using the equivalent voltage source at the short-circuit location, symmetrical components impedance network, and the voltage factor c.

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.

Currents during two separate simultaneous single-phase line-to-earth short circuits and partial short-circuit currents following through earth IEC TR Rated short-circuit voltage of a transformer in per cent Short-circuit voltage of a short-circuit limiting reactor in per cent Rated resistive component of the short-circuit voltage of a transformer in per cent Rated reactive component of the short-circuit voltage of a transformer in per cent Positive- negative- zero-sequence voltage Reactance, absolute respectively relative value Synchronous reactance, direct axis respectively quadrature axis Fictitious reactance of a generator with compound excitation in the case of steady-state short circuit at the terminals poles Xd resp.

Three-phase short-circuit currents for breaking I b at0.

For a synchronous generator use Rm see 3. Definitions,principles and rules IEC 1: Example for 6099 estimation of the contribution from the asynchronous motors in relation to the total short-circuit current 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.

### IEC Short-Circuit in EasyPower

Enter the email address you signed up with and we’ll email you a reset link. Figure 1 gives schematically the general course of the short-circuit current in the case of a far-fiom- generator short circuit. In a near-to-generator short circuit, the short-circuit current behaves generally as shown in figure 2. 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.

You can view the currents in various formats such as phase currents for A, B and C phases or in symmetrical components: Special methods to calculate i, with sufficient accuracy are given in 4. They do not contribute to the symmetrical short-circuit syort current I, and the steady-state short-circuit current I k. You can display short-circuit tick marks for initial, breaking and steady state currents.

If the Joule integral or the thermal equivalent short-circuit current shall be calculated for unbalanced short circuits, replace I: Phasor diagram circut a synchronous generator at rated conditions Earthing and protection against electric shock IEC For simplification, it is permitted to use the same value of Kas for the three-phase short circuit.

In this case, the three-fold zero-sequence current flows through the joint return. Impedances 2, between the starpoint of transformers and earth are to be introduced as 3 2, into the zero-sequence system without a correction factor.

The IEC standard terminology is used in the user interface and reports. This fault is beyond the scope of, and is therefore not dealt with in, this standard. In the case of figure 4, for instance, to the LV side.

Xk may be neglected. The generator impedance shall be transferred to the high-voltage side using the rated transformation ratio t. You can obtain the following values of short-circuit currents at the fault location for both maximum and minimum short circuit currents:.

The positive-sequence short-circuit impedance zat the short circuit location F is obtained according to figure 5a, when a symmetrical system of voltages of positive-sequence phase order is applied to the short-circuit location F, and all synchronous and asynchronous machines are replaced by their internal impedances.

For currents during two separate simultaneous single-phase line-to-earth short circuits in an isolated neutral system or a resonance earthed neutral system, see IEC For large transformers the resistance is so small that the impedance may be assumed to consist only of reactance when calculating short-circuit currents.

## IEC-60909 Short-Circuit in EasyPower

Figure 1 – Short-circuit current of a far-from-generator short circuit circuiy constant a. In this case special considerations beyond the scope and procedure given in this standard have to be taken into account see for instance 2.

You can also valculation the remote branch currents and remote bus voltages. In this standard it is calculated using a factor m for the time- dependent heat effect of the d. The phase angles displayed are relative to the applied equivalent voltage source being at zero angle. I quality of writing The calculation of the minimum steady-state short-circuit current in the case of a near-to- generator short circuit, fed by one or’ several similar and parallel working generators with compound excitation, is made as follows: Short-circuit currents and partial short-circuit currents for three-phase shott circuits between generator and unit transformer with or without on-load tap.