CE1 IEC (Première édition – ) (First edition – ) Courants de court-circuit dans les réseaux Short-circuit currents in three-phase. IEC Edition INTERNATIONAL. STANDARD. NORME. INTERNATIONALE. Short-circuit currents in three-phase a.c. systems –. Buy IEC SHORT-CIRCUIT CURRENTS IN THREE-PHASE A.C. SYSTEMS – PART 0: CALCULATION OF CURRENTS from SAI Global.

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For the short-circuit impedances of synchronous generators in the negative-sequence iex, the following applies with KG from equation 1 8: The effective resistance of the stator of synchronous machines lies generally much below the given values for RGf.

Currents calculated with equation 74 are larger than the real symmetrical short-circuit breaking. Skip to main content. Medium-voltage motors have to be considered in the calculation of maximum short-circuit current see 2.

All other active voltages in the system are assumed to be zero. The value should be obtained from the manufacturer.

## Short Circuits in Power Systems: A Practical Guide to IEC 60909-0, 2nd Edition

This is the only active voltage of the network 1. Systems at highest voltages of kV and above with long transmission lines need special consideration.

The capacitances of lines overhead lines and cables of low-voltage networks may be neglected in the positive- negative- and zero-sequence system. Additional information may be found in IEC During the initial stage of the short circuit, the negative impedance is approximately equal to the positive-sequence impedance, independent of whether the short circuit is a near-to-generator or a far-from-generator short circuit.

For higher temperatures than 20 OC, see equation 3. NOTE For some near-to-generator short circuits the value of id.

If the highest partial short-circuit current of the power station unit at the high-voltage side of the unit transformer with off-load taps is searched for, choose l-pT. These values cannot be used when calculating the aperiodic component id.

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Short-circuit currents and partial short-circuit currents for three-phase short circuits between generator and unit transformer with or without on-load tap. When a number of short circuits occur with a ifc time interval in between them, the resulting Joule integral is the sum of the Joule integrals of the individual short-circuit currents, as given in equation 1 Any divergence between the IEC Standard and the corresponding national or regional standard shall be clearly indicated in the latter.

This phenomenon is not dealt with in iex standard.

In a near-to-generator short circuit, the short-circuit current behaves generally as shown in figure 2. Example of a meshed network fed from several sources They may be neglected. Earthing and protection against idc shock IEC The equivalent voltage source is the only active voltage of the system.

It is only necessary to choose 60099-0 branches which carry partial short-circuit currents at the nominal voltage corresponding to the short-circuit location and branches with transformers adjacent to the short-circuit location. The zero-sequence system impedance Z,, of the motor shall be given by the manufacturer, if needed see 4.

The need for the calculation of minimum short-circuit currents may arise because of underexcited operation of generators low-load condition in cable systems or in systems including long overhead lines, hydro pumping stations. The correction factor Ks 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.

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. The impedance of the auxiliary transformer AT in figure 13 is to be corrected with KT from 3. 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 of the saturated no-load short-circuit ratio Impedance, absolute respectively relative isc Short-circuit impedance of a three-phase a.

Radial Network For grounded systems the influence of motors on the line-to-earth short-circuit current cannot be neglected. Short-circuit current-limiting reactors shall be treated as a part of the short-circuit impedance. All network feeders, synchronous and asynchronous machines are replaced by their internal impedances see clause 3.

The initial line-to-earth short-circuit current Iil in figure 3d shall be calculated by: CE1 TR–I read: Factor q for the calculation of the symmetrical short-circuit breaking current of asynchronous motors When calculating the partial short-circuit current I: For simplification, it is permitted to use the same value of Kas for the three-phase short circuit.

Currents during two separate simultaneous single phase line-to-earth short circuits and partial short-circuit currentsflowing through earth IEC ,- Short-circuit current calculation in three-phase a.

All other static converters are disregarded for the short-circuit current calculation according to this standard. The zero-sequence short-circuit impedance at the short-circuit location F is obtained according to figure 5c, if an a. IEC TR2- lire: