# CEI IEC TR 60909-4-2000 pdf download

**CEI IEC TR 60909-4**-2000 pdf download.Short-circuit currents in three-phase a.c. systems – Part 4: Examples for the calculation of short-circuit currents.

This part of IEC 60909 is a technical report intended to give help for the application of IEC 60909-0 for the calculation of short-circuit currents in 50 Hz or 60 Hz three-phase a.c. systems.

This technical report does not include additional requirements but gives support for the modelling of electrical equipment in the positive-sequence, the negative-sequence and the zero- sequence system (clause 2) and the practical execution of calculations in a low-voltage system (clause 3), a medium-voltage system with asynchronous motors (clause 4) and a power-station unit with its auxiliary network feeding a large number of medium-voltage asynchronous motors and low-voltage motor groups (clause 5.

The three examples given in clauses 3,4 and 5 are similar to those given in TEC 60909 (1988) but they are revised in accordance with IEC 60909-0. which replaces it.

A subclause is added to the example in clause 3 to give a comparison between the results found with the app’ication of the equivalent voltage source at the short-circuit location following the procedure given in IEC 60909-0 on the one hand. and results found with the superposition method on the other hand, taking into account different load-flow conditions before the short circuit.

Clause 6 of this technical report gives the circuit diagram and the data of a test network and the results for a calculation carried out in accordance with IEC 60909-0, to offer the possibility for a comparison between the results found with a digital program for the calculation of short-circuit currents and the given results for ‘k’ i. ‘b’‘k’ l and in a high-voltage network with power-station units, generators, asynchronous motors and lines in four different voltage levels 380kV, 110 kV, 30kV and 10kV.

1.2 Reference documents

IEC 60038:1983, IEC Standard voltages

IEC 60909-0:2000. Short-circuit currents in three-phase ac. s stems — Part 0: Calculation of currents

IEC 60909-I: 1991, Short-circuit current calculation in three-phase ac. systems — Part 1:Factors for the calculation of short-circuit currents in three-phase a.c. systems according to

IEC 60909

IEC 60909-3:1995. Short-circuit currents in three-phase a.c. srsfrrns — Part 3: Currents during Iwo separate simultaneous single phase line—to-earth short circuits and partial shori-circuit currents flowing through earth

IEC 60865—1:1993. Short-circuit currents — Calcukirion of” effrcrs — Part I: Defiiiiiions and calculation methods

1.3 Definitions, symbols and indices, and equations

The definitions, symlols, indices and the eqUations are the same as those used in IEC 60909-0.

2 Positive-sequence, negative-sequence and zero-sequence impedances of electrical equipment

In addition to clause 3 of IEC 60909-0. modelling and calculation of the positive-sequence and the zero-sequence impedances of electrical equipment is given. In most cases the negative- sequence impedances are equal to the positive-sequence impedances when calculating the initial short-circuit currents, but see 3.6.1 of IEC 60909-0 and IEC 60909-2.

2.1 Overhead lines, cables and short-circuit limiting reactors

Figure 1 demonstrates the meaning and the principal measurement of the positive-sequence and the zero-sequence impedances of overhead lines with one circuit LI. L2. L3.CEI IEC TR 60909-4 pdf download.