This calculation is based on IEC (, c), “Short-circuit currents in three-phase a.c. systems – Part 0: Calculation of currents” and. EasyPower offers a complete and accurate solution to short-circuit calculations in three-phase AC systems using the IEC standard. You can enter. IEC Edition INTERNATIONAL. STANDARD. NORME. INTERNATIONALE. Short-circuit currents in three-phase a.c. systems –.
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Example HV breaker ratings in the device library Figure 4: I quality of writing IkP Steady-state short-circuit current at the terminals poles of a generator with compound excitation Initial symmetrical short-circuit current r.
IEC standard specifies clock number notation and their respective phase angle shift for transformers. Permissions Request permission to reuse content from this site. In a system of low voltage breakers with ZSI, when the current through any circuit breaker exceeds the short time pickup its restraining signal is sent to upstream circuit breakers. The total short-circuit current in F1 or F2 figure 13 is found by adding the partial short-circuit current IL,, caused by the medium- and low-voltage auxiliary motors of the power station unit.
IEC-60909 Short-Circuit in EasyPower
I tables, charts, graphs, figures 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. Symmetrical Short-Circuit Breaking Currents I b For rotating machines the current contributions to short-circuit decays jec time. This first edition cancels and replaces IEC published in and constitutes a technical revision.
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 system of units SI. Synchronous machines generators, motors, or compensators with terminal-fed static exciters do not contribute to I k in the case of a short-circuit at the terminals of the machine, but they contribute to l k if there is an impedance between the terminals and the short-circuit location.
CE1 TR–l read: The impedances and z o L of low-voltage and high-voltage cables depend on national techniques and standards and may be taken from IEC or from textbooks or manufacturer’s data.
For the calculation of the initial short-circuit currents according to 4. This is the first step to obtaining most values. Radial Network Voltages at remote buses are also provided.
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An example for the introduction of the correction factors of equation 13 to the positive-sequence and the zero-sequence system impedances of the equivalent circuits is given in 2. Switches use the peak current to compare with making capacity. With these impedances the corrected equivalent impedances LK, z B K and ZCKshall be calculated using the procedure given in equation i i.
This method, therefore, does not necessarily lead to the maximum short-circuit current. Short-circuit currents decaying over time Methodology EasyPower uses the equivalent voltage source at the short-circuit location, symmetrical components impedance network, and the voltage factor c as described in section 2. Factor m for the heat effect of the d.
The initial short-circuit current at the short-circuit location F is the phasor sum of the individual partial short-circuit currents see figure It does not take into account adjustable time delays of tripping devices. Figure 2 – Short-circuit current of a near-to-generator short circuit with decaying a. Neglecting the -zero-sequence capacitances of lines in earthed neutral systems leads to results which are slightly higher than the real values of the short-circuit currents.
Operational data and the load of consumers, tap- changer position of transformers, excitation of generators, and so on, are dispensable; additional calculations about all the different possible load flows at the moment of short circuit are superfluous.
IEC Short-Circuit in EasyPower
The effective resistance of the stator of synchronous machines lies generally much below the given values for RGf. They do not contribute to the symmetrical short-circuit breaking current I, and the steady-state short-circuit current I k. EasyPower offers a ied and accurate solution to short-circuit calculations in three-phase AC systems using the IEC standard.
The type of short circuit which 600909 to the highest short-circuit current depends on the values of the positive-sequence, negative-sequence, and zero-sequence short-circuit impedances of the system.
Short Circuits in Power Systems: A Practical Guide to IEC 60909-0, 2nd Edition
T k i and the factor K derived in 4. Methods of Calculations 1 1.
Shunt admittances for example, line capacitances and passive loads are not to be considered when calculating short-circuit currents in accordance with figure 4b. You can enter equipment data and parameters via user friendly interface.
The method described above is for 3-phase short circuit. Also, all synchronous machines use the resistance R Gf in place of R G in accordance with section 3.