Iec 60909 short circuit calculation pdf

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# Iec 60909 short circuit calculation pdf

The system depicts a 20 kV network feeder connected to a V system via two step-down transformers. The short circuit currents are calculated at F1, F2 and F3. Comparison Report. Freq rtd. Ratio uk0 Res. Calulate Shor Circuit Button Figure 2. These differences can be further explained as a result of a three-figure number after the decimal comma used in the hand calculations in [1].

In this example, a high voltage a. The system depicts two network feeders connected to a kV system. Network feeder Q1 is connected to the kV system via two network transformers T3 and T4while network feeder Q2 is considered directly connected to kV. Additionally, several generators and asynchronous motors are considered. Calulate Shor Circuit Button Figure 3. First Edition, Related Papers.

Short-circuit Currents. By Thomas Thant.

By Pablo entrerrioss. By Predrag MaricL. Priklerand Srete Nikolovski. Short-circuit currents in three-phase a. By Antonis Athanasopoulos. By Sapanan Kittiwattanaphon. Download pdf. Remember me on this computer. Enter the email address you signed up with and we'll email you a reset link.

Need an account? Click here to sign up.EasyPower offers a complete and accurate solution to short-circuit calculations in three-phase AC systems using the IEC standard. You can enter. Short-circuit currents in three-phase a. 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.

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.

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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.

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. 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.

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 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.

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.To illustrate its application, the methodology is applied to a study medium voltage network with a variety of distributed generation resources.

Distributed generation resources are typically connected to the distribution network, at the low or medium voltage level. Therefore they contribute to the total fault level of the distribution grid. Hence, the basic requirement for permitting the interconnection of distributed generation resources is to ensure that the resulting fault level remains below the network design value.

The short-circuit currents is considered as the sum of an a. The Standard distinguishes between near-to-generation and far-from-generation short circuits. The methodology includes of a. In the present, two numerical methods for short-circuit calculations are used: superposition method and equivalent voltage source method. Superposition method gives the short-circuit current only in relation to one assumed amount of the load. Hence, it need not lead to maximum short-circuit current in the system.

For removing this lack, it was developed the equivalent voltage source method [2]. This source is defined as the voltage of an ideal source applied at the short-circuit location in the positive sequence system, whereas all other sources are ignored. All network components are replaced by their internal impedances see Fig.

Equivalent voltage source method In the calculation of the maximum short-circuit currents, the voltage factor c may be assumed equal to cmax, for any voltage levels see Tab.

According to Fig. If any distributed generation unit units is in the grid included, the resulting fault level is the sum of the maximum fault currents due to: the upstream grid, the various types of generators, the large motors connected to the distribution network. Other types of distribution generation units like fuel-cells, photovoltaics, small.

The calculation of contribution of the distribution generation units is not included in the IEC Only induction motors are dealt with, whereas the parameter values of synchronous generators provided in [4] are applicable to units of very large size [3]. The value of t depended on the protection and fault.

It is needed only for breaking and thermal current calculations. Special case of generator used for variable speed wind turbines is doubly-fed induction generator DFIG.

X G for the generator impedance [3]. Four distributed generation stations with total power cca 17 MW are connected to the medium voltage substation. They are three wind farms with six identical wind turbines and one small hydroelectric plant - SHP with three identical turbines. The data about case study network are given in Table 2. Case study Tab. Table 3 shows fault level calculation results for a three-phase fault at the MV busbars of the substation. Wind farm No. The reactor at the output of wind farm No.

The most important is that the design fault level of such a distribution network would be around MVA. Hence, the connection of amount of distributed generations 17 MW drives the fault level to unacceptably high values. From a fault level perspective, distribution networks are not designed to accept large amounts of distributed generations [3]. Slovensk stav technickej normalizcie, April Meter, M. Vpoet skratovch prdov v trojfzovch striedavch sstavch.

ABB Elektro, s. Boutsika, Th. Author address: Ing.Short circuit impedance calculation techniques based on IEC with correction factors for synchronous generators, power supply units, and transformers. Prior to this is the determination of the impedances of the electrical equipment. For many, the short circuit impedance calculation is a straightforward process but in IECthe determination of impedances for certain equipment requires a slightly different approach.

This is especially useful in the calculation of short circuit currents prescribed in the standard. With the nominal voltage at point Q U nQ shown in the figurethe impedance can be calculated using. For networks operating at a nominal voltage greater than 35kV, setting the impedance equal to the reactance is usually sufficient. It is also possible to use the above techniques in cases where the short circuit is fed through a transformer by introducing the transformation ratio such that.

The voltage correction factors presented in our introductory discussion on IEC were intended to account for the system pre-fault conditions. The calculation of maximum short-circuit current using applicable voltage factors, however, may not be sufficiently applicable to generators or power station units especially considering their subtransient behavior, i.

Accordingly, IEC introduced impedance correction factors specifically for generators and power station units. The impedance correction factor for generators directly connected to the system can be calculated using. For generators with a dedicated transformer, a single correction factor is applied to the sum of their impedances. It is as if the generator and its dedicated transformer are treated as one unit. As with synchronous generators, transformer impedance correction factor can be calculated using.

The readers are encouraged to review the calculations prescribed in IEC BS EN Short-circuit currents in three-phase a.

Detailed Implementation of IEC 60909 in EasyPower 10.0

## IEC 60909 Standard

Our prices are in Swiss francs CHF. We accept all major credit cards American Express, Mastercard and VisaPayPal and bank transfers as form of payment. Preview Abstract IEC is applicable to the calculation of short-circuit currents in low-voltage three-phase AC systems, and in high-voltage three-phase AC systems, operating at a nominal frequency of 50 Hz or 60 Hz.

It establishes a general, practicable and concise procedure leading to results which are generally of acceptable accuracy and deals with the calculation of short-circuit currents in the case of balanced or unbalanced short circuits.

This second edition cancels and replaces the first edition published in This edition constitutes a technical revision. This edition includes the following significant technical changes with respect to the previous edition: - contribution of windpower station units to the short-circuit current; - contribution of power station units with ful size converters to the short-circuit current; - new document structure.

Look inside. General aspects The following test report forms are related:. TC 73 - Short-circuit currents rss.Short-circuit currents in three-phase a. If only overexcited operation is uec, 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.

Request permission to reuse content from this site. Their preparation is entrusted to technical committees; any IEC National Committee interested in the subject dealt with may participate in this preparatory work. If the short circuit is a far-from-motor short circuit i. Any branch may be a series combination of several impedances.

Figure 20 describes this situation with balanced and unbalanced short circuits with earth connection at the short-circuit location F. For simplification, it is permitted to use the same value for IC as for the three- phase short circuit. If the Joule integral or the thermal equivalent short-circuit current shall be calculated for unbalanced short circuits, replace I: Transformer secondary short circuits.

Impedances between a starpoint and earth shall be introduced without correction factor. Depending on the product f. For simplification, it is permitted to use the same value of Kas for the three-phase short circuit. I cochez tout ce qui convient Je suis lehn: This part of IEC does not deal with the calculation of short-circuit currents in installations on board ships and aeroplanes. As a result, reversible static converter-fed drives are treated for the calculation of short-circuit currents in a similar way as asynchronous motors.

The zero-sequence short-circuit impedance at the short-circuit location F is obtained according to figure 5c, if an a. For grounded systems the influence of motors on the line-to-earth short-circuit current cannot be neglected. I education ci military ci I other This postulates that the electrical equipment has a balanced structure, for example in the case of transposed overhead lines. You are currently using site but have requested a page in the site. The text of this standard is based on the following documents: The initial short-circuit current at the short-circuit location F is the phasor sum of the individual partial short-circuit currents see figure For the short-circuit impedances of synchronous generators in the negative-sequence system, the following applies with KG from equation 1 8: The capacitances of lines overhead lines and cables of low-voltage networks may be neglected in the positive- negative- and zero-sequence system.

Transformers in Parallel When an impedance is present between the starpoint of the generator and earth, the correction factor KG shall not be applied to this impedance.

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.

### Calculation of Short-circuit IEC 60909

NOTE For some near-to-generator short circuits the value of id. For the examples in figures 1Ib and 1 IC, the initial symmetrical short-circuit current is calculated with the corrected impedances of the generator and the power station unit see 3. For the short-circuit impedance of synchronous generators in the zero-sequence system, the following applies with KG from equation 1 8: Calculation of a Cable 8. Table of contents Preface xi Acknowledgments xiii 1 Definitions: 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 IkP Steady-state short-circuit current ie the terminals poles of a generator with compound excitation Initial symmetrical short-circuit current r.

I In the case of minimum steady-state short circuits introduce c see 2. For simplification, it is permitted to the same value for as for the three- phase short circuit. The values of positive-sequence and negative-sequence impedances can differ from each other only in the of rotating machines.To browse Academia. Skip to main content.

Log In Sign Up. IEC Short-circuit currents in three-phase a c. Daniel Perez. To be published. Short-circuit current of a far-from-generator short circuit with constant a. Short-circuit current of a near-to-generator short circuit with decaying a.

Characterization of short circuits and their currents Short-circuit impedances of a three-phase a. System diagram and equivalent circuit diagram for network feeders Three-winding transformer example Phasor diagram of a synchronous generator at rated conditions Example for the estimation of the contribution from the asynchronous motors in relation to the total short-circuit current Short-circuit currents and partial short-circuit currents for three-phase short circuits between generator and unit transformer with or without on-load tap.

Example of a meshed network fed from several sources Factor p for calculation of short-circuit breaking current 1, Factor q for the calculation of the symmetrical short-circuit breaking current of asynchronous motors Linand il, factors for cylindrical rotor generators Factors ;Iminand il,for salient-pole generators Transformer secondary short circuits.

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Factor m for the heat effect of the d. Factor n for the heat effect of the a.

Voltage factor c Calculation of short-circuit currents of asynchronous motors in the case of a short circuit at the terminals see 4. The object of the IEC is to promote international co-operation on all questions concerning standardization in the electrical and electronic fields. Their preparation is entrusted to technical committees; any IEC National Committee interested in the subject dealt with may participate in this preparatory work.

International, governmental and non-governmental organizations liaising with the IEC also participate in this preparation.

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The IEC collaborates closely with the International Organization for Standardization ISO in accordance with conditions determined by agreement between the two organizations. Any divergence between the IEC Standard and the corresponding national or regional standard shall be clearly indicated in the latter.

The IEC shall not be held responsible for identifying any or all such patent rights. This first edition cancels and replaces IEC published in and constitutes a technical revision. Annex A forms an integral part of this standard. At this date, the publication will be 0 reconfirmed; 0 withdrawn; 0 replaced by a revised edition, or 0 amended. Systems at highest voltages of kV and above with long transmission lines need special consideration.