CALCULATIONS OF GENERATOR SOURCE SHORT- CIRCUIT CURRENTACCORDING TO ANSI/IEEE AND IEC STANDARDS, WITH EMTP VERIFICATIONS. J.C. Das, FIEE, FIEE, FIE, PE AMEC, INC. Atlanta, Georgia Abstract: For the interruption of a large generator source-short-circuit current, a current zero may not be obtained at the contact parting time of the circuit breaker. Large generators which have high X/R ratio, and depending upon the relative impedances and time constants the dc component can be higher than the ac decaying component delaying the occurrence of current zero well beyond contact parting time of the circuit breaker. The subject is well addressed in the current literature, though not the calculations of it. This paper presents calculations of a large practical generator using ANSI/IEEE and IEC standards with verifications of results using EMTP. It demonstrates large differences which impact the selection of generator circuit breaker interrupting duties. UAT, (3) from the generator itself. However, the generator breaker sees only the component (3) contributed by the generator. Similarly for fault at F1, the generator breaker sees the sum of the utility source and auxiliary distribution system short-circuits current contributions, but not the contribution from the generator itself. While selecting a generator breaker, higher of these two fault currents at F1 and F2 should be considered. Generally, the generator contribution for fault at F2 gives rise to higher asymmetry than the fault at F1,because large generators have a higher X/R ratio compared to the short-circuit X/R ratios in the utility systems. I. INTRODUCTION Fig. 2 shows a bus connected generator in an industrial distribution system running in synchronism with utility. Again the faults at F1 and F2 can be considered and the generator breaker sees only the generator contribution for a fault at F1. Consider system configurations shown in Fig. 1 and Fig.2. Fig.1 shows a generating station, the generation voltage is stepped up to 500 kV, the ratings of generators and transformers are not shown for generality of the discussions. Generators 2 and 3 have a generator breaker, while generators 1 and 4 do not. Provision of a generator breaker makes it possible to use the generator step up transformer as step down transformer during start-up. (The relative merits of providing a generator breaker are not discussed. In-line generators breakers rated at 50 kA continuous current and short-circuit interrupting current up to 250 kA are available.) Consider fault locations F1 and F2 in Fig.1. The generator breaker short-circuit duties are of interest. For a fault at F2, there are three contributions of the short-circuit currents; which are: (1) from the utility source, (2) from the auxiliary distribution system rotating loads through ANSI/IEEE Std. C37.010 [1] cautions that the longer dc time constants could cause a problem with SF6 type puffer circuit breakers. The interrupting window, which is the time difference between the minimum and maximum arcing times, may be exceeded because of delayed current zero, and arc energy and interruption window are of concern. The calculation methods described in this standard are qualified that the E/Z method of calculation with adjustments of ac and dc decrements can be used provided the X/R does not exceed 45 at 60 Hz, i.e., the dc time constant is not more than 120 ms. Yet, the commercial software available in the USA is based upon the empirical calculations of the short-circuit currents according to ANSI/IEEE standard [1], and unfortunately the industry ignores the qualifying statement of dc time constant with respect to short-circuit calculations. Key terms: generator source asymmetrical short-circuit current, degree of asymmetry, lack of current zero at contact separation. 3. Ra is the armature resistance. The symmetrical component does not exceed required generator source symmetrical capability. large utility generating station. X d" Ta = 2πf (Ra + Radd ) 2.48 kV Bus 2 Generation Low-voltage auxiliary loads Fig. Radd is the added arc resistance and X”d is the subtransient reactance and f is the system frequency.013 [2] for generator circuit breakers. Ref. Where Ta is the armature time constant. [2] recognizes this asymmetry and states that at the time of current interruption.16 kV Bus 1 Aux Transf. This reduces the time constant of the dc component and forces it to decay faster: 1. Transf.16 kV Bus 2 52 52 Generation Medium-voltage auxiliary loads Aux. . The total source current does not exceed the required generator-source asymmetrical capability. The degree of asymmetry from generator source does not exceed 110%. 1 52 52 4.1. C37. states that any combination of ac symmetrical and dc components of short-circuit currents are permissible provided the following conditions are met at the primary contact parting time: from generator source short-circuit current may exceed 110% in the large generators being manufactured today.48 kV Bus 1 (1) 0.IEEE std. It is the second condition that is discussed in this paper. the arc fault resistance will add to the generator armature resistance. A diagram of connections. 2 Third standby source of power Interlocks and auto switching 0. which shows that asymmetry 52 52 52 52 52 52 500 kV double bus 52 52 52 GSU1 52 52 52 GSU3 GSU2 GSU4 F2 52 G G1 52 G UAT2 UAT1 F1 G2 52 52 G3 G4 Interlocks and auto switching 4. the current is reduced by a factor of 0. the current interruption is equivalent to interrupting a dc current. The IEC standard showing the examples of short-circuit calculations. II. Fig. It is prudent to consult the manufacturer for this application. the current interruption in this mode will be equivalent to that of interrupting a dc current without current zero crossing. which have been withdrawn.Fig. zero crossing may not occur after several periods of contact opening time. the short-circuit changes to a two-phase fault. Generator circuit breakers capable of interrupting with 130% asymmetry at the contact parting time are commercially available. while the asymmetry in the other two phases will be minimum and these phases will interrupt first. When no current zero is obtained. But caution has to be exercised that all ANSI/IEEE rated breakers may not be suitable for high asymmetrical current interruption. 3 shows this effect on decay of the dc component and the current zero obtained at the contact parting time. When a two-phase fault escalates to a three-phase fault. A short-circuit in the phase having zero asymmetry (depending upon the instant of fault on the voltage wave).2. With no current zero. respectively. AC CURRENT INTERRUPTION A short-circuit current with maximum asymmetry in one phase may not have zero crossing in many periods. Note that some examples of calculations were included in earlier 1988 issue of this standard. which will further prevent short-circuit current envelope from crossing the zero-axis. The high voltage circuit breakers have limited current interrupting capability in this mode. A current zero obtained at the contact parting time with added arc fault resistance. Short-circuit current profiles for “far from” and “near to” the generator are shown in Figs. However. The high voltage circuit breakers have limited interrupting capability in this mode of operation. Some modern technologies in ac circuit breakers intended for generator applications . and the vacuum technology may also achieve the same results. . does not discuss the asymmetry at the contact parting time of the breaker. A bus connected industrial generator IEC standard [3]. IEC may adopt IEEE standard [2] for the generator breakers.3. will be interrupted first. respectively. The vacuum interruption technology may also achieve the same results. the performance with arc fault resistance is difficult to simulate and demonstrate even in a test station. unless specifically designed to introduce resistance in the arc fault path at current zero. Fig. Current technologies in some SF6 breaker designs use arc rotation techniques to force a current zero.866. The available continuous current rating and the interrupting symmetrical rating of generator breakers at the upper end is 50 kA and 250 kA. say SF6 designs. 1 and 2 of this standard. use arc rotation techniques to force a current zero. There is no discussion of not obtaining a current zero at the contact parting time of the breaker. part.4 is yet to be published. P = rated power.330 Ta circuit The calculations in this paper follow a sample example in [2].615 Three-phase short0.434 Subtransient X’’q 0.022 T’’do subtransient Field time constant data quadrature axis Open circuit T’qo 0.230 Subtransient X’’d 0. 2-pole. (3) EMTP simulation.135 XLM. (2) IEC standard and. All time constants are in seconds. and t is the time in seconds. V =rated maximum voltage. All other symbols are defined in Table 1. Table shows saturated reactance’s. from [2]: ⎤ ⎡⎛ 1 1 ⎞ −t / T " ⎥ ⎢⎜⎜ " − ' ⎟⎟e d P 2 ⎢⎝ X d X d ⎠ ⎥ I asym = ⎥ cos2ωt ⎢ V 3⎢ ⎛ 1 1 ⎞ −t / Td' 1 ⎥ ⎟e +⎜ − + ⎢⎣ ⎜⎝ X d' X d ⎟⎠ X d ⎥⎦ ⎡⎛ 1 ⎤ 1 ⎞ ⎢⎜ " + " ⎟e−t / Ta ⎥ ⎜X ⎟ X ⎢ ⎥ d q P 2 ⎝ ⎠ + ⎢ ⎥ V 3 ⎢ 1⎛ 1 ⎞ 1 ⎥ ⎜ ⎟ ⎢− 2 ⎜ X '' − X " ⎟ cos2ωt ⎥ q ⎠ ⎣ ⎝ d ⎦ (2) Where Iasym is the generator source asymmetrical current.UEX under excited Per unit reactance data. 18 kV.015 T’’ d subtransient Open circuit 0. shows the manufacturer’s data.150 Saturated negative 0.OXE overexcited Leakage reactance. All data is in per unit on generator MVA base of 234 MVA. in the phase with maximum asymmetry and the generator unloaded is calculated using the following equation. ω is the angular frequency.150 XLM. which is limited to the modeling and the calculations in this paper. (198. which are used in the short-circuit calculations 1V. 0..120 Transient X’d 0.451 Open circuit 0. The second harmonic term in this equation is neglected.046 T”q0 subtransient Armature dc component time constant data Three-phase short0. direct axis Open circuit T’do 5. A generator of 234 MVA.56 SCR (short-circuit ratio).150 X2v sequence Leakage reactance. is calculated by three methods: (1) IEEE standard. high resistance grounded and connected directly to a step up transformer is considered. If the generator is operating underexcited at leading power factor a higher asymmetry can be expected at the contact parting time [2]. Generator Manufacturer’s Data Description Symbol Data Per unit reactance data. 0. 350 field volts. wye connected 0. Table 1. . ANSI CALCULATIONS Generator source short circuit current. GENERATOR SOURCE SHORTCIRCUIT CALCULATIONS The generator source fault current. A comparative analysis of the results of these calculations is made for further discussions and analysis. 60 Hz. direct axis Synchronous Xd 2. for a practical machine.III. Note that there is no commercially available software computerizing the short-circuit calculations Table 1.140 Generator effective X/R 125 X/R Field time constant data.597 T’d circuit transient Short-circuit 0.85 power factor. 7505 rated current.858 Transient X’q 0. 0. quadrature axis Synchronous Xq 1.9 MW). • Asymmetry factor = 135. ANSI/IEEE Short-circuit calculations ignore the prior loading of generators and motors and the calculations are. consisting of ½ cycle tripping delay and 2. For near to generator faults.22 kA. For the calculations of peak short-circuit current with sufficient accuracy. This is rather an oversimplification of a complex transient phenomenon. The asymmetry factor α is given by: α= dc component 2 symmetrical int errupting current (3) And the total asymmetrical interrupting current is given by: I total . In multi-machine system speeds of all machines will change. which considers ac and dc decay: RGf = 0. IEC distinguishes between the generators directly connected to systems and generators and unit transformers of power station units. this gives an X/R of 125.5 cycles opening time. 8. type of excitation system for synchronous generators. Thus. and 10]. and all the symbols have been described in Table 2. specifies a dc component decay time constant of 133 ms.80 kA. Using the data from Table 2 and considering a 5 cycle breaker. from [1]. Ref. which correlates with the data supplied by the manufacturer in Table 2. • Dc component = 59. which forms basis of further calculations. except to present the calculated results. V. • Generator source ac symmetrical interrupting current: 30. Using appropriate values from Table 2. as discussed here. as these strive to reach a mean retardation through oscillations [6]. made at the rated voltage. The effective resistance of the generator used in the short-circuit calculations is calculated from the following expression.05 times the subtransient reactance for machines of UrG > 1 kV and SrG ≥ 100 MVA. The step-by step details of the calculations are not shown. It implies that a current zero will always be obtained at the contact parting time due to added arc resistance at the current interruption.5% and the current zero is not obtained. while the prime mover output cannot change abruptly. Required asymmetrical interrupting capability for threephase faults is 110% of the peak value of the symmetrical generator source current. generally. i.asym = (ac sym ) 2 + (dc) 2 (4) An important parameter of calculation is the X/R ratio. the generator and transformer is considered a single unit.2 kA peak. type of network. IEC CALCULATIONS There are analytical and conceptual differences between the ANSI/IEEE methods of short circuit calculations and IEC [7. (meshed or radial). • Total rms asymmetrical interrupting current at contact parting=66. (6) . however. Tracking each contributing source current throughout the system is necessary. preloading. the terminal voltage will be zero.9 kA rms. 9.The equation (2) considers that the generator is operating at no-load. RG = X 2v 2π f Ta (5) Where RG is the generator effective resistance. so that these generate their share of synchronizing power in the overall impact. minimum time delay and the determination whether the contribution is from near to (local) or far from (remote) short-circuit sources. For a terminal fault. and power supplied to the load reduces to zero. with contact parting time of 3-cycles. the calculated short-circuit currents are: • Close and latch: 112. rotor angle and frequency will all change. IEC requires calculation of initial symmetrical shortcircuit current in each contributing source.e. It is not the intention to go into the details of the IEC calculations. The paper confines to the basis laid out in the standard. and each of these component currents is a function of X/R ratio. [3] recommends a fictitious resistance. In practice the generator will be connected to an interconnected system. and its terminal voltage. [2].. the generator will accelerate. with detail modeling and Park’s transformations. ibsym = 38. which is a combination of its own self inductance.SO Z G (7) Where c is the IEC voltage factor =1. calculated from the expressions in [3]. The field flux is directed along d-axis.90 kA. EMTP SIMULATION Short-circuit calculations are conducted using EMTP program. . Compare this calculation with IEEE calculation of generator source symmetrical fault current calculated as 30. Also the generator is considered at no-load.SO=1. Idc=60. The aperiodic dc component at minimum time delay is calculated from equation (64) of [3]: " I dc = 2 I kG e −2πftR / X (12) Here X/R =20 cannot be used. It is given by the following expression: K G . and its mutual inductance with respect to phases b an c. The calculations described above omit many steps and explanations. 9 and 10] provide further reading. from (7). φrG =0.6 peak . 7. Generator peak current is given by: " i pG = χ 2 I kG (10) Where ipG is the peak short-circuit current (equivalent ANSI /IEEE close and latch current). Consider phase ‘a’ inductance. This gives i pG = 131. Using the values from Table 2. VI. There is considerable difference in the calculated results using the same data. Conceptually this transformation is shown in Fig. given by: Z G = RGf + jX d" (9) " Then. EMTP uses Park’s transformation. All these inductances vary with the position of the rotor with respect to the stator. The generator breaking (ANSI interrupting) current for minimum time delay of 0. along q-axis. Consider that the field winding is cophasial with the direct axis and also that the direct axis carries a damper winding. it is ignored as ANSI/IEEE methods and EMTP simulations are made with rated generator voltage. the asymmetry factor is 112% versus 135% with ANSI calculations. i. ZG is generator impedance and K G. The partial initial short-circuit current of the " generator.10 ZG is the generator impedance. cautions that the actual generator resistance can be much lower and the value arrived from (5) can not be used for calculating the aperiodic dc component of short-circuit current. this gives an X/R ratio of 20. Ref. Thus. IEC [3]. I kG .97 kA .73 kA. RGf is the fictitious generator resistance and SrG is its rating in MVA.SO is a defined factor for generators and unit transformers of the power stations. however.10 for maximum short-circuit current calculations for medium and high voltages (>1-230 kV). For the purpose of this calculation. is given by: " I kG = cU rG 3K G . the machine generated voltage is at right angles to it. [3. as calculated before. SO = 1 c " 1 + pG 1 + X d sin φ rG (8) Where φrG is the load power factor angle prior to the generator fault and factor pG considers generator voltage regulation. therefore.. The inductance matrix of a synchronous machine reactance in the stator frame of reference is not constant and varies with the position of the rotor with respect to the stator coils. which is much lower than the X/R ratio of 125 calculated using (5).05 s (ANSI contact parting time) is: " ibsym = μI kG (11) Where ibsym is the symmetrical component of the generator source fault current and μ is the multiplying factor. Substituting all the values. The q-axis also has a damper winding. I kG = 49.e. UrG is the generator rated voltage.Where UrG is the generator rated voltage. This calculation gives. 4. The factor χ can be ascertained from the X/R curves in [3] or from analytical expression in [3]. KG. which is a powerful analytical transformation for the study of synchronous machine behavior.5 kA. Using X/R=125. v . K = 3/2 These all pertain to transformed d-axis. These calculations are not shown. These details are not presented. Table 2. The stator parameters are transferred to the rotor parameters. To illustrate Park’s transformation and inverse Park’s transformation Mfkd = mutual inductance between field and damper windings id. voltages and flux linkage vector and P the transformation matrix. field and damper windings. which can be first externally calculated from the manufacturer’s data in a-b-c frame of reference. The input of this data into EMTP modeling converts it to 0dq axes.Park’s transformation describes a new set of variables. [16] may be seen for the EMTP model. Refs [11-15] provide further reading. Manufacturer’s data is always supplied in the stator frame of reference. Using matrix notation: i0 dq = P iabc v0 dq = P v abc (13) λ0 dq = P λabc Here the matrix and vectors are denoted by a top bar. such as currents.4. i . if. subscript 0dq refers to transformed axes and subscript abc refers to stator frame of reference. . stationary with respect to the rotor. Similar transformation applies to q-axis. This rotating field is produced by constant currents in the fictitious rotating coils in d-q axes. EMTP routine calculates the transformed parameters based upon the input manufacturer’s data. Fig. voltages and flux linkages in 0dq axes. Ref. For example the decoupled flux matrix in d-axis can be written as: λd Ld λ f = KM fd λkd KM dkd KM fd Lf M fkd KM dkd id M fkd i f Lkd ikd (16) Where Ld = self inductance of the armature Lf = self inductance of the field winding Lkd =self inductance of the damper winding Mfd =mutual inductance between the field and armature windings Mdkd = mutual inductance between armature and damper windings Fig. ikd =Currents in the direct axis.4 (b). It is not the intention to go into the details of the synchronous machine modeling theory or the calculation routines in EMTP. Also the system inertia constant and mechanical damping has been modeled. The abc constants in the stator windings produce a synchronously rotating field. λ are currents. It can also accept the transformed parameters in 0dq axes directly. it is the same plot as shown in Fig. and the current zero is further delayed compared to Fig. It is seen that in phase c.29 PF. This is correct. VII.4 Mvar. 8(a) shows the generator operating at no-load. Fig. as a lagging power factor increases the internal voltage behind the machine transient reactance. Ref. except that the simulation is carried for 500 ms. 93. This is clearly shown in the EMTP simulation in Fig.The three-phase short-circuit current profile is shown in Fig. b and c. The calculated values at the contact parting time are: • Generator symmetrical interrupting /breaking short circuit current = 33. the asymmetry does change with the power factor and prior load.5 kA • Asymmetry factor = 131%. Fig. which shows considerable differences in the asymmetry factor. 8 (a). and conversely a leading power factor decreases it. 7 for phase c. see text . The first cycle peak current is reduced from 132 kA at no-load to 129 kA and the asymmetry at contact parting time is increased from 131% at no load to 142%. a generator will not be operated at such a low power factor. because I kG is common to these equations. 0. current zero is not obtained for a number of cycles. The results are read from the computer outputs. however. This simulation is. Mvar= 92.3 MVA.Similarly a leading power factor will " decrease I kG . Table 3 shows the comparative results obtained with the three methods of calculations. calculated by the three methods. However from (11) and (12) it does not change the asymmetry at " the contact parting time. to show the impact of low load and very low power factor. The comparative results are shown in Table 2. EMTP simulations of the generator shortcircuit currents.7.59 kA rms • Dc component = 62.[17] describes a geometric construction for the calculation of ac symmetrical and dc components from offset asymmetrical wave. Practically. But. THE EFFECT OF POWER FACTOR The load power factor (lagging) in IEC " calculations will increase I kG (equation (7)). 7 for phases a. 8(b) shows the simulation with prior load on the generator as follows: MW=28. while absorbing power from the power system. Fig. 8. except the simulation carried for 500 A power system engineer must be cautious when applying calculation methods according to accepted standards.85 power factor directly connected to a 12.05 Asymmetry factor 30. Dc component. Such large units in the industrial distribution pose the same problem of higher asymmetry at the contact parting time as the directly connected utility generators through step up transformers. The size of a generator that can be bus connected in an industrial distribution is approximately limited to 100 MVA.47 kV utility transformer. also powered by a 30/40/50 MVA.50 33. X q'' = 15. 0.22 66.50 70. generator unloaded.2 131. The delayed current zeros can also occur on short- . Following are the specific parameters of the 81. When using IEC calculations.476 s Considering a 5-cycle symmetrical rated breaker.Table 2 Comparison of Calculations using IEEE/IEC Standards and EMTP Simulations Calculated Parameter IEEE IEC EMTP Close and Latch . (a) EMTP simulation of the generator short circuit current. phase C. 10.9. X d = 201. 28 MW. and the plant running load is 45 MVA.90 62. IX. 7.2. with generator loaded. 115-12. 0.80 60.73 71. the excess generated power is supplied into the utility system. as an acceptable level of short-circuit should be maintained at the medium voltage switchgear and the downstream distributions.8.47 kV.638 s.82 MVA. same as in Fig. There can be differences in the calculations using the same data.82 MVA generator shown in Fig. The two sources are run in synchronism. The example of calculation in this paper clearly demonstrates that asymmetry at contact parting time can be even 130% or more. Td' = 0. 8. kA RMS (IEC ibasym) 112.90 38. kA peak ( IEC peak short-circuit current) Generator source Interrupting kA sym. CONCLUSIONS Fig.90 135% 112% 131% ms. Ta = 0. 2 shows a generator of 81. RMS (IEC symmetrical breaking current ibsym.015 s. X d' = 22. Td'' = 0.29 leading power factor VIII. The calculations are not carried out using IEC standards and EMTP simulation.47 kV bus. 12. kA Total asymmetrical. actual X/R specified by the manufacturers should be used for calculation of aperiodic dc current at the contact parting time.59 59.60 132.3. the asymmetry at the contact parting time from (2) and (3) = 132%. (b) short-circuit current in phase C. X d'' = 16. CALCULATIONS FOR BUS CONNECTED GENERATOR Fig. . C37. [10] Berizzi A. ATP Rule Book. IEEE Trans. Rouss. BBC Review. [13] Hancock NN. IEEE Standard for Generator Circuit Breakers Rated on Symmetrical Current Basis. [7] Das JC. [11] Adkins B. The manufacturers can supply test certificates showing successful interruption at this asymmetry. Sieling Harry. Vol. 2001-07..” IEEE Trans. Power System Analysis.Calculation of Currents. No. 19 and 20]. IEEE Press. The possibility of catastrophic failure exist when this phenomena is ignored and short-circuit currents are not properly calculated. with cogeneration facilities. 1964. [18. Short-Circuit Calculations According to IEC Standards. 1994. Chapman and Hall. All generator breakers in the market may not meet these criteria. May/June 1993. Power SystemControl and Stability. though this will increase the fault energy let-through and will have profound impact on stability of the power system. In general. Ames. Stafford P.4. Lam P. 0. Baden. CRC Press. 1099-1106. Vol. E. [15] Boldea Ion. Chapter 8. [4] Ragaller K. 66. Marcel Dekker. April 1979.circuits in large industrial systems. Short-Circuit Currents in ThreePhase AC Systems. Brussels. Proceedings of 8th International Symposium on Short-Circuit Currents in Power Systems. C37. [6] Jacobs Dunki JR. FL. pp. Developments in generator circuit breakers have produced designs.-0.29. [3] IEC 60909. Industry Applications. A. Plenum Press. 1964. Short-Circuit Calculations— ANSI/IEEE & IEC Methods. 2007. 2005. 1978.. pp 11801194. 1997. A Comparison of ANSI-based andDynamically Rigorous Short-Circuit Current Calculation Procedures. One solution to the problem can be purposely delaying the opening of the breaker. 1A: Iowa State University Press. Synchronous Generators. Fouad A. 24. X.2002. July/August. Factors for Calculation of Short-Circuit Currents in ThreePhase AC Systems According to IEC 60909-0. 1991.. [16] Canadian/American EMTP User Group. Boca Raton.. New York.013a. Trans. Interruption of Short-Circuit Currents in High Voltage AC Networks. Analysis of Faulted Power Systems. 1992.3. Current Interruption in High Voltage Networks. 1988. Pergamon Press. REFERENCES [1] ANSI/IEEE Std. pp 625-630. Comparison of ANSI and IEC 909 Short-Circuit Current Calculation Procedures. Amendment 1: supplement for use with Generators rated 10-100 MVA. [12] Anderson PM. Also IEC 60909-1. Vol. Portland Oregon. [14] Anderson PM. New York [9] Knight Gene.. No. London. 1999.013.30. Short-Circuit Current Calculations: A comparison between Methods of IEC and ANSI Standards Using Dynamic Simulation as Reference. 1991. Industry Applications. Vol. C37. Massucco S.1988. 1997 and IEEE Std. and Zanin D. Silvestri A. Edinger.010. IEEE. New york. 1973. [8] Das. Similarities and Differences. [5] Braun A. Industry Applications Society. The manufacturer should be consulted for applicability of their breakers to interrupt the high asymmetry currents as demonstrated by testing. Guide for AC High Voltage Circuit Breakers Rated on Symmetrical Current Basis. which can handle 130% asymmetry. Matrix Analysis of Electrical Machinery. [2] IEEE Std. a generator breaker capable of interrupting 130% asymmetrical current seems to be an appropriate application in most cases. The General Theory of Electrical Machines. JC. Vol 17. C37. Willieme JM. [20] Dufournet D. BBC Review 56.[17] ANSI/IEEE Std. pp 963-969. IEEE StandardTest Procedure for AC HighVoltage Circuit Breakers rated on a Symmetrical Current Basis. 484-493. 1999. 1969. Power Delivery. Vol. 2002. and Montillet GF. Interrupting Sudden Asymmetrical Short-Circuit Currents without Zero Transition.09. 2001. IEEE Trans. Comparison of Generator Circuit Breaker Stresses in Test Laboratory and Real Service Condition. [19] Canay IM. Power Delivery. . Design and Implementation of a SF6 Interrupting Chamber Applied to Low Range Generator Breakers Suitable for Interrupting Currents Having a Non-zero Passage. Warren L. pp 415-421. pp. [18] Canay IM. Oct. 16. IEEE Trans.
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