Modeling and experimental validation of internal faults in salient pole synchronous machines including space harmonics (original) (raw)
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A New Model of Synchronous Machine Internal Faults Based on Winding Distribution
IEEE Transactions on Industrial Electronics, 2000
A synchronous machine internal faults model based on the actual winding arrangement is described in this paper. Based on the winding function approach, the machine inductances are calculated directly from the machine winding distribution, thereby the space harmonics produced by the machine windings are readily taken into account. Moreover, the calculation of the machine inductances is made easier by the use of the machine electrical parameters instead of the geometrical ones. Simulation results for internal faults on a laboratory generator are compared with experimental results to verify the accuracy of the proposed model.
IEEE Transactions on Industrial Electronics, 2000
In large synchronous generators, the stator windings are usually parallel-connected in order to increase the machine current capacity. In analysis and modeling, the parallel windings are usually lumped into one equivalent stator winding since equal currents flow in these windings. However, when an internal fault occurs in the windings, the symmetry between the parallel windings is broken and different currents will flow in the parallel windings since unsymmetrical magnetic linkage may exist between the stator windings. The aim of this paper is to present a simulation model to investigate the internal fault currents of large synchronous generators with parallel-connected windings. This model is based on a modified winding function theory that takes into account all space harmonics. Moreover, the calculation of the machine inductances is made easier by the use of the machine electrical parameters instead of the geometrical ones. The simulation results illustrate the existence of different currents in parallel windings in the case of internal faults. Results are given for an implementation of the internal fault model in a real-time simulator of large power networks.
Numerical field calculation of stator winding faults in synchronous machines
COMPEL: The International Journal for Computation and Mathematics in Electrical and Electronic Engineering, 2009
The behaviour of a synchronous machine after a stator winding fault still is a little known issue. The paper discusses the analytical approach in [3], which calculates all possible winding connections, when absence of nonlinear material behaviour is assumed. Nonlinearity is only considered by adjusting the inductances after solving the differential equations, which at last is an unsatisfying aspect of the method. A more accurate method is given by the numerical field calculation, considering a two-dimensional time variant permeability distribution on the cross section of an electrical machine. The paper shows first results of transient time-stepping calculations of short circuits with respect on winding currents and radial forces on the rotor.
A Detailed Analytical Model of a Salient-Pole Synchronous Generator Under Dynamic Eccentricity Fault
IEEE Transactions on Magnetics, 2000
In this paper, a new detailed analytical model of a salient-pole synchronous generator (SPSG) under dynamic eccentricity (DE) is presented which is capable of accounting for the effects of magnetic saturation, rotor pole shoe saliency, and space distribution of stator phases and rotor winding. A real form of rotor pole shoes is taken into account in the proposed SPSG air-gap function distribution. Saturation effects incorporate into the air-gap function of SPSG as a simple proposed analytic equation that varies by the generator load and operating condition. Furthermore, variation of the resulted air-gap distribution of SPSG in the presence of DE fault is then computed precisely and the inverse air-gap function calculated using Fourier series in order to compute time varying self-and mutualinductances of stator phases and rotor winding via the modified winding function approach (MWFA). The computed inductances are used for simulation of SPSG and studying the frequency spectrum of stator line current in the presence of DE fault. It is shown that the results of proposed model are closer to the finite-element (FE) computation results compared to the available analytic models.
Effects of Turn to Turn Stator Winding Faults in Synchronous Generators - A Numerical Study
The effects of stator winding faults on the behaviour of a synchronous generator are of interest for predicting the severity of the occurring damage. The paper in hand describes the numerical transient field and net- work calculation for the sudden occurrence of stator wind- ing turn to turn short circuits within coil groups and be- tween different phases. For a 2-pole 775 MVA generator six different locations of short circuits varying in the num- ber of shorted turns and the position of the bypassed turns in the winding are investigated. Transient currents in the short-circuited windings as well as in the remaining stator coils are calculated, taking saturation into account. Addi- tionally, the unbalanced magnetic pull is determined and output as a function of time. The results of the calculations clarify the severity of such faults even if the machine is disconnected from the grid and de-energized within a very short period after the occurrence of the short-circuit. Index Terms—El...
Progress In Electromagnetics Research B, 2009
In this paper, winding function method (WFM), applied to a faulted synchronous generator, is modified and is used for online diagnosis of mixed eccentricity fault. For the first time, the static and mixed eccentricities are modeled in synchronous generators. A modified winding function (MWF) method introduced here is more precise compared with previous methods. This MWF enables to compute the air gap magnetic permeance accurately. Here, two or three terms of the infinity permeance series have not been used, but a closed form equation is employed for permeance evaluation. This leads to a very precise computation of the inductances of the faulted machine. Self inductances of the stator and rotor, mutual inductance of two stator phases and the mutual inductance of rotor and stator are obtained. Meanwhile, it is shown that static, dynamic and mixed eccentricities lead to the increase of the amplitude and occurrence of the distortion in the aforementioned inductances. Since calculation of inductances is the most important step for fault diagnosis of the machine, the proposed method improves the on-line diagnosis of the fault. Meanwhile, the spectrum analysis of stator current, obtained from experimental results, is illustrated.
IEEE Transactions on Industrial Electronics, 2011
This paper shows that a static eccentricity makes rise a double fundamental frequency ripple in the rotor current of salient-pole synchronous machines. This ripple leads, under conditions ruled by the stator windings, to precise signatures in the no-load voltage spectrum. Both rotor current ripple and voltage harmonics can be used for diagnosis. The fault-related voltage harmonics are theoretically previewed in this paper through analysis of the windings. Simulations performed by using the winding function approach confirm the theoretical predictions. A four-pole 15-kVA generator was used for experiments, featuring an innovative flange with exact and easy regulation of mixed-type eccentricities. Rotor current monitoring has advantages of single-sensor measure and accentuate fault sensitivity. Experiments also showed an additional rotor-rotation frequency ripple in the rotor current, in case of mixed-type fault.
Simulation of internal faults in synchronous generators
IEEE Transactions on Energy Conversion, 1999
An internal fault in the armature winding pf a synchronous generator occurs due to the breakdown of the winding insulation. In this paper a method for simulating internal faults in synchronous generators, using direct phase quantities, is described. Simulation results showing the fault currents, during a single phase to ground fault and a two phase t o ground fault, are presented.
2017
In this paper, a novel method is presented for detection and classification of the faulty phase/region in the stator winding of synchronous generators on the basis of the resulting harmonic components that appear in the terminal voltage waveforms. Analytical results obtained through Decision Tree (DT) show that the internal faults are not only detectable but also they can be classified and the related region can be estimated. Therefore, this scheme can be used to protect the synchronous generators against the various internal faults. Fuji technical documents and data sheets for an actual salient pole synchronous generator (one unit of an Iran’s hydroelectric power plants) are used for the modeling. Simulations in Maxwell software environment are presented. All the related parameters, such as B-H curve, unsymmetrical air gap and pole saliency, slot-teeth effect, and other actual parameters, are considered to obtain a comprehensive model to generate acceptable terminal voltage wavefor...