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This paper presents a non-invasive procedure to detect inter-turn short circuit faults in the stator windings of AC electrical machines. It proposes the use of the stray external magnetic field measured in the vicinity of the machine to determine stator faults. The originality introduced by this procedure is the analysis method presented in the pap...
Contexts in source publication
Context 1
... model of a faulty winding is presented in Figure 4 where the whole phase winding is composed of an elementary healthy section and one with short circuit turns. For both structures, it is assumed that the magnetic reaction of the rotor is such that only the fundamental of the stator currents for a running at no load will be considered to characterize the air-gap flux density. ...
Context 2
... model of a faulty winding is presented in Figure 4 where the whole phase winding is composed of an elementary healthy section and one with short circuit turns. For both structures, it is assumed that the magnetic reaction of the rotor is such that only the fundamental of the stator currents for a running at no load will be considered to characterize the air-gap flux density. ...
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Citations
... In practice, a good relay protection can not only respond to unexpected situations in time to avoid the further expansion of the accident scale, but also isolate and mark the fault nodes in a timely and effective manner, providing a great boost to the progress of subsequent restoration work [25]. The power system relay protection device is an automatic device used to carry out line faults and abnormal situations in which the circuit breaker trips and issues warning signals. ...
With the progress of society and the iterative improvement of infrastructure construction, the power grid transmission lines have also entered an era of intelligence. The national distribution system has made ensuring the regular operation of the distribution network as well as prompting troubleshooting and detection its top priority. Research on fault diagnosis for 35 kV single-ended radial distribution networks is still in its infancy compared to other hot topics in the industry, such as short-circuit fault detection and fault node localization. This study adopts the 35 kV single-ended radial distribution network as a model, detects fault lines via the traveling wave method, and accurately locates fault nodes using the wavelet conversion method, hoping to quickly identify and locate fault nodes in distribution networks. The experimental results demonstrate that the research method can quickly identify the faulty line and carry out further fault node location detection. The final obtained fault distance is 1.19 km with an actual error of only 0.16 km; the maximum relative errors are only 0.33 km and 0.21 km when the initial phase angle and transition resistance parameters are changed, respectively; and the error amplitude fluctuations are essentially stable. The experimental results also demonstrate that the research method can quickly identify the faulty line and carry out further fault node location.
... В роботі [4] запропоновано метод аналізу інформації від датчиків магнітного потоку, який не вимагає даних про нормальний стан синхронного генератора. Даний метод заснований на використанні магнітної несиметрії, що створюється полюсами ротора у випадках пошкоджень. ...
The purpose of this study is to develop a mathematical model of a synchronous generator to study its modes of operation in the case of asymmetric damage to the phases of the stator winding, namely twisting, the use of which will make it possible to improve relay protection systems against twisting of the stator winding of a synchronous generator. Transverse differential protection is used to protect synchronous generators from winding circuits. However, such protection can be used only on generators with parallel branches in the phase of the stator winding. In the work, a mathematical model of a synchronous generator was developed, which allows to study the transient processes of the generator in case of the appearance of turn short circuits in the stator winding. This mathematical model is based on differential equations written for the stator phase axes a, b and c. An algorithm for calculating transient processes in a synchronous generator is proposed. In turn-to-turn circuits of the stator winding, which is based on the fourth-order Runge-Kutt numerical integration method. With the help of the developed mathematical model, the values of currents and voltages of the generator were calculated in the case of short-circuits of the stator winding for the TVB-200-2 turbogenerator. The results of mathematical modeling of the transient processes taking place in the TVB-200-2 generator when closing a different number of turns of the stator phase showed that the reduction of the fundamental harmonic voltage at the terminals of the generator in the damaged phase when closing 10 %, 40 %, and 60 % of the winding turns is, respectively, 21 %, 77 % and 89 %. At the same time, there is an increase in the amplitude of the first harmonic of the current of the damaged phase by 3.7 to 7.8 times. The obtained research results make it possible to improve relay protection systems for synchronous generators, namely protection against turn-to-turn circuits in stator windings without parallel branches.
... Unlike the Fourier transform, the drawback of wavelets and Hilbert-Huang transforms is their incompatibility with real-time analysis. Additionally, a detection technique using an analysis of the external field, provided by sensors positioned around the machine, using information fusion methods is proposed in [18][19][20][21], but these methods require an accurate knowledge of the external stray flux. ...
... where µ 0 = 4π10 −7 is the permeability of a vacuum approximately equal to that of the air, p s = l e s /5 is the stator fictive slot depth [18], r s d is the stator toothing ratio, and K s is the permeance rank. Where Fw,faulty is the winding function in the faulty state, and Nf is the number of faulty stator turns. ...
... the permeability of a vacuum approximately equal to that of the air, p s = l e s/5 is the stator fictive slot depth[18], s d r is the stator toothing ratio, and s K is the permeance rank. ...
Multiple factors and consequences may lead to a stator winding fault in an external rotor permanent magnet synchronous motor that can unleash a complete system shutdown and impair performance and motor reliability. This type of fault causes disturbances in operation if it is not recognized and detected in time, since it might lead to catastrophic consequences. In particular, an external rotor permanent magnet synchronous motor has disadvantages in terms of fault tolerance. Consequently, the distribution of the air-gap flux density will no longer be uniform, producing fault harmonics. However, a crucial step of diagnosis and controlling the system condition is to develop an accurate model of the machine with a lack of turns in the stator winding. This paper presents an analytical model of the stator winding unbalance fault represented by lack of turns. Here, mathematical approaches are used by introducing a stator winding parameter for the analytical modeling of the faulty machine. This model can be employed to determine the various quantities of the machine under different fault levels, including the magnetomotive force, the flux density in the air-gap, the flux generated by the stator winding, the stator inductances, and the electromagnetic torque. On this basis, a corresponding link between the fault level and its signature is established. The feasibility and efficiency of the analytical approach are validated by finite element analysis and experimental implementation.
Abstract This paper presents an equipment for monitoring synchronous generators condition through characteristics of the time derivative of the external magnetic field. The developed monitoring methodology allows the identification of established or incipient faults, by detecting changes in the magnetic signature of the synchronous generator. In this methodology, the measurement of signals outside the machine gives this equipment a non-invasive characteristic, allowing its monitoring without interfering or disturbing its operation. The developed system includes the specification of magnetic field sensors, signal measurement and processing equipment, as well as software for analysis and monitoring. The validation of the methodology used in this system was carried out through the analysis of experimental data, presenting efficient results in the detection of electrical and mechanical faults in synchronous generators of an experimental test bench and a hydroelectric power plant. As a result, the commercial specification of this equipment was obtained and two units were implemented in a hydroelectric power plant to monitor 305 MVA synchronous generators.
Condition monitoring of synchronous generators through non-invasive methods is widely requested by maintenance teams for not interfering the machine operation. Among the techniques used, external magnetic field monitoring is a recent strategy with great potential for detecting incipient faults. In this context, this paper proposes the application of a simple strategy with low computational cost to process data of external magnetic field time derivative signals for the purposes of condition monitoring and fault detection in synchronous machines. The information of interest is extracted from changes in the magnetic signature of the synchronous generator, obtained from frequency spectra of monitored signals using induction magnetic field sensors. The process forms a set of time series that reflects constructive and operational characteristics of the machine. The Shewhart control chart method is applied for anomaly detection in these time series, allowing the detection of changes in the machine magnetic signature. This method is employed in an algorithm for continuous condition monitoring of synchronous generators, presenting as output a global change indicator for the multivariable problem associated with magnetic signature monitoring. Correlation matrices are used to improve the algorithm response, filtering series with similar variation patterns associated with detected events. The proposed method is validated through tests on an experimental bench that allows the controlled imposition of faults in a synchronous generator. The proposed global change indicator allows the automatic detection of stator and rotor faults with the machine synchronized with the commercial power grid. The proposed methodology is also applied on data obtained from an equipment installed in a 305 MVA synchronous generator of a hydroelectric power plant where the evolution of an incipient fault, i.e., a mechanical vibration fault, has been detected.
