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Foremost systems of electrical energy production are based on three-phases synchronous generators. In this work we are going to propose an efficient diagnosis technique, based on the use of a low-cost sensor, for the online detection of a transient abrupt drop in the drive speed system. Tests have been conducted on a four-pole brushless alternator driven by a DC shunt motor. Through conventional time-frequency...
Lightning stroke on line may lead to mal-operation of relay protection, possibly invades substation, and further results in over-voltage of system. A S-transform based method for monitoring and identifying lightning inrush in substations is proposed in this paper. By monitoring busbar voltage signals in real-time, the waveform characteristics of transient voltage signals in both time domain and frequency...
In this paper, high-order fault-related current harmonics are used for the diagnosis and discrimination between two different faults in induction machines: rotor asymmetries and mixed eccentricities, both when only these faults are simultaneously present in the machine and when they are combined with other non-fault related phenomena. The idea is to track the evolutions of both the high-order fault-related...
This paper studies the transient stability of the micro-grid supplied by multiple distributed generations, which are interfaced by synchronous generator and inverters. The study is performed by DIgSILENT Power Factory 14.0 and the IEEE 37-node distribution system is used for simulations. The three-phase-to-ground short-circuit fault is applied when doing the following work. The transient behaviors...
A novel application of Hilbert-Huang transform method to fault diagnosis of gear crack is presented. The methodology developed in this paper decomposes the original times series data in intrinsic oscillation modes, using the empirical mode decomposition. Then the Hilbert transform is applied to each intrinsic mode function. Therefore, the time-frequency distribution is obtained. The basic method is...
In this paper a recently developed induction motors diagnosis methodology is applied to detect mixed eccentricity in Inverter-Fed Induction Motors (IFIMs). The classic FFT method can not be applied when the stator current captured is not in steady state (which is common in IFIMs). The approach is based on obtaining a 2D time - frequency plot representing the time - frequency evolution of the main...
The objective of this paper is to introduce Newland Harmonic wavelets and Richman -Moorman (2000) sample entropy are applied to detect singularity signal on worn tool. Because some weak vibration signals contained strong noises are very important for fault forecast. Based on harmonic wavelet mesh plot of the vibration signals, we can induce contours of the mesh map with log space, then, we offer the...
This paper proposed a novel identification method for voltage sags (dips) based on Hilbert-Huang transform (HHT). Different voltage sag has distinct characters of fault time, three-phase amplitude and harmonics. And HHT is an excellent time-frequency representation and very suitable for feature extraction of voltage sags. The time-frequency absolute values of the instantaneous frequency differential...
Considering the fault characteristic of rotating machinery, a novel approach was proposed by using harmonic wavelet filtering. Based on the fine refinement function of harmonic wavelet, the characteristic frequency components and other components were decomposed to independent frequency bands, without any overlapping or leaking. Then the characteristic frequency component would be extracted by the...
In order to extract impulsive feature of fault signal, a novel approach was proposed by using harmonic wavelet package. With this method, the signal could be decomposed into any frequency band, and then the interested frequency band could be extracted and reconstructed in time domain, so the impulsive feature could be extracted from rubbing fault signal. Simulation and practical example show the good...
The paper introduces a monitoring and diagnostic technique for the detection of incipient stator electrical faults in Doubly Fed Induction Machine (DFIM) for wind power systems. Operating in aggressive environments, the detection of anomalies at an incipient stage is crucial to decide about the operating continuity of the machines. Discrete Wavelet Transform (DWT) is used to detect stator faults under...
In this paper a new methodology of transient motor current signature analysis (TMCSA) is proposed. The approach consists on obtaining a 2D time frequency plot representing the time-frequency evolution of all the harmonics present on an electric machine transient current. Identifying characteristic patterns in the time-frequency plane, produced by some of the fault related components, permits the machine...
Variable speed drives are becoming the method of choice for powering AC motors in many industrial applications. They allow for flexible speed control, substantial energy savings, and reduced stress during motor start-up, all of which lead to lower lifecycle costs for the shaft line. Modern drives, in order to perform their controlling function, are equipped with sensors, hardware and software to measure...
The diagnosis of rotor asymmetries in induction machines through the use of methods based on the study of the startup current has become an issue of special interest. These techniques may provide, in certain situations (unbalance supply voltages, load torque oscillations...), substantial advantages in comparison with the classical method, based on the Fourier spectrum of the steady-state current....
According to the fault of rotor bar breakage, the paper put forward a diagnosis method to extract the fault characteristic signal in stator current, by signal processing with Fourier Transform and wavelet transform theory. To validate its feasibility, simulation and experiment on frequency converter sets are made, and the results show that the given method perform well in the fault diagnosis application.
The paper introduces a monitoring and diagnostic technique for the detection of incipient stator electrical faults in doubly fed induction generators (DFIGs) for wind power systems. Depending on wind speed, the induction machine operates continuously in non stationary conditions. In this context, traditional Fourier Analysis fails to discriminate between healthy and abnormal stator operating conditions...
This paper presents a new algorithm for transformer differential protection, based on pattern recognition of the instantaneous differential currents. A decision logic by wavelet Transform has been devised using extracted feature from differential currents due to internal fault and inrush currents. In this logic, diagnosis criterion is based on time difference of amplitudes of wavelet coefficients...
The present work shows that the Wigner-Ville and Choi-Williams distributions are useful to determine the proper operation of rotating axes driven by motors and speed controllers. The bearing diagnosis obtained by analyzing real sound samples using phase-array ultrasonic technology will be discussed to highlight the importance of the proposed tools for industrial machinery monitoring.
It is described that Fast Fourier Transform (FFT) implementation in floating-point DSP TMS320VC33. The result indicate that assemble language is more suitable for implementing the complicated algorithms than c language, validates the correctness of FFT algorithms, indicates that the implement of FFT with DSP own antitone indirect addressing is very convenient, the real-time performance is also very...
This paper shows a new polynomial Kernel (a non-Gaussian window) suitable for the implementation of phase corrected wavelet transform, in a recursive manner, which the target is to track harmonics and inter-harmonics and achieve acceleration in the disturbances detection process and help the waveform characterization in power quality analyzers that must be in compliance at the same time with the power...
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