Jiancheng Song

Nonlinear modeling of switched reluctance machine

As the static magnetic characteristic of switched reluctance machine(SRM) is nonlinear and its accurate mathematical modeling is difficult to set up, the least squares support vector machine method has been used to the nonlinear modeling of switched reluctance machine. For an 8/6 SRM prototype, The flux-linkage characteristic and the torque-angle characteristic of has been obtained by experimental method, and the model of switched reluctance machine based on the least squares support vector machine has been build and its drive system has been simulated. The experimental results show that the simulated current waveform is in accordance with the experimental one, which verify the correctness of modeling method in this paper.

Breakdown performance and electrical aging life model of EPR used in coal mining cables

Ethylene Propylene Rubber (EPR) with excellent dielectric properties has been widely used as cable insulation specially to be used where cables need to be moved frequently, such as in coal mine. Usually, theses cables will be bending excessively, coupled with the electric stress and thermal stress, the aging of the insulation tend to accelerate and the strength of insulation could decrease, with the time prolonging, breakdown may be happened. So, it is necessary to make research on the breakdown characteristics of EPR. To understand the breakdown performance, a step-stress test method is used in the accelerated life tests of EPR and WEIBULL distribution is used to analyze the test dates. Finally, based on inverse power life model, the voltage life index of EPR have been obtained. Finally, the electrical aging life model of EPR have be obtained. Research on the breakdown characteristics and the voltage life index of EPR is significance for insulation structure design and residual life assessment.

Characteristic analysis of asynchronous motor fault signal based on wavelet packet decomposition

This paper presents characteristic frequency analysis of asynchronous motor fault signal based on wavelet packet decomposition. Asynchronous motors current and vibration signals are acquisition objects, Fault diagnosis is based on frequency information contained in motors signals. The wavelet packet decomposition (WPD) method is applied to extract their characteristic frequency, and then its necessary to ascertain WPD layers according to signal sampling frequency and the requirement of frequency resolution. A method is put forward, which characteristic frequency is located quickly to node in the WPD layer. It may promote the application of wavelet packet analysis method in motor fault diagnosis system.

Simulation for Switched Reluctance Drive Based on the Measured Flux Linkage Characteristics

The static characteristics of a 3-phase 12/8 switched reluctance motor (SRM) are measured by indirect method. Based on the measured flux linkage characteristics, the nonlinear mathematical model of SRM is established in Matlab/Simulink environment; the control strategy and algorithm of switched reluctance drive (SRD) are developed. The simulation results are in accord with the results by finite-element analysis and it reflect the operating characteristics of SRM. In addition, the results will be of reference value in the further research and development of SRD.

Influence of thermal aging on AC leakage current in XLPE insulation

Cross-linked polyethylene (XLPE) has been widely used as cable insulation material because of its excellent dielectric properties, thermal stability and solvent resistance. To understand the influence of thermal aging on AC leakage current in XLPE insulation, all XLPE specimens were aged in oven in temperature range from 120 °C to 150 °C, and a series of tests were conducted on these XLPE specimens in different aging stages to measure the characteristic parameters, such as complex permittivity, leakage current and complex dielectric modulus. In the experiments, the effects of thermal aging, temperature and frequency on the AC leakage current in XLPE insulation were studied by analyzing complex dielectric constant and dielectric relaxation modulus spectrum, the change of relaxation peak and activation energy. It has been found that the active part of leakage current increases sharply with the increase of aging degree, and the test temperature and frequency have an influence on AC leakage current but the in...

AC flashover performance and polarization current of ethylene propylene rubber under different temperature

In order to evaluate the influence of AC flashover on the insulation performance of Ethylene Propylene Rubber (EPR) at different temperature, the characteristic indicators were studied, based on the polarization and depolarization current (PDC). In the paper, the partial discharge inception and extinction voltage and the flashover voltage were firstly measured under AC voltage at the ambient temperature and 90 °C, respectively. Before the occurrence of flashover, the partial discharge distribution was discussed under different voltage amplitude. Then, PDC was measured after the flashover test. The fit lines of PDC were drawn through the empirical formula for explaining the mechanism of AC flashover over the surface of EPR.

Fault pattern recognition method for the high voltage circuit breaker based on the incremental learning algorithms for SVM

In order to recognize faults of the high voltage circuit breaker (HVCB) in the whole fault state space precisely and minimize the impact of the lack of fault data on the accuracy of fault recognition, a method of fault recognition was proposed based on the incremental learning algorithm for SVM. Firstly, the incremental learning algorithm for SVM was analyzed theoretically, and the state monitoring variables were determined by the current signal and voltage signal of control unit and the vibration signal of the switching for HVCB. Based on the fault mechanism, the feature extraction method for the monitoring variables was proposed. Secondly, four common faults, including the spring loosening, the core jamming, the coil aging and the abnormal electrical power supply, were simulated. Then the fault feature was extracted, and the fault data samples as well as the incremental learning data samples were established. After training the feature variables based on the incremental learning algorithms for SVM, the fault recognition model was acquired and its accuracy was validated through exerting the new fault features into the model. Finally, it is shown that the incremental learning algorithms for SVM can be used to recognize the faults of HVCB effectively, and its recognition accuracy can be improved by continuous learning of the new samples.

Effect of surface electrical tracking of ethylene propylene rubber on return voltage

Electrical tracking is one of the main reasons for the deterioration of insulation surface. According to the problem of the surface electrical tracking erosion of insulation used in the high-voltage mining cables, the Ethylene Propylene Rubber samples with different electrical tracking development stage were selected in the paper. The relationship between the surface electrical tracking erosion degree of Ethylene Propylene Rubber and return voltage were analyzed. Characteristic parameters, which including the maximum value of return voltage, the constant of dominant time constant and the initial slope of return voltage were calculated based on the return voltage curves. It has been found that the maximum value of return voltage, the constant of dominant time and the initial slope of return voltage are closely related to the electrical tracking development stage. The constant of dominant time is significantly reduced with the increasing of the surface electrical tracking erosion degree. Research results demonstrate that the severity degree of electrical tracking erosion can be discriminated with Return Voltage.

Characteristics of flashover and discharge over the surface of Ethylene Propylene Rubber

Defects of Ethylene Propylene Rubber (EPR)cablesare the source of partial discharges, which will lead to insulation degradation. The flashover voltage and discharge properties along the surface of EPR were measuredunder edge to edge electrode, needle to edge electrode and rod to ring electrode. Experimental results show that the flashover voltage magnitude over EPR depends on the type of voltage. The inception voltage magnitude of surface dischargerelates to the formation and development of electron avalanche and streamer. The surface discharge distributions in different electrode configuration are different. Moreover, the applied voltage drops to low values when the spark discharge orarc discharge is taking place.

Partial discharge properties of electrical trees in XLPE

Cross-linked polyethylene is widely used as the insulation of power cables due to its superior insulation and mechanical properties. Electrical trees is one of the main reasons for the breakdown of cable insulation. In order to explore the growth process and partial discharge characteristics of electrical trees in cross-linked polyethylene, cuboid samples taken from a commercial cable and a needle-plane electrodes were used to develop electrical trees. In this paper, a real-time observation system was designed to record the growth picture of electrical trees and a partial discharge measurement system was used to obtain the partial discharge patterns during treeing. The experimental results show that the structure of electrical tree varied in stages. There are four stages during the growth of electrical trees, namely, initiation stage, slow growth stage, rapid growth stage and sustained growth stage. The outline of PD distribution patterns is bimodal shape. During treeing, the numbers of PDs in the two cycle are almost equal.