When, in a coal mine distribution network whose neutral point is grounded by an arc suppression coil (ASC), a fault occurs in the ASC, compensation cannot be properly realized. Furthermore, it can damage the safe and ...When, in a coal mine distribution network whose neutral point is grounded by an arc suppression coil (ASC), a fault occurs in the ASC, compensation cannot be properly realized. Furthermore, it can damage the safe and reliable run of the network. We first introduce a three-phase five-column arc suppression coil (TPFCASC) and discuss its autotracking compensation theory. Then we compare the single phase to ground fault of the coal mine distribution network with an open phase fault at the TPFCASC using the Thévenin theory, the symmetrical-component method and the complex sequence network respectively. The results show that, in both types of faults, zero-sequence voltage of the network will appear and the maximum magnitude of this zero-sequence voltage is different in both faults. Based on this situation, a protection for the open phase fault at the TPFCASC should be estab-lished.展开更多
Half-wavelength AC transmission(HWACT) is an ultra-long distance AC transmission technology, whose electrical distance is close to half-wavelength at the system power frequency. It is very important for the constructi...Half-wavelength AC transmission(HWACT) is an ultra-long distance AC transmission technology, whose electrical distance is close to half-wavelength at the system power frequency. It is very important for the construction and operation of HWACT to analyze its fault features and corresponding protection technology. In this paper, the steady-state voltage and current characteristics of the bus bar and fault point and the steady-state overvoltage distribution along the line will be analyzed when a three-phase symmetrical short-circuit fault occurs on an HWACT line. On this basis, the threephase fault characteristics for longer transmission lines are also studied.展开更多
The vibration signals of machinery with various faults often show clear nonlinear characteristics.Currently,fractal dimension analysis as the common useful method for nonlinear signal analysis,is a kind of single frac...The vibration signals of machinery with various faults often show clear nonlinear characteristics.Currently,fractal dimension analysis as the common useful method for nonlinear signal analysis,is a kind of single fractal form,which only reflects the overall irregularity of signals,but cannot describe its local scaling properties.For comprehensive revealing of internal properties,a combinatorial method based on band-phase-randomized（BPR） surrogate data and multifractal is introduced.BPR surrogate data method is effective to eliminate nonlinearity in specified frequency band for a fault signal,which can be utilized to detect nonlinear degree in whole fault signal by nonlinear titration method,and the overall nonlinear distribution of fault signal is displayed in nonlinear characteristic curve that can be used to analyze the fault signal qualitatively.Then multifractal theory as a quantitative analysis method is used to describe geometrical characteristics and local scaling properties,and asymmetry coefficient of multifractal spectrum and multifractal entropy for fault signals are extracted as new criterions to diagnose machinery faults.Several typical faults include rotor misalignment,transversal crack,and static-dynamic rubbing fault are analyzed,and the results indicate that those faults can be distinguished by the proposed method effectively,which provides a qualitative and quantitative analysis way in the field of machinery fault diagnosis.展开更多
The soft fault induced by parameter variation is one of the most challenging problems in the domain of fault diagnosis for analog circuits.A new fault location and parameter prediction approach for soft-faults diagnos...The soft fault induced by parameter variation is one of the most challenging problems in the domain of fault diagnosis for analog circuits.A new fault location and parameter prediction approach for soft-faults diagnosis in analog circuits is presented in this paper.The proposed method extracts the original signals from the output terminals of the circuits under test（CUT） by a data acquisition board.Firstly,the phase deviation value between fault-free and faulty conditions is obtained by fitting the sampling sequence with a sine curve.Secondly,the sampling sequence is organized into a square matrix and the spectral radius of this matrix is obtained.Thirdly,the smallest error of the spectral radius and the corresponding component value are obtained through comparing the spectral radius and phase deviation value with the trend curves of them,respectively,which are calculated from the simulation data.Finally,the fault location is completed by using the smallest error,and the corresponding component value is the parameter identification result.Both simulated and experimental results show the effectiveness of the proposed approach.It is particularly suitable for the fault location and parameter identification for analog integrated circuits.展开更多
The aim of the present paper is to obtain the two-dimensional deformation of a two-phase elastic medium consisting of half-spaces of different ri- gidities in welded contact due to a buried long strike-slip fault. The...The aim of the present paper is to obtain the two-dimensional deformation of a two-phase elastic medium consisting of half-spaces of different ri- gidities in welded contact due to a buried long strike-slip fault. The solution is valid for arbitrary values of the fault-depth and the dip angle. The effect of fault-depth on the displacement and stress fields for different values of dip angle has been studied numerically. It is found that the displacement field varies significantly for a buried fault from the corresponding displacement field for an interface-breaking fault. The contour maps showing the stress field for various dip angles for buried and interface-breaking fault have been plotted. It has been observed that the stress field varies significantly for a buried fault from the corresponding stress field for an interface-breaking fault.展开更多
针对现有配电网有源电压消弧方法未充分考虑线路电压降落以及分布式电源接入的影响,发生单相接地故障时无法保证故障点电压为0,存在无法可靠消弧的问题,提出了一种考虑分布式电源接入的配电网有源电压消弧技术。首先,在接入分布式电源...针对现有配电网有源电压消弧方法未充分考虑线路电压降落以及分布式电源接入的影响,发生单相接地故障时无法保证故障点电压为0,存在无法可靠消弧的问题,提出了一种考虑分布式电源接入的配电网有源电压消弧技术。首先,在接入分布式电源的基础上,考虑线路的电压降落,推导消弧电压理论计算公式,提出改进有源电压消弧方法。其次,提出一种基于馈线终端设备(feeder terminal unit, FTU)量测数据的数据驱动测距方法,能够在故障发生后准确计算出故障距离,为消弧线圈的控制提供数据。最后,通过仿真证明所提方法相较于传统有源电压消弧方法,能够更好地控制故障点电压为0。展开更多
选相选线是配电网单相接地故障有效治理的关键环节。针对现有选相选线方法在高阻接地故障时辨识能力不足、适应性差的问题,该文提出一种基于特征电流变化量的配电网高阻接地故障主动选相选线方法。首先,分析了单相接地故障前后零序电压...选相选线是配电网单相接地故障有效治理的关键环节。针对现有选相选线方法在高阻接地故障时辨识能力不足、适应性差的问题,该文提出一种基于特征电流变化量的配电网高阻接地故障主动选相选线方法。首先,分析了单相接地故障前后零序电压特征分量的变化规律及其响应机理;其次,通过对比健全相与故障相特征电流变化量辐角主值(characteristic current variation principle value,CCV-PV)的特性差异,构建了基于母线CCV-PV的故障主动选相方法;再次,通过比较健全馈线与故障馈线的CCV-PV特性差异,构建了基于馈线CCV-PV故障主动选线方法。理论分析和仿真验证表明:仅需有源消弧装置注入特征电流即可实现接地故障的主动选相和选线,并且所提方法在高阻接地故障、三相零序不对称、非同步采样等复杂场景下均具有较高的灵敏度。展开更多
文摘When, in a coal mine distribution network whose neutral point is grounded by an arc suppression coil (ASC), a fault occurs in the ASC, compensation cannot be properly realized. Furthermore, it can damage the safe and reliable run of the network. We first introduce a three-phase five-column arc suppression coil (TPFCASC) and discuss its autotracking compensation theory. Then we compare the single phase to ground fault of the coal mine distribution network with an open phase fault at the TPFCASC using the Thévenin theory, the symmetrical-component method and the complex sequence network respectively. The results show that, in both types of faults, zero-sequence voltage of the network will appear and the maximum magnitude of this zero-sequence voltage is different in both faults. Based on this situation, a protection for the open phase fault at the TPFCASC should be estab-lished.
基金supported by National Key Research and Development Program of China(2016YFB0900100)
文摘Half-wavelength AC transmission(HWACT) is an ultra-long distance AC transmission technology, whose electrical distance is close to half-wavelength at the system power frequency. It is very important for the construction and operation of HWACT to analyze its fault features and corresponding protection technology. In this paper, the steady-state voltage and current characteristics of the bus bar and fault point and the steady-state overvoltage distribution along the line will be analyzed when a three-phase symmetrical short-circuit fault occurs on an HWACT line. On this basis, the threephase fault characteristics for longer transmission lines are also studied.
基金supported by National Natural Science Foundation of China (Grant No. 61077071,Grant No. 51075349)Hebei Provincial Natural Science Foundation of China (Grant No. F2011203207)
文摘The vibration signals of machinery with various faults often show clear nonlinear characteristics.Currently,fractal dimension analysis as the common useful method for nonlinear signal analysis,is a kind of single fractal form,which only reflects the overall irregularity of signals,but cannot describe its local scaling properties.For comprehensive revealing of internal properties,a combinatorial method based on band-phase-randomized（BPR） surrogate data and multifractal is introduced.BPR surrogate data method is effective to eliminate nonlinearity in specified frequency band for a fault signal,which can be utilized to detect nonlinear degree in whole fault signal by nonlinear titration method,and the overall nonlinear distribution of fault signal is displayed in nonlinear characteristic curve that can be used to analyze the fault signal qualitatively.Then multifractal theory as a quantitative analysis method is used to describe geometrical characteristics and local scaling properties,and asymmetry coefficient of multifractal spectrum and multifractal entropy for fault signals are extracted as new criterions to diagnose machinery faults.Several typical faults include rotor misalignment,transversal crack,and static-dynamic rubbing fault are analyzed,and the results indicate that those faults can be distinguished by the proposed method effectively,which provides a qualitative and quantitative analysis way in the field of machinery fault diagnosis.
基金supported by the National Natural Science Foundation of China under Grant No.61371049
文摘The soft fault induced by parameter variation is one of the most challenging problems in the domain of fault diagnosis for analog circuits.A new fault location and parameter prediction approach for soft-faults diagnosis in analog circuits is presented in this paper.The proposed method extracts the original signals from the output terminals of the circuits under test（CUT） by a data acquisition board.Firstly,the phase deviation value between fault-free and faulty conditions is obtained by fitting the sampling sequence with a sine curve.Secondly,the sampling sequence is organized into a square matrix and the spectral radius of this matrix is obtained.Thirdly,the smallest error of the spectral radius and the corresponding component value are obtained through comparing the spectral radius and phase deviation value with the trend curves of them,respectively,which are calculated from the simulation data.Finally,the fault location is completed by using the smallest error,and the corresponding component value is the parameter identification result.Both simulated and experimental results show the effectiveness of the proposed approach.It is particularly suitable for the fault location and parameter identification for analog integrated circuits.
文摘The aim of the present paper is to obtain the two-dimensional deformation of a two-phase elastic medium consisting of half-spaces of different ri- gidities in welded contact due to a buried long strike-slip fault. The solution is valid for arbitrary values of the fault-depth and the dip angle. The effect of fault-depth on the displacement and stress fields for different values of dip angle has been studied numerically. It is found that the displacement field varies significantly for a buried fault from the corresponding displacement field for an interface-breaking fault. The contour maps showing the stress field for various dip angles for buried and interface-breaking fault have been plotted. It has been observed that the stress field varies significantly for a buried fault from the corresponding stress field for an interface-breaking fault.
文摘针对现有配电网有源电压消弧方法未充分考虑线路电压降落以及分布式电源接入的影响,发生单相接地故障时无法保证故障点电压为0,存在无法可靠消弧的问题,提出了一种考虑分布式电源接入的配电网有源电压消弧技术。首先,在接入分布式电源的基础上,考虑线路的电压降落,推导消弧电压理论计算公式,提出改进有源电压消弧方法。其次,提出一种基于馈线终端设备(feeder terminal unit, FTU)量测数据的数据驱动测距方法,能够在故障发生后准确计算出故障距离,为消弧线圈的控制提供数据。最后,通过仿真证明所提方法相较于传统有源电压消弧方法,能够更好地控制故障点电压为0。
文摘选相选线是配电网单相接地故障有效治理的关键环节。针对现有选相选线方法在高阻接地故障时辨识能力不足、适应性差的问题,该文提出一种基于特征电流变化量的配电网高阻接地故障主动选相选线方法。首先,分析了单相接地故障前后零序电压特征分量的变化规律及其响应机理;其次,通过对比健全相与故障相特征电流变化量辐角主值(characteristic current variation principle value,CCV-PV)的特性差异,构建了基于母线CCV-PV的故障主动选相方法;再次,通过比较健全馈线与故障馈线的CCV-PV特性差异,构建了基于馈线CCV-PV故障主动选线方法。理论分析和仿真验证表明:仅需有源消弧装置注入特征电流即可实现接地故障的主动选相和选线,并且所提方法在高阻接地故障、三相零序不对称、非同步采样等复杂场景下均具有较高的灵敏度。
