The Experts below are selected from a list of 318 Experts worldwide ranked by ideXlab platform
Xufeng Xu - One of the best experts on this subject based on the ideXlab platform.
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Impacts of Water-Tree Fault on Ferroresonance in Underground Cables
Journal of Power and Energy Engineering, 2017Co-Authors: Elham B. Makram, Xufeng XuAbstract:Nowadays, more and more electrical power is being distributed to customers by Underground Cables rather than overhead transmission lines due to their advantage of providing better protection in inclement weather. They also have significantly reduced electromagnetic field emission because of their copper shielding. But Underground Cables have larger capacitance than transmission lines per unit. Thus, ferroresonance is more likely to occur in distribution systems using Underground Cables. Moreover, soil humidity at a depth of one meter remains 100 percent for most of the year, a factor that risks the occurrence of water tree (WT) in Cables. Consequently, both ferroresonance and WT are prone to occur in Underground cable systems. The objective of this paper is to determine the relationship between ferroresonance and water tree. A test system was designed to simulate and analyze ferroresonance in a cable system caused by single-phase switch and water tree. Eight scenarios of water tree were compared in the simulation. There sponses of ferroresonance are presented in this paper and two common patterns are observed from the simulation results.
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A hybrid high frequency pulse and pattern recognition method for water tree detection in long distance Underground Cables
2015 IEEE Power & Energy Society General Meeting, 2015Co-Authors: Qi Chen, Elham Makram, Xufeng XuAbstract:The demand for wind energy has been on the rise. To satisfy this demand, power utilities have begun to construct an increasing number of wind generation facilities. Many of facilities are located in areas that require long distance Underground Cables connections to the grid. Maintaining these Cables requires techniques to identify and locate potential problems such as water tree. However, many traditional detection techniques are not designed for long Cables; therefore, new method must be developed to remotely and non-destructively locate and measure water tree development in long Underground Cables. By using a combination of high frequency pulse and pattern recognition, the new method can establish a system of benchmark frequencies corresponding to specific water tree capacitance values for a given piece cable. The new method works best for long Cables and small water tree capacitances. It supplements tradition water tree detection techniques, such as travelling wave and partial discharge.
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Capacitance of Water Tree Modeling in Underground Cables
Journal of Power and Energy Engineering, 2014Co-Authors: Qi Chen, Klaehn Burkes, Ramtin Hadidi, Elham Makram, Xufeng XuAbstract:Water Tree is a corrosion phenomenon in cross-link polyethylene (XLPE) insulation. It is com-monly found in Underground Cables. Water tree induced fault is difficult to detect due to its high impedance and difficult to model due to its random nature. In recent years, Underground Cables have become more popular in the power industry. They are resistant to environmental damage and has reduced space requirement. They are suitable to areas with high environment hazard or heavily populated areas where space is a constraining factor. As a result, studying and modeling the structure and effect of water tree become increasingly important. Since majority of the fault inducing water trees are vented trees which originated from the surface of the cable insulation, the mathematical model focuses on this particular type of water tree. To reduce the complexity of the model, the shape of the water tree afflicted region of the insulation is assumed to be ellipsoidal and the permittivity of the region is assumed to be linearly changing. Finite element analysis is used to analyze the water tree affected region. The resultant capacitance is calculated and com-pared with a physical model from Comsol. The result obtained using the proposed mathematical model and the result obtained using physical simulation through Comsol package agrees with each other. Hence, this method can be used to analyze the effect of water tree fault in large power sys-tems.
H.f. Bilgin - One of the best experts on this subject based on the ideXlab platform.
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power quality solutions for light rail public transportation systems fed by medium voltage Underground Cables
IEEE Transactions on Industry Applications, 2012Co-Authors: A. Terciyanli, A. Acik, A. Cetin, M. Ermis, I. Cadirci, C. Ermis, T. Demirci, H.f. BilginAbstract:In this paper, the combination of a thyristor-switched shunt reactor and a current source converter-based active power filter has been proposed for mitigation of power quality (PQ) problems of Light Rail public Transportation Systems (LRTSs) fed by long medium-voltage Underground Cables. A case study has been carried out on a typical LRTS to assess the performance of the proposed solution for both capacitive reactive power compensation of Underground Cables and harmonic filtering of 12-pulse catenary rectifiers. It has been shown by extensive field tests carried out that this solution meets the requirements satisfactorily, thus constituting a complete solution to the PQ problems of LRTS. Conventional PQ solutions have been also assessed, and the corresponding theoretical results are given in comparison with the proposed system.
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Power quality solutions for Light Rail public transportation systems fed by medium voltage Underground Cables
2010 IEEE Energy Conversion Congress and Exposition, 2010Co-Authors: A. Terciyanli, A. Acik, A. Cetin, M. Ermis, I. Cadirci, C. Ermis, T. Demirci, H.f. BilginAbstract:In this paper, the combination of a Thyristor Switched shunt Reactor (TSR) and a Current Source Converter (CSC) based Active Power Filter (APF) has been proposed for mitigation of power quality problems of Light Rail public Transportation Systems (LRTS) fed by long medium voltage Underground Cables. A case study has been carried out on a typical LRTS to assess the performance of the proposed solution for both capacitive reactive power compensation of Underground Cables and harmonic filtering of 12-pulse catenary rectifiers. It has been shown by extensive field tests carried out that this solution meets the requirements satisfactorily, thus constituting a complete solution to the power quality problems of LRTS. Conventional power quality solutions have also been assessed, and the corresponding theoretical results are given in comparison with the proposed system.
T.t. Nguyen - One of the best experts on this subject based on the ideXlab platform.
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Evaluation of modal transformation matrices for overhead transmission lines and Underground Cables by optimization method
IEEE Transactions on Power Delivery, 2002Co-Authors: T.t. Nguyen, H.y. ChanAbstract:The paper develops a numerical procedure based on constrained optimization for evaluating the modal transformation matrices of overhead transmission lines and Underground Cables. In the method, the eigenvalue-eigenvector equation is transformed into an objective function which is then minimized for finding eigenvalues and eigenvectors. The method developed avoids completely the problem of eigenvalue switching which causes the discontinuities of eigenvectors encountered in the QR-method. Initial values for starting the optimization at each frequency are the eigenvalues and eigenvectors evaluated at the preceding frequency. This technique leads to the set of smooth eigenvectors that define the modal transformation matrices. The form of the objective function derived in the paper for minimization together with the sequential quadratic programming technique guarantees that convergence to valid eigenvalues and eigenvectors is achieved. Using the method, transformation matrices for a wide range of frequency for representative double-circuit line and Underground cable are evaluated.
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evaluation of modal transformation matrices for overhead transmission lines and Underground Cables by optimization methods
IEEE Power & Energy Magazine, 2001Co-Authors: T.t. Nguyen, H.y. ChanAbstract:This article develops a numerical procedure based on constrained optimization for evaluating the modal transformation matrices of overhead transmission lines and Underground Cables. In the method, the eigenvalue-eigenvector equation is transformed into an objective function, which is then minimized for finding eigenvalues and eigenvectors. The developed method completely avoids the problem of eigenvalue switching, which causes the discontinuities of eigenvectors encountered in the QR method. Initial values for starting the optimization at each frequency are the eigenvalues and eigenvectors evaluated at the preceding frequency. This technique leads to the set of smooth eigenvectors that define the modal transformation matrices. The form of the objective function derived in the paper for minimization, together with the sequential quadratic programming technique, guarantees that convergence to valid eigenvalues and eigenvectors is achieved. Using the method, transformation matrices for a wide range of frequency for representative double-circuit line and Underground cable are evaluated.
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Earth-return path impedances of Underground Cables. II. Evaluations using neural networks
IEE Proceedings - Generation Transmission and Distribution, 1998Co-Authors: T.t. NguyenAbstract:For pt.II see ibid., vol.145, no.6, p.621-6 (1998). The aim of the paper is to train an array of neural networks to provide a procedure with high accuracy and low computing time requirement for evaluating the earth-return path impedances of Underground Cables. The training set required is formed by using a direct numerical integration method to evaluate the infinite integrals in the earth-return path formulations. The training is extensive but, once completed, it is valid for any cable configuration as it arises. The training leads to a universal set of weighting coefficients for an array of networks each of which has three input nodes, one output node and two hidden layers. Set up with these coefficients, the computing time requirements in calculating sets of series-path parameters for Underground Cables is reduced by a factor of about 1000 from that using a direct numerical evaluation of infinite integrals.
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Earth-return path impedances of Underground Cables. I. Numerical integration of infinite integrals
IEE Proceedings - Generation Transmission and Distribution, 1998Co-Authors: T.t. NguyenAbstract:Although it is generally acknowledged that there is a need to closely formulate the earth-return path impedances of Underground Cables, research published so far has mainly concentrated on developing approximate formulations, especially for the infinite integrals which arise. Instead of seeking approximations, the paper develops a rigorous method based on direct numerical integration to evaluate the infinite integrals of Underground cable earth-return path impedances. The method has immediate practical use in Underground cable parameter calculations. It also provides a benchmark by which the accuracy of any proposed approximate method can be assessed. Further, the method can be used to provide training data by means of which infinite integrals can be evaluated using an array of neural networks.
Tarlochan S. Sidhu - One of the best experts on this subject based on the ideXlab platform.
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Fault location method based on single-end measurements for Underground Cables
IEEE Transactions on Power Delivery, 2011Co-Authors: Zhihan Xu, Tarlochan S. SidhuAbstract:The fault location in Underground Cables is characterized as the technical difficulties due to complexities in Cables. Based on the direct circuit analysis, a fault location algorithm for Underground Cables with no laterals is presented in this paper. The single-end phasor measurements, including the voltages and currents sampled in the substation side, are utilized to locate the single phase faults in the typical single-conductor cross-linked polyethylene (XLPE) Cables rated at the medium voltage (MV) levels. The distinctive cable characteristics are considered, such as relatively large capacitance, effects of sheaths and sheath bonding methods. The different fault scenarios are taken into account as well. The effect of changes of cable parameters and application of static response load model are also investigated. The simulation studies demonstrate the proposed algorithm can achieve the high accuracy under various system and fault conditions.
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Detection of Incipient Faults in Distribution Underground Cables
IEEE Transactions on Power Delivery, 2010Co-Authors: Tarlochan S. Sidhu, Zhihan XuAbstract:The incipient faults in Underground Cables are largely caused by voids in cable insulations or defects in splices or other accessories. This type of fault would repeatedly occur and subsequently develop to a permanent fault sooner or later after its first occurrence. Two algorithms are presented to detect and classify the incipient faults in Underground Cables at the distribution voltage levels. Based on the methodology of wavelet analysis, one algorithm is to detect the fault-induced transients, and therefore identify the incipient faults. Based on the analysis of the superimposed fault current and negative sequence current in the time domain, the other algorithm is particularly suitable to detect the single-line-to-ground (SLG) incipient faults, which are mostly occurring in Underground Cables. Both methods are designed to be applied in real systems. Hence, to verify the effectiveness and functionalities of the proposed schemes, different fault conditions, various system configurations, and real field cases are examined and other transients caused by permanent fault, capacitor switching, load changing, etc., are studied as well.
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Detection and classification of incipient faults in Underground Cables in distribution systems
2009 Canadian Conference on Electrical and Computer Engineering, 2009Co-Authors: Tarlochan S. Sidhu, Zhihan XuAbstract:The incipient faults in Underground Cables are largely caused by voids in cable insulations or defects in splices or other accessories. This type of fault would repeatedly occur and subsequently develop to a permanent fault sooner or later after its first occurrence. Based on the methodology of wavelet analysis, a method is presented to detect and classify the incipient faults in Underground Cables at the distribution voltage level. The proposed method is designed to be possibly applied in real systems. Therefore, different fault conditions and system configurations are examined, and other transients caused by permanent fault, capacitor switching, load changing, etc., can also be discriminated.
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CCECE - Detection and classification of incipient faults in Underground Cables in distribution systems
2009 Canadian Conference on Electrical and Computer Engineering, 2009Co-Authors: Tarlochan S. Sidhu, Zhihan XuAbstract:The incipient faults in Underground Cables are largely caused by voids in cable insulations or defects in splices or other accessories. This type of fault would repeatedly occur and subsequently develop to a permanent fault sooner or later after its first occurrence. Based on the methodology of wavelet analysis, a method is presented to detect and classify the incipient faults in Underground Cables at the distribution voltage level. The proposed method is designed to be possibly applied in real systems. Therefore, different fault conditions and system configurations are examined, and other transients caused by permanent fault, capacitor switching, load changing, etc., can also be discriminated.
Zhihan Xu - One of the best experts on this subject based on the ideXlab platform.
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Fault location method based on single-end measurements for Underground Cables
IEEE Transactions on Power Delivery, 2011Co-Authors: Zhihan Xu, Tarlochan S. SidhuAbstract:The fault location in Underground Cables is characterized as the technical difficulties due to complexities in Cables. Based on the direct circuit analysis, a fault location algorithm for Underground Cables with no laterals is presented in this paper. The single-end phasor measurements, including the voltages and currents sampled in the substation side, are utilized to locate the single phase faults in the typical single-conductor cross-linked polyethylene (XLPE) Cables rated at the medium voltage (MV) levels. The distinctive cable characteristics are considered, such as relatively large capacitance, effects of sheaths and sheath bonding methods. The different fault scenarios are taken into account as well. The effect of changes of cable parameters and application of static response load model are also investigated. The simulation studies demonstrate the proposed algorithm can achieve the high accuracy under various system and fault conditions.
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Detection of Incipient Faults in Distribution Underground Cables
IEEE Transactions on Power Delivery, 2010Co-Authors: Tarlochan S. Sidhu, Zhihan XuAbstract:The incipient faults in Underground Cables are largely caused by voids in cable insulations or defects in splices or other accessories. This type of fault would repeatedly occur and subsequently develop to a permanent fault sooner or later after its first occurrence. Two algorithms are presented to detect and classify the incipient faults in Underground Cables at the distribution voltage levels. Based on the methodology of wavelet analysis, one algorithm is to detect the fault-induced transients, and therefore identify the incipient faults. Based on the analysis of the superimposed fault current and negative sequence current in the time domain, the other algorithm is particularly suitable to detect the single-line-to-ground (SLG) incipient faults, which are mostly occurring in Underground Cables. Both methods are designed to be applied in real systems. Hence, to verify the effectiveness and functionalities of the proposed schemes, different fault conditions, various system configurations, and real field cases are examined and other transients caused by permanent fault, capacitor switching, load changing, etc., are studied as well.
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Detection and classification of incipient faults in Underground Cables in distribution systems
2009 Canadian Conference on Electrical and Computer Engineering, 2009Co-Authors: Tarlochan S. Sidhu, Zhihan XuAbstract:The incipient faults in Underground Cables are largely caused by voids in cable insulations or defects in splices or other accessories. This type of fault would repeatedly occur and subsequently develop to a permanent fault sooner or later after its first occurrence. Based on the methodology of wavelet analysis, a method is presented to detect and classify the incipient faults in Underground Cables at the distribution voltage level. The proposed method is designed to be possibly applied in real systems. Therefore, different fault conditions and system configurations are examined, and other transients caused by permanent fault, capacitor switching, load changing, etc., can also be discriminated.
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CCECE - Detection and classification of incipient faults in Underground Cables in distribution systems
2009 Canadian Conference on Electrical and Computer Engineering, 2009Co-Authors: Tarlochan S. Sidhu, Zhihan XuAbstract:The incipient faults in Underground Cables are largely caused by voids in cable insulations or defects in splices or other accessories. This type of fault would repeatedly occur and subsequently develop to a permanent fault sooner or later after its first occurrence. Based on the methodology of wavelet analysis, a method is presented to detect and classify the incipient faults in Underground Cables at the distribution voltage level. The proposed method is designed to be possibly applied in real systems. Therefore, different fault conditions and system configurations are examined, and other transients caused by permanent fault, capacitor switching, load changing, etc., can also be discriminated.
