The Experts below are selected from a list of 1323 Experts worldwide ranked by ideXlab platform
Shen Quanrong - One of the best experts on this subject based on the ideXlab platform.
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Study on Issues of Generator Rotor Earth Fault Protection
Automation of electric power systems, 2008Co-Authors: Shen QuanrongAbstract:This paper analyzes the influences of shaft voltage absorbing circuit and brush touching resistance on the performance of generator rotor Earth Fault Protection. Some countermeasures and advices are presented. Prolonging period of electric switches and injected square voltage is suggested to eliminate the influence of shaft voltage. It is necessary for rotor Earth Fault Protection to keep good-touching of grounding brush and rotor shaft. Rotor Earth Fault Protection configuration of revolving excitation generator is investigated subsequently, and periodical detecting mode is commended.
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Generator Stator and Rotor Earth Fault Protection Scheme of Ultra-supercritical Generating Unit
Automation of electric power systems, 2008Co-Authors: Shen QuanrongAbstract:This paper analyzes the shortage of conventional generator stator and rotor Earth Fault Protection applied to ultra-supercritical generating unit.A novel stator and rotor Earth Fault Protection scheme is proposed subsequently,and voltage injection type stator and rotor Earth Fault Protection are commended,which are immune to the operating condition of generator.
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field application and analysis of the stator Earth Fault Protection with voltage injection for large sized generator
Automation of electric power systems, 2007Co-Authors: Shen QuanrongAbstract:More and more large-sized generators are installed 100% stator Earth Fault Protection with low-frequency alternating-voltage injection.The field adjustment methods of the voltage injection scheme against the stator Earth Fault Protection are summarized and the experimental results are given.The equipment measuring accuracy(relative error is not greater than ±5%)of the Earth Fault resistors is verified by the experimental results.Moreover,some suggestions are given by analyzing a two-point Earth Fault in potential transformers circuit,which can cause stator Earth Fault Protection warning.
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study on stator Earth Fault Protection of generator connected as expanding unit
Automation of electric power systems, 2007Co-Authors: Shen QuanrongAbstract:A novel selective stator Earth Fault Protection based on zero-sequence direction element is proposed, which can overcome the shortage of stator Earth Fault Protection applied to generator connected as expanding unit. In the proposed algorithm, the zero-sequence direction criterion is calculated with zero-sequence current of generator terminal, the secondary current of neutral Earthing transformer and zero-sequence voltage of generator, and its operating border can be set flexibly. The presented criterion can differentiate between a network Earth Fault and a generator stator Earth Fault exactly, which has been realized in digital generator Protection. Experiment results show its validity and reliability.
Matti Lehtonen - One of the best experts on this subject based on the ideXlab platform.
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bayesian selectivity technique for Earth Fault Protection in medium voltage networks
IEEE Transactions on Power Delivery, 2010Co-Authors: Nagy I Elkalashy, Abdelsalam Elhaffar, Tamer A Kawady, Naser Tarhuni, Matti LehtonenAbstract:In Nordic countries, distribution networks are unEarthed or compensated. Earth Faults, particularly in compensated networks, provide Fault currents that are low compared to the load currents. Identification of the Faulty feeder is therefore difficult. A preliminary description of discrete wavelet transform (DWT)-Bayesian selectivity technique was introduced in reference 1 to identify the Faulty feeder. It was dependent on a conditional probabilistic method applied to transient features extracted by using the DWT. However, a practical setting for this technique has not yet been presented. Furthermore, its sensitivity is limited to 1.5-k Fault resistances, and is further reduced to 170 when considering current transformer and network noise. In this paper, the ratio between the absolute sums of the DWT detail level from each feeder is used as an input to the conditional probability approach, providing an enhanced selectivity decision. This input contributes to discriminating the Faulty feeder during high resistance Faults. The relay setting is introduced as a function of the number of feeders and their characteristic impedances, as the proposed algorithm is dependent on the discharge's initial transients. The performance is evaluated taking into account current-transformer and network noises. A digital implementation is experimentally verified by using two digital signal processing boards.
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evaluation of probabilistic based selectivity technique for Earth Fault Protection in mv networks
IEEE PowerTech Conference, 2009Co-Authors: Abdelsalam Elhaffar, Nagy I Elkalashy, Naser Tarhuni, Mohamed F Abdelfattah, Matti LehtonenAbstract:In [1], a Bayesian selectivity technique has been introduced to identify the Faulty feeder in compensated medium voltage (MV) networks. The proposed technique has been based on a conditional probabilistic method applied on transient features extracted from the residual currents only using the Discrete Wavelet Transform (DWT). In this paper, the performance of this selectivity technique is evaluated when the current transformers (CTs) impacts are considered. The CTs are modeled considering their frequency characteristics. Furthermore, network noises are added to the simulated signals. Therefore, the algorithm can be tested at different practical conditions, such as nonlinear characteristics of the measuring devices and the impact of noise as well. The Fault cases occurring at different locations in a compensated 20 kV network are simulated by ATP/EMTP. Results show a reduction in the algorithm sensitivity with considering CT and noise effectiveness.
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windowed standard deviation based transient feature extraction for Earth Fault Protection in mv networks
International Universities Power Engineering Conference, 2009Co-Authors: Nagy I Elkalashy, Abdelsalam Elhaffar, Matti Lehtonen, Mohamed F Abdelfattah, Naser TarhuniAbstract:In this paper, the windowed standard deviation (WSTD) is used to extract the initial transients created in residual current waveforms generated due to Earth Faults in Medium Voltage (MV) compensated networks. The sliding window width used for computing the standard deviation is evaluated from the frequency filter point of view. The Fault cases occurring in a compensated 20 kV network are simulated by ATP/EMTP concerning practical Fault case such as arcing Faults. Results provide evidence that the windowed standard deviation can be used to extract initial transients although they are non-stationary sinusoidal signals.
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DWT and Bayesian technique for enhancing Earth Fault Protection in MV networks
2009 IEEE PES Power Systems Conference and Exposition, 2009Co-Authors: Nagy I Elkalashy, Matti Lehtonen, Naser TarhuniAbstract:In this paper, a Bayesian selectivity technique is introduced to identify the Faulty feeder in compensated medium voltage (MV) networks. The proposed technique is based on a conditional probabilistic method applied on features extracted from the residual currents only using the Discrete Wavelet Transform (DWT). DWT enhances to localize initial transients generated in the network due to the Fault event. The absolute sum of a window of the DWT detail coefficient is used to detect the Fault. The conditional probability provides the selectivity decision. The Fault cases occurring at different locations in a compensated 20 kV network are simulated by ATP/EMTP concerning practical Fault case such as arcing Faults. Test results corroborate the efficacy of proposed technique.
Raul Vargas - One of the best experts on this subject based on the ideXlab platform.
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analysis of a stator Earth Fault Protection system of a medium voltage converter fed synchronous motor
IEEE Industry Applications Society Annual Meeting, 2010Co-Authors: J Pontt, Raul VargasAbstract:For grinding aplications cycloconverter-fed gearless mill drives are being applied with increasing powers and new risks emerge with the systems scaling-up. Traditional parasitic second order effects may be not neglected, like thermal expansions, electromagnetic effects and EMC emissions. In this frame, harmonics and partial discharges of windings in medium voltage converter-fed machines build additional leakage current background that masks eventual phase insulation failures or produce nuissance trips in the protective system. Despite these perturbations, for reliable operation, the electrical Protection system must detect properly a phase-to-ground Fault of the motor in the 100% length of stator winding with the trade-off between sensititvity ad insensitivity. This work presents a study and discussion based on modeling and simulation for assessing the limitations and range of application of a 100% Earth Fault Protection configuration, considering the operation of this Protection acting also as Earth leakage Protection.
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IAS - Analysis of a Stator Earth Fault Protection System of a Medium Voltage Converter-Fed Synchronous Motor
2010 IEEE Industry Applications Society Annual Meeting, 2010Co-Authors: J Pontt, Raul VargasAbstract:For grinding aplications cycloconverter-fed gearless mill drives are being applied with increasing powers and new risks emerge with the systems scaling-up. Traditional parasitic second order effects may be not neglected, like thermal expansions, electromagnetic effects and EMC emissions. In this frame, harmonics and partial discharges of windings in medium voltage converter-fed machines build additional leakage current background that masks eventual phase insulation failures or produce nuissance trips in the protective system. Despite these perturbations, for reliable operation, the electrical Protection system must detect properly a phase-to-ground Fault of the motor in the 100% length of stator winding with the trade-off between sensititvity ad insensitivity. This work presents a study and discussion based on modeling and simulation for assessing the limitations and range of application of a 100% Earth Fault Protection configuration, considering the operation of this Protection acting also as Earth leakage Protection.
Rafiqul Islam - One of the best experts on this subject based on the ideXlab platform.
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restricted Earth Fault Protection with superconducting Fault current limiter for 100 stator winding
2013 International Conference on Electrical Information and Communication Technology (EICT), 2014Co-Authors: Elias Khan, Apurbo Biswas, Rafiqul IslamAbstract:Conventional Restricted Earth Fault Protection provides Protection about 80 to 90% of generator stator winding against Earth Fault when neutral of generator is Earthed through a resistance. In this paper, superconducting Fault current limiter an innovative device is used along with restricted Earth Fault Protection to provide 100% stator Earth Fault Protection. A specific generator is considered which is provided with restricted Earth Fault Protection to protect 90% of its winding against Earth Fault. Then a resistive SFCL is applied in the protective scheme replacing the neutral Earthed resistance to a lower value than the previous one. It is found that excellent operational characteristics of SFCL facilitate the restricted Earth Fault relay to operate from very beginning to the end of the generator winding and provide 100% stator Earth Fault Protection.
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Restricted Earth Fault Protection with superconducting Fault current limiter for 100% stator winding
2013 International Conference on Electrical Information and Communication Technology (EICT), 2014Co-Authors: Elias Khan, Apurbo Biswas, Rafiqul IslamAbstract:Conventional Restricted Earth Fault Protection provides Protection about 80 to 90% of generator stator winding against Earth Fault when neutral of generator is Earthed through a resistance. In this paper, superconducting Fault current limiter an innovative device is used along with restricted Earth Fault Protection to provide 100% stator Earth Fault Protection. A specific generator is considered which is provided with restricted Earth Fault Protection to protect 90% of its winding against Earth Fault. Then a resistive SFCL is applied in the protective scheme replacing the neutral Earthed resistance to a lower value than the previous one. It is found that excellent operational characteristics of SFCL facilitate the restricted Earth Fault relay to operate from very beginning to the end of the generator winding and provide 100% stator Earth Fault Protection.
Nagy I Elkalashy - One of the best experts on this subject based on the ideXlab platform.
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bayesian selectivity technique for Earth Fault Protection in medium voltage networks
IEEE Transactions on Power Delivery, 2010Co-Authors: Nagy I Elkalashy, Abdelsalam Elhaffar, Tamer A Kawady, Naser Tarhuni, Matti LehtonenAbstract:In Nordic countries, distribution networks are unEarthed or compensated. Earth Faults, particularly in compensated networks, provide Fault currents that are low compared to the load currents. Identification of the Faulty feeder is therefore difficult. A preliminary description of discrete wavelet transform (DWT)-Bayesian selectivity technique was introduced in reference 1 to identify the Faulty feeder. It was dependent on a conditional probabilistic method applied to transient features extracted by using the DWT. However, a practical setting for this technique has not yet been presented. Furthermore, its sensitivity is limited to 1.5-k Fault resistances, and is further reduced to 170 when considering current transformer and network noise. In this paper, the ratio between the absolute sums of the DWT detail level from each feeder is used as an input to the conditional probability approach, providing an enhanced selectivity decision. This input contributes to discriminating the Faulty feeder during high resistance Faults. The relay setting is introduced as a function of the number of feeders and their characteristic impedances, as the proposed algorithm is dependent on the discharge's initial transients. The performance is evaluated taking into account current-transformer and network noises. A digital implementation is experimentally verified by using two digital signal processing boards.
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evaluation of probabilistic based selectivity technique for Earth Fault Protection in mv networks
IEEE PowerTech Conference, 2009Co-Authors: Abdelsalam Elhaffar, Nagy I Elkalashy, Naser Tarhuni, Mohamed F Abdelfattah, Matti LehtonenAbstract:In [1], a Bayesian selectivity technique has been introduced to identify the Faulty feeder in compensated medium voltage (MV) networks. The proposed technique has been based on a conditional probabilistic method applied on transient features extracted from the residual currents only using the Discrete Wavelet Transform (DWT). In this paper, the performance of this selectivity technique is evaluated when the current transformers (CTs) impacts are considered. The CTs are modeled considering their frequency characteristics. Furthermore, network noises are added to the simulated signals. Therefore, the algorithm can be tested at different practical conditions, such as nonlinear characteristics of the measuring devices and the impact of noise as well. The Fault cases occurring at different locations in a compensated 20 kV network are simulated by ATP/EMTP. Results show a reduction in the algorithm sensitivity with considering CT and noise effectiveness.
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windowed standard deviation based transient feature extraction for Earth Fault Protection in mv networks
International Universities Power Engineering Conference, 2009Co-Authors: Nagy I Elkalashy, Abdelsalam Elhaffar, Matti Lehtonen, Mohamed F Abdelfattah, Naser TarhuniAbstract:In this paper, the windowed standard deviation (WSTD) is used to extract the initial transients created in residual current waveforms generated due to Earth Faults in Medium Voltage (MV) compensated networks. The sliding window width used for computing the standard deviation is evaluated from the frequency filter point of view. The Fault cases occurring in a compensated 20 kV network are simulated by ATP/EMTP concerning practical Fault case such as arcing Faults. Results provide evidence that the windowed standard deviation can be used to extract initial transients although they are non-stationary sinusoidal signals.
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DWT and Bayesian technique for enhancing Earth Fault Protection in MV networks
2009 IEEE PES Power Systems Conference and Exposition, 2009Co-Authors: Nagy I Elkalashy, Matti Lehtonen, Naser TarhuniAbstract:In this paper, a Bayesian selectivity technique is introduced to identify the Faulty feeder in compensated medium voltage (MV) networks. The proposed technique is based on a conditional probabilistic method applied on features extracted from the residual currents only using the Discrete Wavelet Transform (DWT). DWT enhances to localize initial transients generated in the network due to the Fault event. The absolute sum of a window of the DWT detail coefficient is used to detect the Fault. The conditional probability provides the selectivity decision. The Fault cases occurring at different locations in a compensated 20 kV network are simulated by ATP/EMTP concerning practical Fault case such as arcing Faults. Test results corroborate the efficacy of proposed technique.
