When fault occurs on cross-coupling autotransformer(AT)power supply traction network,the up-line and down-line feeder circuit breakers in the traction substation trip at the same time without selectivity,which leads t...When fault occurs on cross-coupling autotransformer(AT)power supply traction network,the up-line and down-line feeder circuit breakers in the traction substation trip at the same time without selectivity,which leads to an extended power failure.Based on equivalent circuit and Kirchhoff’s current law,the feeder current characteristic in the substation,AT station and sectioning post when T-R fault,F-R fault,and T-F fault occur are analyzed and their expressions are obtained.When the traction power supply system is equipped with wide-area protection measurement and control system,the feeder protection device in each station collects the feeder currents in other two stations through the wide-area protection channel and a wide-area current differential protection scheme based on the feeder current characteristic is proposed.When a short-circuit fault occurs in the power supply arm,all the feeder protection devices in each station receive the feeder currents with time stamp in other two stations.After data synchronous processing and logic judgment,the fault line of the power supply arm can be identified and isolated quickly.The simulation result based on MATLAB/Simulink shows that the power supply arm protection scheme based on wide-area current differential has good fault discrimination ability under different fault positions,transition resistances,and fault types.The verification of measured data shows that the novel protection scheme will not be affected by the special working conditions of the electrical multiple unit(EMU),and reliability,selectivity,and rapidity of relay protection are all improved.展开更多
This paper analyzes characteristics of multi type current transformers hybrid operation for each branch of the bus and their effects on differential protection of the bus. By theoretically analyzing transmission chara...This paper analyzes characteristics of multi type current transformers hybrid operation for each branch of the bus and their effects on differential protection of the bus. By theoretically analyzing transmission characteristics of multi type current transformers and their influence factors, we study the dynamic model testing method of multi type current transformers for the bus, and design 3 kinds of testing schemes by making the equivalent model based on the field of P-level current transformer, TPY-level current transformer and electronic current transformer, and build the hybrid operation testing platform of multi type current transformers. Finally, we compare and analyze the transmission characteristics difference of multi type current transformers on the same branch and the characteristics difference of hybrid operation in two successive external faults, analyze the cause behind the differences, and put forward the corresponding improvement measures.展开更多
Recently,differential privacy algorithms based on deep learning have become increasingly mature.Previous studies provide privacy mostly by adding differential privacy noise to the gradient,but it will reduce the accur...Recently,differential privacy algorithms based on deep learning have become increasingly mature.Previous studies provide privacy mostly by adding differential privacy noise to the gradient,but it will reduce the accuracy,and it is difficult to balance privacy and accuracy.In this paper,the DP-ASSGD algo-rithm is proposed to counterpoise privacy and accuracy.The convergence speed is improved,the number of optimized iterations is decreased,and the privacy loss is significantly reduced.On the other hand,by using the postprocessing immunity characteristics of the differential privacy model,the Laplace smoothing mecha-nism is added to make the training process more stable and the generalization ability stronger.The experiment uses the MNIST dataset,with the same privacy budget,and compared with the existing differential privacy algorithms,the accu-racy is improved by 1.8%on average.When achieving the same accuracy,the DP-ASSGD algorithm consumes less privacy budget.展开更多
The emergence of distributed generators has changed the operational mode and fault characteristics of the distribu-tion network,in a way which can severely influence protection.This paper proposes a d-axis-based curre...The emergence of distributed generators has changed the operational mode and fault characteristics of the distribu-tion network,in a way which can severely influence protection.This paper proposes a d-axis-based current differential protection scheme.The d-axis current characteristics of inverter-interfaced distributed generators and synchronous generators are analyzed.The differential protection criterion using sampling values of the d-axis current component is then constructed.Compared to conventional phase-based current differential protection,the proposed protection reduces the number of required communication channels,and is suitable for distribution networks with inverter-interfaced distributed generators with complex fault characteristics.Finally,a 10 kV active distribution network model is built in the PSCAD platform and protection prototypes are developed in RTDS.Superior sensitivity and fast speed are verified by simulation and RTDS-based tests.展开更多
We propose a new scheme for transformer differential protection. This scheme uses different characteristics of the differential currents waveforms (DCWs) under internal fault and magnetizing inrush current conditions....We propose a new scheme for transformer differential protection. This scheme uses different characteristics of the differential currents waveforms (DCWs) under internal fault and magnetizing inrush current conditions. The scheme is based on choosing an appropriate feature of the waveform and monitoring it during the post-disturbance instants. For this purpose, the signal feature is quantified by a discrimination function (DF). Discrimination between internal faults and magnetizing inrush currents is carried out by tracking the signs of three decision-making functions (DMFs) computed from the DFs for three phases. We also present a new algorithm related to the general scheme. The algorithm is based on monitoring the second derivative sign of DCW. The results show that all types of internal faults, even those accompanied by the magnetizing inrush, can be correctly identified from the inrush conditions about half a cycle after the occurrence of a disturbance. Another advantage of the proposed method is that the fault detection algorithm does not depend on the selection of thresholds. Furthermore, the proposed algorithm does not require burdensome computations.展开更多
With respect to sensitivity,selectivity and speed of operation,the current differential scheme is a better way to protect transmission lines than overcurrent and distance-based schemes.However,the protection scheme ca...With respect to sensitivity,selectivity and speed of operation,the current differential scheme is a better way to protect transmission lines than overcurrent and distance-based schemes.However,the protection scheme can be severely influenced by the Line Charging Capacitive Current(LCCC)with increased voltage level and Current Transformer(CT)saturation under external close-in faults.This paper presents a new UHV/EHV current-based protection scheme using the ratio of phasor summation of the two-end currents to the local end current,instead of summation of the two-end currents,to discriminate the internal faults.The accuracy and effectiveness of the proposed protection technique are tested on the 110 kV Western System Coordinating Council(WSCC)9-bus system using PSCAD/MATLAB.The simulation results confirm the reliable operation of the proposed scheme during internal/external faults and its independence from fault location,fault resistance,type of fault,and variations in source impedance.Finally,the effectiveness of the proposed scheme is also verified with faults during power swing and in series compensated lines.展开更多
基金supported by the Natural Science Foundation of Sichuan Province(No.2022NSFSC0405).
文摘When fault occurs on cross-coupling autotransformer(AT)power supply traction network,the up-line and down-line feeder circuit breakers in the traction substation trip at the same time without selectivity,which leads to an extended power failure.Based on equivalent circuit and Kirchhoff’s current law,the feeder current characteristic in the substation,AT station and sectioning post when T-R fault,F-R fault,and T-F fault occur are analyzed and their expressions are obtained.When the traction power supply system is equipped with wide-area protection measurement and control system,the feeder protection device in each station collects the feeder currents in other two stations through the wide-area protection channel and a wide-area current differential protection scheme based on the feeder current characteristic is proposed.When a short-circuit fault occurs in the power supply arm,all the feeder protection devices in each station receive the feeder currents with time stamp in other two stations.After data synchronous processing and logic judgment,the fault line of the power supply arm can be identified and isolated quickly.The simulation result based on MATLAB/Simulink shows that the power supply arm protection scheme based on wide-area current differential has good fault discrimination ability under different fault positions,transition resistances,and fault types.The verification of measured data shows that the novel protection scheme will not be affected by the special working conditions of the electrical multiple unit(EMU),and reliability,selectivity,and rapidity of relay protection are all improved.
文摘This paper analyzes characteristics of multi type current transformers hybrid operation for each branch of the bus and their effects on differential protection of the bus. By theoretically analyzing transmission characteristics of multi type current transformers and their influence factors, we study the dynamic model testing method of multi type current transformers for the bus, and design 3 kinds of testing schemes by making the equivalent model based on the field of P-level current transformer, TPY-level current transformer and electronic current transformer, and build the hybrid operation testing platform of multi type current transformers. Finally, we compare and analyze the transmission characteristics difference of multi type current transformers on the same branch and the characteristics difference of hybrid operation in two successive external faults, analyze the cause behind the differences, and put forward the corresponding improvement measures.
文摘Recently,differential privacy algorithms based on deep learning have become increasingly mature.Previous studies provide privacy mostly by adding differential privacy noise to the gradient,but it will reduce the accuracy,and it is difficult to balance privacy and accuracy.In this paper,the DP-ASSGD algo-rithm is proposed to counterpoise privacy and accuracy.The convergence speed is improved,the number of optimized iterations is decreased,and the privacy loss is significantly reduced.On the other hand,by using the postprocessing immunity characteristics of the differential privacy model,the Laplace smoothing mecha-nism is added to make the training process more stable and the generalization ability stronger.The experiment uses the MNIST dataset,with the same privacy budget,and compared with the existing differential privacy algorithms,the accu-racy is improved by 1.8%on average.When achieving the same accuracy,the DP-ASSGD algorithm consumes less privacy budget.
基金supported by China Southern Power Grid Technology Project.
文摘The emergence of distributed generators has changed the operational mode and fault characteristics of the distribu-tion network,in a way which can severely influence protection.This paper proposes a d-axis-based current differential protection scheme.The d-axis current characteristics of inverter-interfaced distributed generators and synchronous generators are analyzed.The differential protection criterion using sampling values of the d-axis current component is then constructed.Compared to conventional phase-based current differential protection,the proposed protection reduces the number of required communication channels,and is suitable for distribution networks with inverter-interfaced distributed generators with complex fault characteristics.Finally,a 10 kV active distribution network model is built in the PSCAD platform and protection prototypes are developed in RTDS.Superior sensitivity and fast speed are verified by simulation and RTDS-based tests.
文摘We propose a new scheme for transformer differential protection. This scheme uses different characteristics of the differential currents waveforms (DCWs) under internal fault and magnetizing inrush current conditions. The scheme is based on choosing an appropriate feature of the waveform and monitoring it during the post-disturbance instants. For this purpose, the signal feature is quantified by a discrimination function (DF). Discrimination between internal faults and magnetizing inrush currents is carried out by tracking the signs of three decision-making functions (DMFs) computed from the DFs for three phases. We also present a new algorithm related to the general scheme. The algorithm is based on monitoring the second derivative sign of DCW. The results show that all types of internal faults, even those accompanied by the magnetizing inrush, can be correctly identified from the inrush conditions about half a cycle after the occurrence of a disturbance. Another advantage of the proposed method is that the fault detection algorithm does not depend on the selection of thresholds. Furthermore, the proposed algorithm does not require burdensome computations.
文摘With respect to sensitivity,selectivity and speed of operation,the current differential scheme is a better way to protect transmission lines than overcurrent and distance-based schemes.However,the protection scheme can be severely influenced by the Line Charging Capacitive Current(LCCC)with increased voltage level and Current Transformer(CT)saturation under external close-in faults.This paper presents a new UHV/EHV current-based protection scheme using the ratio of phasor summation of the two-end currents to the local end current,instead of summation of the two-end currents,to discriminate the internal faults.The accuracy and effectiveness of the proposed protection technique are tested on the 110 kV Western System Coordinating Council(WSCC)9-bus system using PSCAD/MATLAB.The simulation results confirm the reliable operation of the proposed scheme during internal/external faults and its independence from fault location,fault resistance,type of fault,and variations in source impedance.Finally,the effectiveness of the proposed scheme is also verified with faults during power swing and in series compensated lines.