This paper outlines the significance of enhancing the instantaneous protection reliability of low voltage circuit breakers and describes their main failure modes. The instantaneous failure mechanism of low voltage cir...This paper outlines the significance of enhancing the instantaneous protection reliability of low voltage circuit breakers and describes their main failure modes. The instantaneous failure mechanism of low voltage circuit breakers was analyzed so that measures to improve instantaneous protection reliability can be determined. Furthermore, the theory of the instantaneous characteristics calibration device for low voltage circuit breakers and the method of eliminating the non-periodic component of test current are given in detail. Finally, the test results are presented.展开更多
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 a DFIG （doubly fed induction generator） WT （wind turbine） fault current after a symmetrical network voltage dip. The goal is to identify the factors determining how fast the first zero crossing...This paper analyzes a DFIG （doubly fed induction generator） WT （wind turbine） fault current after a symmetrical network voltage dip. The goal is to identify the factors determining how fast the first zero crossings of the fault current occur. This is an important subject because the ftmdamental property of the CB （circuit breaker） is that it breaks the current when the current is very near zero. The study was conducted using a hardware-in-the-loop test environment constructed using two real time simulators （dSPACE and RTDS） and a commercial protection relay. It is found that the reactive current injection during a voltage dip demanded by the grid codes enhances the operation of the WT protection because the zero crossings of the currents through CB are attained earlier. In addition, the size of the crowbar resistance has a significant influence on the zero crossings.展开更多
A crowbar impulse current circuit for testing the switch-type surge protective device （SPD） is presented. The crowbar circuit consists of a computer control circuit, a trigger voltage pulse generator, a main dischar...A crowbar impulse current circuit for testing the switch-type surge protective device （SPD） is presented. The crowbar circuit consists of a computer control circuit, a trigger voltage pulse generator, a main discharging switch, and a crowbar pseudospark switch. The active trigger technology was studied in the crowbar impulse current circuit. The circuit monitors the main discharging current and generates a trigger signal at a proper time for the crowbar pseudospark switch operation. The trigger characteristics of the main discharge switch and the crowbar pseu- dospark switch were investigated. By monitoring the preset applied capacitor voltage, the gap distance of the main discharging switch could be adjusted to ensure a discharging delay time less than 2 μs. Equipped with a surface ttashover trigger device made of high relative perimittivity dielectric material BaTiO3 （εr = 3460）, the discharge delay time of the crowbar pseudospark switch is less than 85 ns, and the minimum operating voltage is less than 1% of its self-breakdown voltage. With a storage capacitor of 9 μF , an inductor of 18 μH and a crowbar pseudospark switch, a load of 30 mΩ and an applied capacitor voltage of 40 kV, an impulse current waveform of maximum 25 kA was generated with a rise time and time to half peak value of 17.2 μs and 336μs respectively.展开更多
High quality electricity services are the prime objectives in the modern power systems around the world. One of the main players to achieve this is the protection of the system which needs to be fast, reliable and cos...High quality electricity services are the prime objectives in the modern power systems around the world. One of the main players to achieve this is the protection of the system which needs to be fast, reliable and cost effective. The study about the protection of the Low Voltage (LV) CIGRE distribution grid and networks like this has been proposed in this paper. The main objective of this paper is to develop protection against short circuit faults which might appear anywhere in the network. The protection of the power networks that comprises of renewable energy generation units is complicated because of the bidirectional flow of the current and is a challenge for the protection engineers. The selection of the protection devices in this paper is made to protect the network against faults in grid connected and island mode of operation. Ultra-fast fuses are proposed in order to protect the inverters used for Photovoltaic (PV) and battery applications. The disconnection of the PV solar panels when in island mode is made by proposing switch disconnecting devices. ABB is currently using these kinds of disconnection devices for the purpose of protecting solar panels against over voltages in the case of islanding. The over speed protection of the existing Wind Turbine Generator (WTG) in the CIGRE network in case of grid loss is also proposed in this paper.展开更多
To study the effects of wind generators on distribution system protection,the short-circuit current(SCC) characteristics of wind generators is important.Although there are many researches on the issue,a clear agreemen...To study the effects of wind generators on distribution system protection,the short-circuit current(SCC) characteristics of wind generators is important.Although there are many researches on the issue,a clear agreement has not been reached so far.The SCC characteristics for different wind generators are studied.PSCAD simulation is performed in the same system integrated with different kinds of wind generators,and their results are compared with those reported in IEEE papers.The detection possibility by overcurrent relay(OCR)is discussed based on the simulation results.展开更多
A big step forward to improve power system monitoring and performance, continued load growth without a corresponding increase in transmission resources has resulted in reduced operational margins for many power system...A big step forward to improve power system monitoring and performance, continued load growth without a corresponding increase in transmission resources has resulted in reduced operational margins for many power systems worldwide and has led to operation of power systems closer to their stability limits and to power exchange in new patterns. These issues, as well as the on-going worldwide trend towards deregulation of the entire industry on the one hand and the increased need for accurate and better network monitoring on the other hand, force power utilities exposed to this pressure to demand new solutions for wide area monitoring, protection and control. Wide-area monitoring, protection, and control require communicating the specific-node information to a remote station but all information should be time synchronized so that to neutralize the time difference between information. It gives a complete simultaneous snap shot of the power system. The conventional system is not able to satisfy the time-synchronized requirement of power system. Phasor Measurement Unit (PMU) is enabler of time-synchronized measurement, it communicate the synchronized local information to remote station.展开更多
柔性光学电流互感器(flexible optical current transformer,FOCT)在水电领域的推广应用,为奇数多分支发电机主保护定量化改造奠定了基础。经内部故障的全面分析计算,某每相7分支的大型发电机主保护定量化设计结果推荐采用“3-1-3”分...柔性光学电流互感器(flexible optical current transformer,FOCT)在水电领域的推广应用,为奇数多分支发电机主保护定量化改造奠定了基础。经内部故障的全面分析计算,某每相7分支的大型发电机主保护定量化设计结果推荐采用“3-1-3”分支分组方式,相应的主保护配置方案保护死区虽小(0.5%)但对相间短路存在保护死区——发生在每相未装设分支电流互感器(TA)的第4分支之间,利用柔性光学TA绕制灵活的特点,通过增设每相第4分支的光学TA及对应的不完全纵差保护即可消除上述相间短路保护死区。上述主保护定量化改造思路将为后续奇数多分支大型发电机的技术改造提供借鉴。展开更多
柔性直流电网的故障检测与保护研究是当前电力领域的关键技术。直流电网发生故障时,故障电流迅速上升导致电网系统设备损坏且稳定性下降,因此对故障保护系统的快速性和可靠性要求极高。通过比较线路上限流电感电压值在故障前后的变化,...柔性直流电网的故障检测与保护研究是当前电力领域的关键技术。直流电网发生故障时,故障电流迅速上升导致电网系统设备损坏且稳定性下降,因此对故障保护系统的快速性和可靠性要求极高。通过比较线路上限流电感电压值在故障前后的变化,提出一种利用限流电感两端电压比值实现线路故障识别的方法。在PSCAD/EMTDC仿真平台建立四端模块化多电平换流器型柔性直流输电(modular multilevel converter high voltage direct current,MMC-HVDC)电网模型,对所提出的方法进行故障启动、类型识别和极线选择验证。在故障被正确识别后,相应的直流断路器(DC circuit breaker,DCCB)能够正确动作并隔离故障。此外,还对系统的性能指标以及故障过渡电阻值、故障后系统的噪声、故障距离和通信误差方面因素进行可行性分析。研究结果表明,所提出的故障保护方案能够准确识别并且快速隔离故障,从而保障电网安全稳定运行。展开更多
The insulated gate bipolar transistor(IGBT) has become the most popular controllable power switching device in the design of power electronics industry.As the interface of power circuit and control circuit in power so...The insulated gate bipolar transistor(IGBT) has become the most popular controllable power switching device in the design of power electronics industry.As the interface of power circuit and control circuit in power source, the IGBT drive circuit should be with short transition time and the function of isolating safely and monitoring correctly the short-circuit and over-voltage fault.This paper presents the short-circuit protection theory and relative parameter selecting rules,based on the research on 2QD30A17K-I,the representative of high voltage and high power driver.展开更多
This paper discusses a preferable solution to mitigate the CT （current transformer） saturation problem, and at same time, reduce the accuracy errors when considering the selection of CTs for installation on the medi...This paper discusses a preferable solution to mitigate the CT （current transformer） saturation problem, and at same time, reduce the accuracy errors when considering the selection of CTs for installation on the medium voltage switchgear of a nuclear power plant. This consideration is important for both measurement and protection functions of the digital protective relays. This is a study to ascertain the best options for a suitable solution to prevent CT saturation in relations to its protective capabilities during short circuit fault without compromising the CT accuracy class during normal operation of the system, while ensuring its conformity to the design requirement is within limit. The advantages of current transformers have proven not only to be reliable and safe, but also are of easy handling, reduction of the cost and components on the MV （medium voltage） switchgear. The purpose of this research is to identify best approach to resolve the existing problems in the current protection system. With the view of LPCT （low power current transformer） which has been newly constructed by few manufacturers to provide good protection and a wide range of measuring function without errors, some other solutions will be considered in this research.展开更多
基金Project (No. 043804411) supported by the Tianjin Natural ScienceFoundation, China
文摘This paper outlines the significance of enhancing the instantaneous protection reliability of low voltage circuit breakers and describes their main failure modes. The instantaneous failure mechanism of low voltage circuit breakers was analyzed so that measures to improve instantaneous protection reliability can be determined. Furthermore, the theory of the instantaneous characteristics calibration device for low voltage circuit breakers and the method of eliminating the non-periodic component of test current are given in detail. Finally, the test results are presented.
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 a DFIG （doubly fed induction generator） WT （wind turbine） fault current after a symmetrical network voltage dip. The goal is to identify the factors determining how fast the first zero crossings of the fault current occur. This is an important subject because the ftmdamental property of the CB （circuit breaker） is that it breaks the current when the current is very near zero. The study was conducted using a hardware-in-the-loop test environment constructed using two real time simulators （dSPACE and RTDS） and a commercial protection relay. It is found that the reactive current injection during a voltage dip demanded by the grid codes enhances the operation of the WT protection because the zero crossings of the currents through CB are attained earlier. In addition, the size of the crowbar resistance has a significant influence on the zero crossings.
文摘A crowbar impulse current circuit for testing the switch-type surge protective device （SPD） is presented. The crowbar circuit consists of a computer control circuit, a trigger voltage pulse generator, a main discharging switch, and a crowbar pseudospark switch. The active trigger technology was studied in the crowbar impulse current circuit. The circuit monitors the main discharging current and generates a trigger signal at a proper time for the crowbar pseudospark switch operation. The trigger characteristics of the main discharge switch and the crowbar pseu- dospark switch were investigated. By monitoring the preset applied capacitor voltage, the gap distance of the main discharging switch could be adjusted to ensure a discharging delay time less than 2 μs. Equipped with a surface ttashover trigger device made of high relative perimittivity dielectric material BaTiO3 （εr = 3460）, the discharge delay time of the crowbar pseudospark switch is less than 85 ns, and the minimum operating voltage is less than 1% of its self-breakdown voltage. With a storage capacitor of 9 μF , an inductor of 18 μH and a crowbar pseudospark switch, a load of 30 mΩ and an applied capacitor voltage of 40 kV, an impulse current waveform of maximum 25 kA was generated with a rise time and time to half peak value of 17.2 μs and 336μs respectively.
文摘High quality electricity services are the prime objectives in the modern power systems around the world. One of the main players to achieve this is the protection of the system which needs to be fast, reliable and cost effective. The study about the protection of the Low Voltage (LV) CIGRE distribution grid and networks like this has been proposed in this paper. The main objective of this paper is to develop protection against short circuit faults which might appear anywhere in the network. The protection of the power networks that comprises of renewable energy generation units is complicated because of the bidirectional flow of the current and is a challenge for the protection engineers. The selection of the protection devices in this paper is made to protect the network against faults in grid connected and island mode of operation. Ultra-fast fuses are proposed in order to protect the inverters used for Photovoltaic (PV) and battery applications. The disconnection of the PV solar panels when in island mode is made by proposing switch disconnecting devices. ABB is currently using these kinds of disconnection devices for the purpose of protecting solar panels against over voltages in the case of islanding. The over speed protection of the existing Wind Turbine Generator (WTG) in the CIGRE network in case of grid loss is also proposed in this paper.
基金supported by the Power Generation & Electricity Delivery of the Korea Institute of Energy Technology and Planning(KETEP)grant funded by the Korea Government Ministry of Knowledge Economy(No.2009T100200067)
文摘To study the effects of wind generators on distribution system protection,the short-circuit current(SCC) characteristics of wind generators is important.Although there are many researches on the issue,a clear agreement has not been reached so far.The SCC characteristics for different wind generators are studied.PSCAD simulation is performed in the same system integrated with different kinds of wind generators,and their results are compared with those reported in IEEE papers.The detection possibility by overcurrent relay(OCR)is discussed based on the simulation results.
文摘A big step forward to improve power system monitoring and performance, continued load growth without a corresponding increase in transmission resources has resulted in reduced operational margins for many power systems worldwide and has led to operation of power systems closer to their stability limits and to power exchange in new patterns. These issues, as well as the on-going worldwide trend towards deregulation of the entire industry on the one hand and the increased need for accurate and better network monitoring on the other hand, force power utilities exposed to this pressure to demand new solutions for wide area monitoring, protection and control. Wide-area monitoring, protection, and control require communicating the specific-node information to a remote station but all information should be time synchronized so that to neutralize the time difference between information. It gives a complete simultaneous snap shot of the power system. The conventional system is not able to satisfy the time-synchronized requirement of power system. Phasor Measurement Unit (PMU) is enabler of time-synchronized measurement, it communicate the synchronized local information to remote station.
文摘柔性光学电流互感器(flexible optical current transformer,FOCT)在水电领域的推广应用,为奇数多分支发电机主保护定量化改造奠定了基础。经内部故障的全面分析计算,某每相7分支的大型发电机主保护定量化设计结果推荐采用“3-1-3”分支分组方式,相应的主保护配置方案保护死区虽小(0.5%)但对相间短路存在保护死区——发生在每相未装设分支电流互感器(TA)的第4分支之间,利用柔性光学TA绕制灵活的特点,通过增设每相第4分支的光学TA及对应的不完全纵差保护即可消除上述相间短路保护死区。上述主保护定量化改造思路将为后续奇数多分支大型发电机的技术改造提供借鉴。
文摘柔性直流电网的故障检测与保护研究是当前电力领域的关键技术。直流电网发生故障时,故障电流迅速上升导致电网系统设备损坏且稳定性下降,因此对故障保护系统的快速性和可靠性要求极高。通过比较线路上限流电感电压值在故障前后的变化,提出一种利用限流电感两端电压比值实现线路故障识别的方法。在PSCAD/EMTDC仿真平台建立四端模块化多电平换流器型柔性直流输电(modular multilevel converter high voltage direct current,MMC-HVDC)电网模型,对所提出的方法进行故障启动、类型识别和极线选择验证。在故障被正确识别后,相应的直流断路器(DC circuit breaker,DCCB)能够正确动作并隔离故障。此外,还对系统的性能指标以及故障过渡电阻值、故障后系统的噪声、故障距离和通信误差方面因素进行可行性分析。研究结果表明,所提出的故障保护方案能够准确识别并且快速隔离故障,从而保障电网安全稳定运行。
文摘The insulated gate bipolar transistor(IGBT) has become the most popular controllable power switching device in the design of power electronics industry.As the interface of power circuit and control circuit in power source, the IGBT drive circuit should be with short transition time and the function of isolating safely and monitoring correctly the short-circuit and over-voltage fault.This paper presents the short-circuit protection theory and relative parameter selecting rules,based on the research on 2QD30A17K-I,the representative of high voltage and high power driver.
文摘This paper discusses a preferable solution to mitigate the CT （current transformer） saturation problem, and at same time, reduce the accuracy errors when considering the selection of CTs for installation on the medium voltage switchgear of a nuclear power plant. This consideration is important for both measurement and protection functions of the digital protective relays. This is a study to ascertain the best options for a suitable solution to prevent CT saturation in relations to its protective capabilities during short circuit fault without compromising the CT accuracy class during normal operation of the system, while ensuring its conformity to the design requirement is within limit. The advantages of current transformers have proven not only to be reliable and safe, but also are of easy handling, reduction of the cost and components on the MV （medium voltage） switchgear. The purpose of this research is to identify best approach to resolve the existing problems in the current protection system. With the view of LPCT （low power current transformer） which has been newly constructed by few manufacturers to provide good protection and a wide range of measuring function without errors, some other solutions will be considered in this research.
